This section provides a detailed definition of the syntax and semantics of each node in the specification.
Anchor
Anchor {
eventIn MFNode addChildren
eventIn MFNode removeChildren
exposedField MFNode children []
exposedField SFString description ""
exposedField MFString parameter []
exposedField MFString url []
field SFVec3f bboxCenter 0 0 0
field SFVec3f bboxSize -1 -1 -1
}
The Anchor grouping node causes a URL to be fetched over the network when the viewer activates (e.g. clicks) some geometry contained within the Anchor's children. If the URL pointed to is a legal VRML world, then that world replaces the world which the Anchor is a part of. If non-VRML data type is fetched, it is up to the browser to determine how to handle that data; typically, it will be passed to an appropriate general viewer.
Exactly how a user activates a child of the Anchor depends on the pointing device and is determined by the VRML browser. Typically, clicking with the pointing device will result in the new scene replacing the current scene. An Anchor with an empty ("") url does nothing when its children are chosen. See "Concepts - Sensors and Pointing Device Sensors" for a description of how multiple Anchors and pointing device sensors are resolved on activation.
See the "Concepts - Grouping and Children Nodes" section for a description of children, addChildren, and removeChildren fields and eventIns.
The description field in the Anchor allows for a prompt to be displayed as an alternative to the URL in the url field. Ideally, browsers will allow the user to choose the description, the URL, or both to be displayed for a candidate Anchor.
The parameter exposed field may be used to supply any additional information to be interpreted by the VRML or HTML browser. Each string should consist of "keyword=value" pairs. For example, some browsers allow the specification of a 'target' for a link, to display a link in another part of the HTML document; the parameter field is then:
Anchor {
parameter [ "target=name_of_frame" ]
...
}
An Anchor may be used to bind the initial Viewpoint in a world by specifying a URL ending with "#ViewpointName", where "ViewpointName" is the name of a viewpoint defined in the file. For example:
Anchor {
url "http://www.school.edu/vrml/someScene.wrl#OverView"
children Shape { geometry Box {} }
}
specifies an anchor that loads the file "someScene.wrl", and binds the initial user view to the Viewpoint named "OverView" (when the Box is activated). If the named Viewpoint is not found in the file, then ignore it and load the file with the default Viewpoint. If no world is specified, then this means that the Viewpoint specified should be bound (set_bind TRUE). For example:
Anchor {url "#Doorway"children Shape { geometry Sphere {} }}
binds viewer to the viewpoint defined by the "Doorway" viewpoint in the current world when the sphere is activated. In this case, if the Viewpoint is not found, then do nothing on activation.
See "Concepts - URLS and URNs" for more details on the url field.
The bboxCenter and bboxSize fields specify a bounding box that encloses the Anchor's children. This is a hint that may be used for optimization purposes. If the specified bounding box is smaller than the actual bounding box of the children at any time, then the results are undefined. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and if needed must be calculated by the browser. See "Concepts - Bounding Boxes" for a description of bboxCenter and bboxSize fields.
Appearance
Appearance {
exposedField SFNode material NULL
exposedField SFNode texture NULL
exposedField SFNode textureTransform NULL
}
The Appearance node specifies the visual properties of geometry by defining the material and texture nodes. The value for each of the fields in this node can be NULL. However, if the field is non-NULL, it must contain one node of the appropriate type.
The material field, if specified, must contain a Material node. If the material field is NULL or unspecified, lighting is off (all lights are ignored during rendering of the object that references this Appearance) and the unlit object color is (0, 0, 0) - see "Concepts - Lighting Model" for details of the VRML lighting model.
The texture field, if specified, must contain one of the various types of texture nodes (ImageTexture, MovieTexture, or PixelTexture). If the texture node is NULL or unspecified, the object that references this Appearance is not textured.
The textureTransform field, if specified, must contain a TextureTransform node. If the texture field is NULL or unspecified, or if the textureTransform is NULL or unspecified, the textureTransform field has no effect.
AudioClip
AudioClip {
exposedField SFString description ""
exposedField SFBool loop FALSE
exposedField SFFloat pitch 1.0
exposedField SFTime startTime 0
exposedField SFTime stopTime 0
exposedField MFString url []
eventOut SFTime duration_changed
eventOut SFBool isActive
}
An AudioClip node specifies audio data that can be referenced by other nodes that require an audio source.
The description field is a textual description of the audio source. A browser is not required to display the description field but may choose to do so in addition to or in place of playing the sound.
The url field specifies the URL from which the sound is loaded. Browsers shall support at least the wavefile format in uncompressed PCM format [WAVE]. It is recommended that browsers also support the MIDI file type 1 sound format [MIDI]. MIDI files are presumed to use the General MIDI patch set. See the section on URLs and URNs in "Concepts - URLs and URNs" for details on the url field. Results are not defined when the URL references unsupported data types.
The loop, startTime, and stopTime exposedFields and the isActive eventOut, and their affects on the AudioClip node, are discussed in detail in the "Concepts - Time Dependent Nodes" section. The "cycle" of an AudioClip is the length of time in seconds for one playing of the audio at the specified pitch.
The pitch field specifies a multiplier for the rate at which sampled sound is played. Only positive values are valid for pitch (a value of zero or less will produce undefined results). Changing the pitch field affects both the pitch and playback speed of a sound. A set_pitch event to an active AudioClip is ignored (and no pitch_changed eventOut is generated). If pitch is set to 2.0, the sound should be played one octave higher than normal and played twice as fast. For a sampled sound, the pitch field alters the sampling rate at which the sound is played. The proper implementation of the pitch control for MIDI (or other note sequence sound clip) is to multiply the tempo of the playback by the pitch value and adjust the MIDI Coarse Tune and Fine Tune controls to achieve the proper pitch change. The pitch field must be > 0.0.
A duration_changed event is sent whenever there is a new value for the "normal" duration of the clip. Typically this will only occur when the current url in use changes and the sound data has been loaded, indicating that the clip is playing a different sound source. The duration is the length of time in seconds for one cycle of the audio for a pitch set to 1.0. Changing the pitch field will not trigger a duration_changed event. A duration value of -1 implies the sound data has not yet loaded or the value is unavailable for some reason.
The isActive eventOut can be used by other nodes to determine if the clip is currently active. If an AudioClip is active, then it should be playing the sound corresponding to the sound time (i.e., in the sound's local time system with sample 0 at time 0):
fmod (now - startTime, duration / pitch).
Background
Background {
eventIn SFBool set_bind
exposedField MFFloat groundAngle []
exposedfield MFColor groundColor []
exposedField MFString backUrl []
exposedField MFString bottomUrl []
exposedField MFString frontUrl []
exposedField MFString leftUrl []
exposedField MFString rightUrl []
exposedField MFString topUrl []
exposedField MFFloat skyAngle []
exposedField MFColor skyColor [ 0 0 0 ]
eventOut SFBool isBound
}
The Background node is used to specify a color backdrop that simulates ground and sky, as well as a background texture, or panorama, that is placed behind all geometry in the scene and in front of the ground and sky. Background nodes are specified in the local coordinate system and are affected by the accumulated rotation of their parents (see below).
Background nodes are bindable nodes (see "Concepts - Bindable Children Nodes"). There exists a Background stack, in which the top-most Background on the stack is the currently active Background and thus applied to the view. To move a Background to the top of the stack, a TRUE value is sent to the set_bind eventIn. Once active, the Background is then bound to the browsers view. A FALSE value of set_bind, removes the Background from the stack and unbinds it from the browser viewer. See "Concepts - Bindable Children Nodes" for more details on the the bind stack.
The ground and sky backdrop is conceptually a partial sphere (i.e. ground) enclosed inside of a full sphere (i.e. sky) in the local coordinate system, with the viewer placed at the center of the spheres. Both spheres have infinite radius (epsilon apart), and each is painted with concentric circles of interpolated color perpendicular to the local Y axis of the sphere. The Background node is subject to the accumulated rotations of its parent transformations - scaling and translation transformations are ignored. The sky sphere is always slightly farther away from the viewer than the ground sphere - the ground appears in front of the sky in cases where they overlap.
The skyColor field specifies the color of the sky at the various angles on the sky sphere. The first value of the skyColor field specifies the color of the sky at 0.0 degrees, the north pole (i.e. straight up from the viewer). The skyAngle field specifies the angles from the north pole in which concentric circles of color appear - the north pole of the sphere is implicitly defined to be 0.0 degrees, the natural horizon at pi/2 radians, and the south pole is pi radians. skyAngle is restricted to increasing values in the range 0.0 to pi. There must be one more skyColor value than there are skyAngle values - the first color value is the color at the north pole, which is not specified in the skyAngle field. If the last skyAngle is less than pi, then the color band between the last skyAngle and the south pole is clamped to the last skyColor. The sky color is linearly interpolated between the specified skyColor values.
The groundColor field specifies the color of the ground at the various angles on the ground sphere. The first value of the groundColor field specifies the color of the ground at 0.0 degrees, the south pole (i.e. straight down). The groundAngle field specifies the angles from the south pole that the concentric circles of color appear - the south pole of the sphere is implicitly defined at 0.0 degrees. groundAngle is restricted to increasing values in the range 0.0 to pi. There must be one more groundColor values than there are groundAngle values - the first color value is for the south pole which is not specified in the groundAngle field. If the last groundAngle is less than pi (it usually is), then the region between the last groundAngle and the north pole is invisible. The ground color is linearly interpolated between the specified groundColor values.
The backUrl, bottomUrl, frontUrl, leftUrl, rightUrl, and topUrl fields specify a set of images that define a background panorama, between the ground/sky backdrop and the world's geometry. The panorama consists of six images, each of which is mapped onto the faces of an infinitely large cube centered in the local coordinate system. The images are applied individually to each face of the cube; the entire image goes on each face. On the front, back, right, and left faces of the cube, when viewed from the inside with the Y-axis up, the texture is mapped onto each face with the same orientation as the if image was displayed normally in 2D. On the top face of the cube, when viewed from the inside looking up along the +Y axis with the +Z axis as the view up direction, the texture is mapped onto the face with the same orientation as the if image was displayed normally in 2D. On the bottom face of the box, when viewed from the inside down the -Y axis with the -Z axis as the view up direction, the texture is mapped onto the face with the same orientation as the if image was displayed normally in 2D.
Alpha values in the panorama images (i.e. two or four component images) specify that the panorama is semi-transparent or transparent in regions, allowing the groundColor and skyColor to be visible. One component images are displayed in greyscale; two component images are displayed in greyscale with alpha transparency; three component images are displayed in full RGB color; four component images are displayed in full RGB color with alpha transparency. Often, the bottomUrl and topUrl images will not be specified, to allow sky and ground to show. The other four images may depict surrounding mountains or other distant scenery. Browsers are required to support the JPEG [JPEG] and PNG [PNG] image file formats, and in addition, may support any other image formats. Support for the GIF [GIF] format (including transparent backgrounds) is recommended. See the section "Concepts - URLS and URNs" for details on the url fields.
Panorama images may be one component (greyscale), two component (greyscale plus alpha), three component (full RGB color), or four-component (full RGB color plus alpha).
Ground colors, sky colors, and panoramic images do not translate with respect to the viewer, though they do rotate with respect to the viewer. That is, the viewer can never get any closer to the background, but can turn to examine all sides of the panorama cube, and can look up and down to see the concentric rings of ground and sky (if visible).
Background is not affected by Fog. Therefore, if a Background is active (i.e bound) while a Fog is active, then the Background will be displayed with no fogging effects. It is the author's responsibility to set the Background values to match the Fog (e.g. ground colors fade to fog color with distance and panorama images tinted with fog color).
The first Background node found during reading of the world is automatically bound (receives set_bind TRUE) and is used as the initial background when the world is loaded.
Billboard
Billboard {
eventIn MFNode addChildren
eventIn MFNode removeChildren
exposedField SFVec3f axisOfRotation 0 1 0
exposedField MFNode children []
field SFVec3f bboxCenter 0 0 0
field SFVec3f bboxSize -1 -1 -1
}
The Billboard node is a grouping node which modifies its coordinate system so that the billboard node's local Z-axis turns to point at the viewer. The Billboard node has children which may be other grouping or leaf nodes.
The axisOfRotation field specifies which axis to use to perform the rotation. This axis is defined in the local coordinates of the Billboard node. The default (0,1,0) is useful for objects such as images of trees and lamps positioned on a ground plane. But when an object is oriented at an angle, for example, on the incline of a mountain, then the axisOfRotation may also need to be oriented at a similar angle.
A special case of billboarding is screen-alignment -- the object rotates to always stay aligned with the viewer even when the viewer elevates, pitches and rolls. This special case is distinguished by setting the axisOfRotation to (0, 0, 0).
To rotate the Billboard to face the viewer, determine the line between the Billboard's origin and the viewer's position; call this the billboard-to-viewer line. The axisOfRotation and the billboard-to-viewer line define a plane. The local z-axis of the Billboard is then rotated into that plane, pivoting around the axisOfRotation.
If the axisOfRotation and the billboard-to-viewer line are coincident (the same line), then the plane cannot be established, and the rotation results of the Billboard are undefined. For example, if the axisOfRotation is set to (0,1,0) (Y-axis) and the viewer flies over the Billboard and peers directly down the Y-axis the results are undefined.
Multiple instances of Billboards (DEF/USE) operate as expected - each instance rotates in its unique coordinate system to face the viewer.
See the "Concepts - Grouping and Children Nodes" section for a description the children, addChildren, and removeChildren fields and eventIns.
The bboxCenter and bboxSize fields specify a bounding box that encloses the Billboard's children. This is a hint that may be used for optimization purposes. If the specified bounding box is smaller than the actual bounding box of the children at any time, then the results are undefined. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and if needed must be calculated by the browser. See "Concepts - Bounding Boxes" for a description of bboxCenter and bboxSize fields.
Box
Box {
field SFVec3f size 2 2 2
}
The Box node specifies a rectangular parallelepiped box in the local coordinate system centered at (0,0,0) in the local coordinate system and aligned with the coordinate axes. By default, the box measures 2 units in each dimension, from -1 to +1. The Box's size field specifies the extents of the the box along the X, Y, and Z axes respectively and must be greater than 0.0.
Textures are applied individually to each face of the box; the entire untransformed texture goes on each face. On the front, back, right, and left faces of the box, when viewed from the outside with the Y-axis up, the texture is mapped onto each face with the same orientation as the if image was displayed in normally 2D. On the top face of the box, when viewed from the outside along the +Y axis looking down with the -Z axis as the view up direction, the texture is mapped onto the face with the same orientation as if the image were displayed normally in 2D. On the bottom face of the box, when viewed from the outside along the -Y axis looking up with the +Z axis as the view up direction, the texture is mapped onto the face with the same orientation as if the image were displayed normally in 2D. TextureTransform affects the texture coordinates of the Box.
The Box geometry is considered to be solid and thus requires outside faces only. When viewed from the inside the results are undefined.
Collision
Collision {
eventIn MFNode addChildren
eventIn MFNode removeChildren
exposedField MFNode children []
exposedField SFBool collide TRUE
field SFVec3f bboxCenter 0 0 0
field SFVec3f bboxSize -1 -1 -1
field SFNode proxy NULL
eventOut SFTime collideTime
}
By default, all objects in the scene are collidable. Browser shall detect geometric collisions between the user's avatar (see NavigationInfo) and the scene's geometry, and prevent the avatar from `entering' the geometry. The Collision node is grouping node that may turn off collision detection for its descendants, specify alternative objects to use for collision detection, and send events signaling that a collision has occurred between the user's avatar and the Collision group's geometry or alternate. If there are no Collision nodes specified in a scene, browsers shall detect collision with all objects during navigation.
See the "Concepts - Grouping and Children Nodes" section for a description the children, addChildren, and removeChildren fields and eventIns.
The Collision node's collide field enables and disables collision detection. If collide is set to FALSE, the children and all descendants of the Collision node will not be checked for collision, even though they are drawn. This includes any descendant Collision nodes that have collide set to TRUE - (i.e. setting collide to FALSE turns it off for every node below it).
Collision nodes with the collide field set to TRUE detect the nearest collision with their descendant geometry (or proxies). Note that not all geometry is collidable - see each geometry node's sections for details. When the nearest collision is detected, the collided Collision node sends the time of the collision through its collideTime eventOut. This behavior is recursive - if a Collision node contains a child, descendant, or proxy (see below) that is a Collision node, and both Collisions detect that a collision has occurred, then both send a collideTime event out at the same time, and so on.
The bboxCenter and bboxSize fields specify a bounding box that encloses the Collision's children. This is a hint that may be used for optimization purposes. If the specified bounding box is smaller than the actual bounding box of the children at any time, then the results are undefined. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and if needed must be calculated by the browser. See "Concepts - Bounding Boxes" for a description of the bboxCenter and bboxSize fields.
The collision proxy, defined in the proxy field, is a legal child node, (see "Concepts - Grouping and Children Nodes"), that is used as a substitute for the Collision's children during collision detection. The proxy is used strictly for collision detection - it is not drawn.
If the value of the collide field is FALSE, then collision detection is not performed with the children or proxy descendant nodes. If the root node of a scene is a Collision node with the collide field set to FALSE, then collision detection is disabled for the entire scene, regardless of whether descendent Collision nodes have set collide TRUE.
If the value of the collide field is TRUE and the proxy field is non-NULL, then the proxy field defines the scene which collision detection is performed. If the proxy value is NULL, the children of the collision node are collided against.
If proxy is specified, then any descendant children of the Collision node are ignored during collision detection. If children is empty, collide is TRUE and proxy is specified, then collision detection is done against the proxy but nothing is displayed (i.e. invisible collision objects).
The collideTime eventOut generates an event specifying the time when the user's avatar (see NavigationInfo) intersects the collidable children or proxy of the Collision node. An ideal implementation computes the exact time of intersection. Implementations may approximate the ideal by sampling the positions of collidable objects and the user. Refer to the NavigationInfo node for parameters that control the user's size.
Browsers are responsible for defining the navigation behavior when collisions occur. For example, when the user comes sufficiently close to an object to trigger a collision, the browser may have the user bounce off the object, come to a stop, or glide along the surface.
Color
Color {
exposedField MFColor color []
}
This node defines a set of RGB colors to be used in the fields of another node.
Color nodes are only used to specify multiple colors for a single piece of geometry, such as a different color for each face or vertex of an IndexedFaceSet. A Material node is used to specify the overall material parameters of a lighted geometry. If both a Material and a Color node are specified for a geometry, the colors should ideally replace the diffuse component of the material.
Textures take precedence over colors; specifying both a Texture and a Color node for a geometry will result in the Color node being ignored. See "Concepts - Lighting Model" for details on lighting equations.
ColorInterpolator
ColorInterpolator {
eventIn SFFloat set_fraction
exposedField MFFloat key []
exposedField MFColor keyValue []
eventOut SFColor value_changed
}
This node interpolates among a set of MFColor key values, to produce an SFColor (RGB) value_changed event. The number of colors in the keyValue field must be equal to the number of keyframes in the key field. The keyValue field and value_changed events are defined in RGB color space. A linear interpolation, using the value of set_fraction as input, is performed in HSV space.
Refer to "Concepts - Interpolators" for a more detailed discussion of interpolators.
Cone
Cone {
field SFFloat bottomRadius 1
field SFFloat height 2
field SFBool side TRUE
field SFBool bottom TRUE
}
The Cone node specifies a cone which is centered in the local coordinate system and whose central axis is aligned with the local Y-axis. The bottonRadius field specifies the radius of the cone's base, and the height field specifies the height of the cone from the center of the base to the apex. By default, the cone has a radius of 1.0 at the bottom and a height of 2.0, with its apex at y=1 and its bottom at y=-1. Both bottomRadius and height must be greater than 0.0.
The side field specifies whether sides of the cone are created, and the bottom field specifies whether the bottom cap of the cone is created. A value of TRUE specifies that this part of the cone exists, while a value of FALSE specifies that this part does not exist (not rendered). Parts with field values of FALSE are not collided with during collision detection.
When a texture is applied to the sides of the cone, the texture wraps counterclockwise (from above) starting at the back of the cone. The texture has a vertical seam at the back in the YZ plane, from the apex (0, height/2, 0) to the point (0, 0, -r). For the bottom cap, a circle is cut out of the unit texture square centered at (0, -height/2, 0) with dimensions (2 * bottomRadius) by (2 * bottomRadius). The bottom cap texture appears right side up when the top of the cone is rotated towards the -Z axis. TextureTransform affects the texture coordinates of the Cone.
The Cone geometry is considered to be solid and thus requires outside faces only. When viewed from the inside the results are undefined.
Coordinate
Coordinate {
exposedField MFVec3f point []
}
This node defines a set of 3D coordinates to be used in the coord field of vertex-based geometry nodes (such as IndexedFaceSet, IndexedLineSet, and PointSet).
CoordinateInterpolator
CoordinateInterpolator {
eventIn SFFloat set_fraction
exposedField MFFloat key []
exposedField MFVec3f keyValue []
eventOut MFVec3f value_changed
}
This node linearly interpolates among a set of MFVec3f value. This would be appropriate for interpolating Coordinate positions for a geometric morph.
The number of coordinates in the keyValue field must be an integer multiple of the number of keyframes in the key field; that integer multiple defines how many coordinates will be contained in the value_changed events.
Refer to "Concepts - Interpolators" for a more detailed discussion of interpolators.
Cylinder
Cylinder {
field SFBool bottom TRUE
field SFFloat height 2
field SFFloat radius 1
field SFBool side TRUE
field SFBool top TRUE
}
The Cylinder node specifies a capped cylinder centered at (0,0,0) in the local coordinate system and with a central axis oriented along the local Y-axis. By default, the cylinder is sized at -1 to +1 in all three dimensions. The radius field specifies the cylinder's radius and the height field specifies the cylinder's height along the central axis. Both radius and height must be greater than 0.0.
The cylinder has three parts: the side, the top (Y = +height) and the bottom (Y = -height). Each part has an associated SFBool field that indicates whether the part exists (TRUE) or does not exist (FALSE). If the parts do not exist, the they are not considered during collision detection.
When a texture is applied to a cylinder, it is applied differently to the sides, top, and bottom. On the sides, the texture wraps counterclockwise (from above) starting at the back of the cylinder. The texture has a vertical seam at the back, intersecting the YZ plane. For the top and bottom caps, a circle is cut out of the unit texture square centered at (0, +/- height, 0) with dimensions 2*radius by 2*radius. The top texture appears right side up when the top of the cylinder is tilted toward the +Z axis, and the bottom texture appears right side up when the top of the cylinder is tilted toward the -Z axis. TextureTransform affects the texture coordinates of the Cylinder.
The Cylinder geometry is considered to be solid and thus requires outside faces only. When viewed from the inside the results are undefined.
CylinderSensor
CylinderSensor {
exposedField SFBool autoOffset TRUE
exposedField SFFloat diskAngle 0.262
exposedField SFBool enabled TRUE
exposedField SFFloat maxAngle -1
exposedField SFFloat minAngle 0
exposedField SFFloat offset 0
eventOut SFBool isActive
eventOut SFRotation rotation_changed
eventOut SFVec3f trackPoint_changed
}
The CylinderSensor maps pointing device (e.g. mouse or wand) motion into a rotation on an invisible cylinder that is aligned with the Y axis of its local space.
The enabled exposed field enables and disables the CylinderSensor - if TRUE, the sensor reacts appropriately to user events, if FALSE, the sensor does not track user input or send output events. If enabled receives a FALSE event and isActive is TRUE, the sensor becomes disabled and deactivated, and outputs an isActive FALSE event. If enabled receives a TRUE event the sensor is enabled and ready for user activation.
The CylinderSensor generates events if the pointing device is activated while over any descendant geometry nodes of its parent group and then moved while activated. Typically, the pointing device is a 2D device such as a mouse. The pointing device is considered to be moving within a plane at a fixed distance from the viewer and perpendicular to the line of sight; this establishes a set of 3D coordinates for the pointer. If a 3D pointer is in use, then the sensor generates events only when the pointer is within the user's field of view. In either case, the pointing device is considered to "pass over" geometry when that geometry is intersected by a line extending from the viewer and passing through the pointer's 3D coordinates. If multiple sensors' geometry intersect this line (hereafter called the bearing), only the nearest will be eligible to generate events.
Upon activation of the pointing device (e.g. mouse button down) over the sensor's geometry, an isActive TRUE event is sent. The angle between the bearing vector and the local Y axis of the CylinderSensor determines whether the sides of the invisible cylinder or the caps (disks) are used for manipulation. If the angle is less than the diskAngle, then the geometry is treated as an infinitely large disk and dragging motion is mapped into a rotation around the local Y axis of the sensor's coordinate system. The feel of the rotation is as if you were rotating a dial or crank. Using the right-hand rule, the X axis of the sensor's local coordinate system, (defined by parents), represents the zero rotation value around the sensor's local Y axis. For each subsequent position of the bearing, a rotation_changed event is output which corresponds to the angle between the local X axis and the vector defined by the intersection point and the nearest point on the local Y axis, plus the offset value. trackPoint_changed events reflect the unclamped drag position on the surface of this disk. When the pointing device is deactivated and autoOffset is TRUE, offset is set to the last rotation angle and an offset_changed event is generated. See "Concepts - Drag Sensors" for more details on autoOffset and offset_changed.
If angle between the bearing vector and the local Y axis of the CylinderSensor is greater than or equal to diskAngle, then the sensor behaves like a cylinder or rolling pin. The shortest distance between the point of intersection (between the bearing and the sensor's geometry) and the Y axis of the parent group's local coordinate system determines the radius of an invisible cylinder used to map pointing device motion, and mark the zero rotation value. For each subsequent position of the bearing, a rotation_changed event is output which corresponds to a relative rotation from the original intersection, plus the offset value. trackPoint_changed events reflect the unclamped drag position on the surface of this cylinder. When the pointing device is deactivated and autoOffset is TRUE, offset is set to the last rotation angle and an offset_changed event is generated. See "Concepts - Drag Sensors" for more details.
When the sensor generates an isActive TRUE event, it grabs all further motion events from the pointing device until it releases and generates an isActive FALSE event (other pointing device sensors cannot generate events during this time). Motion of the pointing device while isActive is TRUE is referred to as a "drag". If a 2D pointing device is in use, isActive events will typically reflect the state of the primary button associated with the device (i.e. isActive is TRUE when the primary button is pressed, and FALSE when not released). If a 3D pointing device (e.g. wand) is in use, isActive events will typically reflect whether the pointer is within or in contact with the sensor's geometry.
While the pointing device is activated, trackPoint_changed and rotation_changed events are output and are interpreted from pointing device motion based on the sensor's local coordinate system at the time of activation. trackPoint_changed events represent the unclamped intersection points on the surface of the invisible cylinder or disk. If the initial angle results in cylinder rotation (as opposed to disk behavior) and if the pointing device is dragged off the cylinder while activated, browsers may interpret this in several ways (e.g. clamp all values to the cylinder, continue to rotate as the point is dragged away from the cylinder, etc.). Each movement of the pointing device, while isActive is TRUE, generates trackPoint_changed and rotation_changed events.
minAngle and maxAngle may be set to clamp rotation_changed events to a range of values (measured in radians about the local Z and Y axis as appropriate). If minAngle is greater than maxAngle, rotation_changed events are not clamped.
See "Concepts - Pointing Device Sensors and Drag Sensors" for more details.
DirectionalLight
DirectionalLight {
exposedField SFFloat ambientIntensity 0
exposedField SFColor color 1 1 1
exposedField SFVec3f direction 0 0 -1
exposedField SFFloat intensity 1
exposedField SFBool on TRUE
}
The DirectionalLight node defines a directional light source that illuminates along rays parallel to a given 3-dimensional vector. See "Concepts - Lights" for a definition of the ambientIntensity, color, intensity, and on fields.
The direction field specifies the direction vector within the local coordinate system that the light illuminates in. Light is emitted along parallel rays from an infinite distance away. A directional light source illuminates only the objects in its enclosing parent group. The light may illuminate everything within this coordinate system, including all children and descendants of its parent group. The accumulated transformations of the parent nodes affect the light.
See "Concepts - Lighting Model"for a precise description of VRML's lighting equations.
Some low-end renderers do not support the concept of per-object lighting. This means that placing DirectionalLights inside local coordinate systems, which implies lighting only the objects beneath the Transform with that light, is not supported in all systems. For the broadest compatibility, lights should be placed at outermost scope.
ElevationGrid
ElevationGrid {
eventIn MFFloat set_height
exposedField SFNode color NULL
exposedField SFNode normal NULL
exposedField SFNode texCoord NULL
field MFFloat height []
field SFBool ccw TRUE
field SFBool colorPerVertex TRUE
field SFFloat creaseAngle 0
field SFBool normalPerVertex TRUE
field SFBool solid TRUE
field SFInt32 xDimension 0
field SFFloat xSpacing 0.0
field SFInt32 zDimension 0
field SFFloat zSpacing 0.0
}
The ElevationGrid node specifies a uniform rectangular grid of varying height in the XZ plane of the local coordinate system. The geometry is described by a scalar array of height values that specify the height of a rectangular surface above each point of the grid.
The xDimension and zDimension fields indicate the number of dimensions of the grid height array in the X and Z directions. Both xDimension and zDimension must be > 1. The vertex locations for the rectangles are defined by the height field and the xSpacing and zSpacing fields:
Thus, the vertex corresponding to the point, P[i, j], on the grid is placed at:
P[i,j].x = xSpacing * i
P[i,j].y = height[ i + j * zDimension]
P[i,j].z = zSpacing * j
where 0<i<xDimension and 0<j<zDimension.
The set_height eventIn allows the height MFFloat field to be changed to allow animated ElevationGrids.
The default texture coordinates range from [0,0] at the first vertex to [1,1] at the last vertex. The S texture coordinate will be aligned with X, and the T texture coordinate with Z.
The colorPerVertex field determines whether colors (if specified in the color field) should be applied to each vertex or each quadrilateral of the ElevationGrid. If colorPerVertex is FALSE and the color field is not NULL, then the color field must contain a Color node containing at least (xDimension-1)*(zDimension-1) colors. If colorPerVertex is TRUE and the color field is not NULL, then the color field must contain a Color node containing at least xDimension*zDimension colors.
See the "Concepts - Geometry" for a description of the ccw, solid, and creaseAngle fields.
By default, the rectangles are defined with a counterclockwise ordering, so the Y component of the normal is positive. Setting the ccw field to FALSE reverses the normal direction. Backface culling is enabled when the ccw field and the solid field are both TRUE (the default).
Extrusion
Extrusion {
eventIn MFVec2f set_crossSection
eventIn MFRotation set_orientation
eventIn MFVec2f set_scale
eventIn MFVec3f set_spine
field SFBool beginCap TRUE
field SFBool ccw TRUE
field SFBool convex TRUE
field SFFloat creaseAngle 0
field MFVec2f crossSection [ 1 1, 1 -1, -1 -1, -1 1, 1 1 ]
field SFBool endCap TRUE
field MFRotation orientation 0 0 1 0
field MFVec2f scale 1 1
field SFBool solid TRUE
field MFVec3f spine [ 0 0 0, 0 1 0 ]
}
The Extrusion node specifies geometric shapes based on a two dimensional cross section extruded along a three dimensional spine. The cross section can be scaled and rotated at each spine point to produce a wide variety of shapes.
An Extrusion is defined by a 2D crossSection piecewise linear curve (described as a series of connected vertices), a 3D spine piecewise linear curve (also described as a series of connected vertices), a list of 2D scale parameters, and a list of 3D orientation parameters. Shapes are constructed as follows: The cross-section curve, which starts as a curve in the XZ plane, is first scaled about the origin by the first scale parameter (first value scales in X, second value scales in Z). It is then rotated about the origin by the first orientation parameter, and translated by the vector given as the first vertex of the spine curve. It is then extruded through space along the first segment of the spine curve. Next, it is scaled and rotated by the second scale and orientation parameters and extruded by the second segment of the spine, and so on. The number of scale and orientation values shall equal the number of spine points, or contain one value that is applied to all points. The scale values must be > 0.
A transformed cross section is found for each joint (that is, at each vertex of the spine curve, where segments of the extrusion connect), and the joints and segments are connected to form the surface. No check is made for self-penetration. Each transformed cross section is determined as follows:
For all points other than the first or last: The tangent for spine[i] is found by normalizing the vector defined by (spine[i+1] - spine[i-1]).
If the spine curve is closed: The first and last points need to have the same tangent. This tangent is found as above, but using the points spine[0] for spine[i], spine[1] for spine[i+1] and spine[n-2] for spine[i-1], where spine[n-2] is the next to last point on the curve. The last point in the curve, spine[n-1], is the same as the first, spine[0].
If the spine curve is not closed: The tangent used for the first point is just the direction from spine[0] to spine[1], and the tangent used for the last is the direction from spine[n-2] to spine[n-1].
In the simple case where the spine curve is flat in the XY plane, these rotations are all just rotations about the Z axis. In the more general case where the spine curve is any 3D curve, you need to find the destinations for all 3 of the local X, Y, and Z axes so you can completely specify the rotation. The Z axis is found by taking the cross product of:
(spine[i-1] - spine[i]) and (spine[i+1] - spine[i]).
If the three points are collinear then this value is zero, so take the value from the previous point. Once you have the Z axis (from the cross product) and the Y axis (from the approximate tangent), calculate the X axis as the cross product of the Y and Z axes.
Surfaces of revolution: If the cross section is an approximation of a circle and the spine is straight, then the Extrusion is equivalent to a surface of revolution, where the scale parameters define the size of the cross section along the spine.
Cookie-cutter extrusions: If the scale is 1, 1 and the spine is straight, then the cross section acts like a cookie cutter, with the thickness of the cookie equal to the length of the spine.
Bend/twist/taper objects: These shapes are the result of using all fields. The spine curve bends the extruded shape defined by the cross section, the orientation parameters twist it around the spine, and the scale parameters taper it (by scaling about the spine).
Extrusion has three parts: the sides, the beginCap (the surface at the initial end of the spine) and the endCap (the surface at the final end of the spine). The caps have an associated SFBool field that indicates whether it exists (TRUE) or doesn't exist (FALSE).
When the beginCap or endCap fields are specified as TRUE, planar cap surfaces will be generated regardless of whether the crossSection is a closed curve. (If crossSection isn't a closed curve, the caps are generated as if it were -- equivalent to adding a final point to crossSection that's equal to the initial point. Note that an open surface can still have a cap, resulting (for a simple case) in a shape something like a soda can sliced in half vertically.) These surfaces are generated even if spine is also a closed curve. If a field value is FALSE, the corresponding cap is not generated.
Extrusion automatically generates its own normals. Orientation of the normals is determined by the vertex ordering of the triangles generated by Extrusion. The vertex ordering is in turn determined by the crossSection curve. If the crossSection is counterclockwise when viewed from the +Y axis, then the polygons will have counterclockwise ordering when viewed from 'outside' of the shape (and vice versa for clockwise ordered crossSection curves).
Texture coordinates are automatically generated by extrusions. Textures are mapped so that the coordinates range in the U direction from 0 to 1 along the crossSection curve (with 0 corresponding to the first point in crossSection and 1 to the last) and in the V direction from 0 to 1 along the spine curve (again with 0 corresponding to the first listed spine point and 1 to the last). When crossSection is closed, the texture has a seam that follows the line traced by the crossSection's start/end point as it travels along the spine. If the endCap and/or beginCap exist, the crossSection curve is uniformly scaled and translated so that the largest dimension of the cross-section (X or Z) produces texture coordinates that range from 0.0 to 1.0. The beginCap and endCap textures' S and T directions correspond to the X and Z directions in which the crossSection coordinates are defined.
See "Concepts - Geometry Nodes" for a description of the ccw, solid, convex, and creaseAngle fields.
Fog
Fog {
exposedField SFColor color 1 1 1
exposedField SFString fogType "LINEAR"
exposedField SFFloat visibilityRange 0
eventIn SFBool set_bind
eventOut SFBool isBound
}
The Fog node provides a way to simulate atmospheric effects by blending objects with the color specified by the color field based on the objects' distances from the viewer. The distances are calculated in the coordinate space of the Fog node. The visibilityRange specifies the distance (in the Fog node's coordinate space) at which objects are totally obscured by the fog. Objects located visibilityRange meters or more away from the viewer are drawn with a constant color of color. Objects very close to the viewer are blended very little with the fog color. A visibilityRange of 0.0 or less disables the Fog node. Note that visibilityRange is affected by the scaling transformations of the Fog node's parents - translations and rotations have no affect on visibilityRange.
Fog nodes are "Concepts - Bindable Children Nodes" and thus there exists a Fog stack, in which the top-most Fog node on the stack is currently active. To push a Fog node onto the top of the stack, a TRUE value is sent to the set_bind eventIn. Once active, the Fog is then bound to the browsers view. A FALSE value of set_bind, pops the Fog from the stack and unbinds it from the browser viewer. See "Concepts - Bindable Children Nodes" for more details on the the Fog stack.
The fogType field controls how much of the fog color is blended with the object as a function of distance. If fogType is "LINEAR" (the default), then the amount of blending is a linear function of the distance, resulting in a depth cuing effect. If fogType is "EXPONENTIAL" then an exponential increase in blending should be used, resulting in a more natural fog appearance.
For best visual results, the Background node (which is unaffected by the Fog node) should be the same color as the fog node. The Fog node can also be used in conjunction with the visibilityLimit field of NavigationInfo node to provide a smooth fade out of objects as they approach the far clipping plane.
See the section "Concepts - Lighting Model" for details on lighting calculations.
FontStyle
FontStyle {
field SFString family "SERIF"
field SFBool horizontal TRUE
field MFString justify "BEGIN"
field SFString language ""
field SFBool leftToRight TRUE
field SFFloat size 1.0
field SFFloat spacing 1.0
field SFString style "PLAIN"
field SFBool topToBottom TRUE
}
The FontStyle node defines the size, font family, and style of text's font, as well as the direction of the text strings and any specific language rendering techniques that must be used for non-English text. See Text node for application of FontStyle.
The size field specifies the height (in object space units) of glyphs rendered and determines the spacing of adjacent lines of text. All subsequent strings advance in either X or Y by -( size * spacing).
Font attributes are defined with the family and style fields. It is up to the browser to assign specific fonts to the various attribute combinations.
The family field specifies a case-sensitive SFString value that may be "SERIF" (the default) for a serif font such as Times Roman; "SANS" for a sans-serif font such as Helvetica; or "TYPEWRITER" for a fixed-pitch font such as Courier. A family value of empty quotes, "", is identical to "SERIF".
The style field specifies a case-sensitive SFString value that may be "PLAIN" (the default) for default plain type; "BOLD" for boldface type; "ITALIC" for italic type; or "BOLDITALIC" for bold and italic type. A style value of empty quotes, "", is identical to "PLAIN".
The horizontal, leftToRight, and topToBottom fields indicate the direction of the text. The horizontal field indicates whether the text advances horizontally in its major direction (horizontal = TRUE, the default) or vertically in its major direction (horizontal = FALSE). The leftToRight and topToBottom fields indicate direction of text advance in the major (characters within a single string) and minor (successive strings) axes of layout. Which field is used for the major direction and which is used for the minor direction is determined by the horizontal field.
For horizontal text (horizontal = TRUE), characters on each line of text advance in the positive X direction if leftToRight is TRUE or in the negative X direction if leftToRight is FALSE. Characters are advanced according to their natural advance width. Then each line of characters is advanced in the negative Y direction if topToBottom is TRUE or in the positive Y direction if topToBottom is FALSE. Lines are advanced by the amount of size * spacing.
For vertical text (horizontal = FALSE), characters on each line of text advance in the negative Y direction if topToBottom is TRUE or in the positive Y direction if topToBottom is FALSE. Characters are advanced according to their natural advance height. Then each line of characters is advanced in the positive X direction if leftToRight is TRUE or in the negative X direction if leftToRight is FALSE. Lines are advanced by the amount of size * spacing.
The justify field determines alignment of the above text layout relative to the origin of the object coordinate system. It is an MFString which can contain 2 values. The first value specifies alignment along the major axis and the second value specifies alignment along the minor axis, as determined by the horizontal field. A justify value of "" is equivalent to the default value. If the second string, minor alignment, is not specified then it defaults to the value "FIRST". Thus, justify values of "", "BEGIN", and ["BEGIN" "FIRST"] are equivalent.
The major alignment is along the X axis when horizontal is TRUE and along the Y axis when horizontal is FALSE. The minor alignment is along the Y axis when horizontal is TRUE and along the X axis when horizontal is FALSE. The possible values for each enumerant of the justify field are "FIRST", "BEGIN", "MIDDLE", and "END". For major alignment, each line of text is positioned individually according to the major alignment enumerant. For minor alignment, the block of text representing all lines together is positioned according to the minor alignment enumerant. The following table describes the behavior in terms of which portion of the text is at the origin:
| Enumerant | leftToRight = TRUE | leftToRight = FALSE |
| FIRST | Left edge of each line | Right edge of each line |
| BEGIN | Left edge of each line | Right edge of each line |
| MIDDLE | Centered about X-axis | Centered about X-axis |
| END | Right edge of each line | Left edge of each line |
| Enumerant | topToBottom = TRUE | topToBottom = FALSE |
| FIRST | Top edge of each line | Bottom edge of each line |
| BEGIN | Top edge of each line | Bottom edge of each line |
| MIDDLE | Centered about Y-axis | Center about Y-axis |
| END | Bottom edge of each line | Top edge of each line |
| Enumerant | topToBottom = TRUE | topToBottom = FALSE |
| FIRST | Baseline of first line | Baseline of first line |
| BEGIN | Top edge of first line | Bottom edge of first line |
| MIDDLE | Centered about Y-axis | Centered about Y-axis |
| END | Bottom edge of last line | Top edge of last line |
| Enumerant | leftToRight = TRUE | leftToRight = FALSE |
| FIRST | Left edge of first line | Right edge of first line |
| BEGIN | Left edge of first line | Right edge of first line |
| MIDDLE | Centered about X-axis | Centered about X-axis |
| END | Right edge of last line | Left edge of last line |
The default minor alignment is "FIRST". This is a special case of minor alignment when horizontal is TRUE. Text starts at the baseline at the Y-axis. In all other cases, :"FIRST" is identical to "BEGIN". In the following tables, each color-coded cross-hair indicates where the X and Y axes should be in relation to the text:
horizontal = TRUE:
horizontal = FALSE:
The language field specifies the context of the language for the text string. Due to the multilingual nature of the ISO 10646-1:1993, the language field is needed to provide a proper language attribute of the text string. The format is based on the POSIX locale specification as well as the RFC 1766: language[_territory]. The values for the language tag is based on the ISO 639, i.e. zh for Chinese, jp for Japanese, sc for Swedish. The territory tag is based on the ISO 3166 country code, i.e. TW is for Taiwan and CN for China for the "zh" Chinese language tag. If the language field is set to empty "", then local language bindings are used.
Please refer to these sites for more details:
http://www.chemie.fu-berlin.de/diverse/doc/ISO_639.html
http://www.chemie.fu-berlin.de/diverse/doc/ISO_3166.html
Group
Group {
eventIn MFNode addChildren
eventIn MFNode removeChildren
exposedField MFNode children []
field SFVec3f bboxCenter 0 0 0
field SFVec3f bboxSize -1 -1 -1
}
A Group node is equivalent to a Transform node, without the transformation fields.
See the "Concepts - Grouping and Children Nodes" section for a description of the children, addChildren, and removeChildren fields and eventIns.
The bboxCenter and bboxSize fields specify a bounding box that encloses the Group's children. This is a hint that may be used for optimization purposes. If the specified bounding box is smaller than the actual bounding box of the children at any time, then the results are undefined. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and if needed must be calculated by the browser. See "Concepts - Bounding Boxes" for a description of the bboxCenter and bboxSize fields.
ImageTexture
ImageTexture {
exposedField MFString url []
field SFBool repeatS TRUE
field SFBool repeatT TRUE
}
The ImageTexture node defines a texture map by specifying an image file and general parameters for mapping to geometry. Texture maps are defined in a 2D coordinate system, (s, t), that ranges from 0.0 to 1.0 in both directions. The bottom edge of the image corresponds to the S-axis of the texture map, and left edge of the image corresponds to the T-axis of the texture map. The lower-left pixel of the image corresponds to s=0, t=0, and the top-right pixel of the image corresponds to s=1, t=1.
The texture is read from the URL specified by the url field. To turn off texturing, set the url field to have no values ([]). Browsers are required to support the JPEG [JPEG] and PNG [PNG] image file formats, and in addition, may support any other image formats. Support for the GIF format [GIF] including transparent backgrounds is also recommended. See the section ""Concepts - URLS and URNs" for details on the url field.
Texture images may be one component (greyscale), two component (greyscale plus transparency), three component (full RGB color), or four-component (full RGB color plus transparency). An ideal VRML implementation will use the texture image to modify the diffuse color and transparency of an object's material (specified in a Material node), then perform any lighting calculations using the rest of the object's material properties with the modified diffuse color to produce the final image. The texture image modifies the diffuse color and transparency depending on how many components are in the image, as follows:
See "Concepts - Lighting Model" for details on lighting equations and the interaction between textures, materials, and geometries.
Browsers may approximate this ideal behavior to increase performance. One common optimization is to calculate lighting only at each vertex and combining the texture image with the color computed from lighting (performing the texturing after lighting). Another common optimization is to perform no lighting calculations at all when texturing is enabled, displaying only the colors of the texture image.
The repeatS and repeatT fields specify how the texture wraps in the S and T directions. If repeatS is TRUE (the default), the texture map is repeated outside the 0-to-1 texture coordinate range in the S direction so that it fills the shape. If repeatS is FALSE, the texture coordinates are clamped in the S direction to lie within the 0-to-1 range. The repeatT field is analogous to the repeatS field.
IndexedFaceSet
IndexedFaceSet {
eventIn MFInt32 set_colorIndex
eventIn MFInt32 set_coordIndex
eventIn MFInt32 set_normalIndex
eventIn MFInt32 set_texCoordIndex
exposedField SFNode color NULL
exposedField SFNode coord NULL
exposedField SFNode normal NULL
exposedField SFNode texCoord NULL
field SFBool ccw TRUE
field MFInt32 colorIndex []
field SFBool colorPerVertex TRUE
field SFBool convex TRUE
field MFInt32 coordIndex []
field SFFloat creaseAngle 0
field MFInt32 normalIndex []
field SFBool normalPerVertex TRUE
field SFBool solid TRUE
field MFInt32 texCoordIndex []
}
The IndexedFaceSet node represents a 3D shape formed by constructing faces (polygons) from vertices listed in the coord field. The coord field must contain a Coordinate node. IndexedFaceSet uses the indices in its coordIndex field to specify the polygonal faces. An index of -1 indicates that the current face has ended and the next one begins. The last face may (but does not have to be) followed by a -1. If the greatest index in the coordIndex field is N, then the Coordinate node must contain N+1 coordinates (indexed as 0-N). IndexedFaceSet is specified in the local coordinate system and is affected by parent transformations.
For descriptions of the coord, normal, and texCoord fields, see the Coordinate, Normal, and TextureCoordinate nodes.
See "Concepts - Lighting Model" for details on lighting equations and the interaction between textures, materials, and geometries.
If the color field is not NULL then it must contain a Color node, whose colors are applied to the vertices or faces of the IndexedFaceSet as follows:
If the normal field is NULL, then the browser should automatically generate normals, using creaseAngle to determine if and how normals are smoothed across shared vertices.
If the normal field is not NULL, then it must contain a Normal node, whose normals are applied to the vertices or faces of the IndexedFaceSet in a manner exactly equivalent to that described above for applying colors to vertices/faces.
If the texCoord field is not NULL, then it must contain a TextureCoordinate node. The texture coordinates in that node are applied to the vertices of the IndexedFaceSet as follows:
If the texCoord field is NULL, a default texture coordinate mapping is calculated using the bounding box of the shape. The longest dimension of the bounding box defines the S coordinates, and the next longest defines the T coordinates. If two or all three dimensions of the bounding box are equal, then ties should be broken by choosing the X, Y, or Z dimension in that order of preference. The value of the S coordinate ranges from 0 to 1, from one end of the bounding box to the other. The T coordinate ranges between 0 and the ratio of the second greatest dimension of the bounding box to the greatest dimension. See the figure below for an illustration of default texture coordinates for a simple box shaped IndexedFaceSet with a bounding box with X dimension twice as large as the Z dimension which is twice as large as the Y dimension:
See the introductory "Concepts - Geometry" section for a description of the ccw, solid, convex, and creaseAngle fields.
IndexedLineSet
IndexedLineSet {
eventIn MFInt32 set_colorIndex
eventIn MFInt32 set_coordIndex
exposedField SFNode color NULL
exposedField SFNode coord NULL
field MFInt32 colorIndex []
field SFBool colorPerVertex TRUE
field MFInt32 coordIndex []
}
The IndexedLineSet node represents a 3D geometry formed by constructing polylines from 3D points specified in the coord field. IndexedLineSet uses the indices in its coordIndex field to specify the polylines by connecting together points from the coord field. An index of -1 indicates that the current polyline has ended and the next one begins. The last polyline may (but does not have to be) followed by a -1. IndexedLineSet is specified in the local coordinate system and is affected by parent transformations.
The coord field specifies the 3D vertices of the line set and is specified by a Coordinate node.
Lines are not lit, not texture-mapped, or not collided with during collision detection.
If the color field is not NULL, it must contain a Color node, and the colors are applied to the line(s) as follows:
If the color field is NULL and there is a Material defined for the Appearance affecting this IndexedLineSet, then use the emissiveColor of the Material to draw the lines. See "Concepts - Lighting Model, Lighting Off" for details on lighting equations.
Inline
Inline {
exposedField MFString url []
field SFVec3f bboxCenter 0 0 0
field SFVec3f bboxSize -1 -1 -1
}
The Inline node is a grouping node that reads its children data from a location in the World Wide Web. Exactly when its children are read and displayed is not defined; reading the children may be delayed until the Inline is actually visible to the viewer. The url field specifies the URL containing the children. An Inline with an empty URL does nothing.
An Inline's URLs shall refer to a valid VRML file that contains a list of children nodes at the top level. See "Concepts - Grouping and Children Nodes". The results are undefined if the URL refers to a file that is not VRML or if the file contains non-children nodes at the top level.
If multiple URLs are specified, the browser may display a URL of a lower preference file while it is obtaining, or if it is unable to obtain the higher preference file. See "Concepts - URLS and URNs" for details on the url field and preference order.
The bboxCenter and bboxSize fields specify a bounding box that encloses the Inlines's children. This is a hint that may be used for optimization purposes. If the specified bounding box is smaller than the actual bounding box of the children at any time, then the results are undefined. A default bboxSize value, (-1 -1 -1), implies that the bounding box is not specified and if needed must be calculated by the browser. See "Concepts - Bounding Boxes" for a description of the bboxCenter and bboxSize fields.
LOD
LOD {
exposedField MFNode level []
field SFVec3f center 0 0 0
field MFFloat range []
}
The LOD node specifies various levels of detail or complexity for a given object, and provides hints for browsers to automatically choose the appropriate version of the object based on the distance from the user. The level field contains a list of nodes that represent the same object or objects at varying levels of detail, from highest to the lowest level of detail, and the range field specifies the ideal distances at which to switch between the levels. See the "Concepts - Grouping and Children Nodes" section for a details on the types of nodes that are legal values for level.
The center field is a translation offset in the local coordinate system that specifies the center of the LOD object for distance calculations. In order to calculate which level to display, first the distance is calculated from the viewpoint, transformed into the local coordinate space of the LOD node, (including any scaling transformations), to the center point of the LOD. If the distance is less than the first value in the range field, then the first level of the LOD is drawn. If between the first and second values in the range field, the second level is drawn, and so on.
If there are N values in the range field, the LOD shall have N+1 nodes in its level field. Specifying too few levels will result in the last level being used repeatedly for the lowest levels of detail; if more levels than ranges are specified, the extra levels will be ignored. The exception to this rule is to leave the range field empty, which is a hint to the browser that it should choose a level automatically to maintain a constant display rate. Each value in the range field should be greater than the previous value; otherwise results are undefined.
Authors should set LOD ranges so that the transitions from one level of detail to the next are smooth. Browsers may adjust which level of detail is displayed to maintain interactive frame rates, to display an already-fetched level of detail while a higher level of detail (contained in an Inline node) is fetched, or might disregard the author-specified ranges for any other implementation-dependent reason. For best results, specify ranges only where necessary, and nest LOD nodes with and without ranges. Browsers should try to honor the hints given by authors, and authors should try to give browsers as much freedom as they can to choose levels of detail based on performance.
LOD nodes are evaluated top-down in the scene graph. Only the descendants of the currently selected level are rendered. Note that all nodes under an LOD node continue to receive and send events (i.e. routes) regardless of which LOD level is active. For example, if an active TimeSensor is contained within an inactive level of an LOD, the TimeSensor sends events regardless of the LOD's state.
Material
Material {
exposedField SFFloat ambientIntensity 0.2
exposedField SFColor diffuseColor 0.8 0.8 0.8
exposedField SFColor emissiveColor 0 0 0
exposedField SFFloat shininess 0.2
exposedField SFColor specularColor 0 0 0
exposedField SFFloat transparency 0
}
The Material node specifies surface material properties for associated geometry nodes and are used by the VRML lighting equations during rendering. See "Concepts - Lighting Model" for a detailed description of the VRML lighting model equations.
All of the fields in the Material node range from 0.0 to 1.0.
The fields in the Material node determine the way light reflects off an object to create color:
For rendering systems that do not support the full OpenGL lighting model, the following simpler lighting model is recommended:
A transparency value of 0 is completely opaque, a value of 1 is completely transparent. Browsers need not support partial transparency, but should support at least fully transparent and fully opaque surfaces, treating transparency values >= 0.5 as fully transparent.
Issues for Low-End Rendering Systems. Many low-end PC rendering systems are not able to support the full range of the VRML material specification. For example, many systems do not render individual red, green and blue reflected values as specified in the specularColor field. The following table describes which Material fields are typically supported in popular low-end systems and suggests actions for browser implementors to take when a field is not supported.
Field Supported? Suggested Action ambientIntensity No Ignore diffuseColor Yes Use specularColor No Ignore emissiveColor No If diffuse == 0.8 0.8 0.8, use emissive shininess Yes Use transparency Yes if < 0.5 then opaque else transparent
The emissive color field is used when all other colors are black (0 0 0 ). Rendering systems which do not support specular color may nevertheless support a specular intensity. This should be derived by taking the dot product of the specified RGB specular value with the vector [.32 .57 .11]. This adjusts the color value to compensate for the variable sensitivity of the eye to colors.
Likewise, if a system supports ambient intensity but not color, the same thing should be done with the ambient color values to generate the ambient intensity. If a rendering system does not support per-object ambient values, it should set the ambient value for the entire scene at the average ambient value of all objects.
It is also expected that simpler rendering systems may be unable to support both diffuse and emissive objects in the same world. Also, many renderers will not support ambientIntensity with per-vertex colors specified with the Color node.
MovieTexture
MovieTexture {
exposedField SFBool loop FALSE
exposedField SFFloat speed 1
exposedField SFTime startTime 0
exposedField SFTime stopTime 0
exposedField MFString url []
field SFBool repeatS TRUE
field SFBool repeatT TRUE
eventOut SFFloat duration_changed
eventOut SFBool isActive
}
The MovieTexture node defines a time dependent texture map (contained in a movie file) and parameters for controlling the movie and the texture mapping. A MovieTexture can also be used as the source of sound data for a Sound node, but in this special case are not used for rendering.
Texture maps are defined in a 2D coordinate system, (s, t), that ranges from 0.0 to 1.0 in both directions. The bottom edge of the image corresponds to the S-axis of the texture map, and left edge of the image corresponds to the T-axis of the texture map. The lower-left pixel of the image corresponds to s=0, t=0, and the top-right pixel of the image corresponds to s=1, t=1.
The url field that defines the movie data must support MPEG1-Systems (audio and video) or MPEG1-Video (video-only) movie file formats [MPEG]. See "Concepts - URLS and URNs" for details on the url field. It is recommended that implementations support greyscale or alpha transparency rendering if the specific movie format being used supports these features.
See "Concepts - Lighting Model" for details on lighting equations and the interaction between textures, materials, and geometries.
As soon as the movie is loaded, a duration_changed eventOut is sent. This indicates the duration of the movie, in seconds. This eventOut value can be read (for instance, by a Script) to determine the duration of a movie. A value of -1 implies the movie has not yet loaded or the value is unavailable for some reason.
The loop, startTime, and stopTime exposedFields and the isActive eventOut, and their affects on the MovieTexture node, are discussed in detail in the "Concepts - Time Dependent Nodes" section. The "cycle" of a MovieTexture is the length of time in seconds for one playing of the movie at the specified speed.
If a MovieTexture is inactive when the movie is first loaded, then frame 0 is shown in the texture if speed is non-negative, or the last frame of the movie if speed is negative. A MovieTexture will always display frame 0 if speed = 0. For positive values of speed, the frame an active MovieTexture will display at time now corresponds to the frame at movie time (i.e., in the movie's local time system with frame 0 at time 0, at speed = 1):
fmod (now - startTime, duration/speed)
If speed is negative, then the frame to display is the frame at movie time:
duration + fmod(now - startTime, duration/speed).
When a MovieTexture becomes inactive, the frame corresponding to the time at which the MovieTexture became inactive will remain as the texture.
The speed exposedField indicates how fast the movie should be played. A speed of 2 indicates the movie plays twice as fast. Note that the duration_changed output is not affected by the speed exposedField. set_speed events are ignored while the movie is playing. A negative speed implies that the movie will play backwards. However, content creators should note that this may not work for streaming movies or very large movie files.
MovieTextures can be referenced by an Appearance node's texture field (as a movie texture) and by a Sound node's source field (as an audio source only). A legal implementation of the MovieTexture node is not required to play audio if speed is not equal to 1.
NavigationInfo
NavigationInfo {
eventIn SFBool set_bind
exposedField MFFloat avatarSize [ 0.25, 1.6, 0.75 ]
exposedField SFBool headlight TRUE
exposedField SFFloat speed 1.0
exposedField MFString type "WALK"
exposedField SFFloat visibilityLimit 0.0
eventOut SFBool isBound
}
The NavigationInfo node contains information describing the physical characteristics of the viewer and viewing model. NavigationInfo is a bindable node (see "Concepts - Bindable Children Nodes") and thus there exists a NavigationInfo stack in the browser in which the top-most NavigationInfo on the stack is the currently active NavigationInfo. The current NavigationInfo is considered to be a child of the current Viewpoint - regardless of where it is initially located in the file. Whenever the current Viewpoint changes, the current NavigationInfo must be re-parented to it. Whenever the current NavigationInfo changes, the new NavigationInfo must be re-parented to the current Viewpoint.
If a TRUE value is sent to the set_bind eventIn of a NavigationInfo, it is pushed onto the NavigationInfo stack and activated. When a NavigationInfo is bound, the browser uses the fields of the NavigationInfo to set the navigation controls of its user interface and the NavigationInfo is conceptually re-parented under the currently bound Viewpoint. All subsequent scaling changes to the current Viewpoint's coordinate system automatically change aspects (see below) of the NavigationInfo values used in the browser (e.g. scale changes to any parent transformation). A FALSE value of set_bind, pops the NavigationInfo from the stack, results in an isBound FALSE event, and pops to the next entry in the stack which must be re-parented to the current Viewpoint. See "Concepts - Bindable Children Nodes" for more details on the the binding stacks.
The type field specifies a navigation paradigm to use. Minimally, browsers shall support the following navigation types: "WALK", "EXAMINE", "FLY", and "NONE". Walk navigation is used for exploring a virtual world. It is recommended that the browser should support a notion of gravity in walk mode. Fly navigation is similar to walk except that no notion of gravity should be enforced. There should still be some notion of "up" however. Examine navigation is typically used to view individual objects and often includes (but does not require) the ability to spin the object and move it closer or further away. The "none" choice removes all navigation controls - the user navigates using only controls provided in the scene, such as guided tours. Also allowed are browser specific navigation types. These should include a unique suffix (e.g. _sgi.com) to prevent conflicts. The type field is multi-valued so that authors can specify fallbacks in case a browser does not understand a given type. If none of the types are recognized by the browser, then the default "WALK" is used. These strings values are case sensitive ("walk" is not equal to "WALK").
The speed is the rate at which the viewer travels through a scene in meters per second. Since viewers may provide mechanisms to travel faster or slower, this should be the default or average speed of the viewer. If the NavigationInfo type is EXAMINE, speed should affect panning and dollying--it should have no effect on the rotation speed. The transformation hierarchy of the currently bound Viewpoint (see above) scales the speed - translations and rotations have no effect on speed. Speed must be >= 0.0 - where 0.0 specifies a stationary avatar.
The avatarSize field specifies the user's physical dimensions in the world for the purpose of collision detection and terrain following. It is a multi-value field to allow several dimensions to be specified. The first value should be the allowable distance between the user's position and any collision geometry (as specified by Collision) before a collision is detected. The second should be the height above the terrain the viewer should be maintained. The third should be the height of the tallest object over which the viewer can "step". This allows staircases to be built with dimensions that can be ascended by all browsers. Additional values are browser dependent and all values may be ignored, but if a browser interprets these values the first 3 should be interpreted as described above. The transformation hierarchy of the currently bound Viewpoint scales the avatarSize - translations and rotations have no effect on avatarSize.
For purposes of terrain following the browser needs a notion of the down direction (down vector), since gravity is applied in the direction of the down vector. This down vector should be along the negative Y-axis in the local coordinate system of the currently bound Viewpoint (i.e., the accumulation of the Viewpoint's parent transformations, not including the Viewpoint's orientation field).
The visibilityLimit field sets the furthest distance the user is able to see. The browser may clip all objects beyond this limit, fade them into the background or ignore this field. A value of 0.0 (the default) indicates an infinite visibility limit. VisibilityLimit is restricted to be >= 0.0.
The speed, avatarSize and visibilityLimit values are all scaled by the transformation being applied to currently bound Viewpoint. If there is no currently bound Viewpoint, they are interpreted in the world coordinate system. This allows these values to be automatically adjusted when binding to a Viewpoint that has a scaling transformation applied to it without requiring a new NavigationInfo node to be bound as well. If the scale applied to the Viewpoint is non-uniform the behavior is undefined.
The headlight field specifies whether a browser should turn a headlight on. A headlight is a directional light that always points in the direction the user is looking. Setting this field to TRUE allows the browser to provide a headlight, possibly with user interface controls to turn it on and off. Scenes that enlist pre-computed lighting (e.g. radiosity solutions) can turn the headlight off. The headlight shall have intensity = 1, color = 1 1 1, ambientIntensity = 0.0, and direction = 0 0 -1.
It is recommended that the near clipping plane should be set to one-half of the collision radius as specified in the avatarSize field. This recommendation may be ignored by the browser, but setting the near plane to this value prevents excessive clipping of objects just above the collision volume and provides a region inside the collision volume for content authors to include geometry that should remain fixed relative to the viewer, such as icons or a heads-up display, but that should not be occluded by geometry outside of the collision volume.
The first NavigationInfo node found during reading of the world is automatically bound (receives a set_bind TRUE event) and supplies the initial navigation parameters.
Normal
Normal {
exposedField MFVec3f vector []
}
This node defines a set of 3D surface normal vectors to be used in the vector field of some geometry nodes (IndexedFaceSet, ElevationGrid). This node contains one multiple-valued field that contains the normal vectors. Normals should be unit-length or results are undefined.
To save network bandwidth, it is expected that implementations will be able to automatically generate appropriate normals if none are given. However, the results will vary from implementation to implementation.
NormalInterpolator
NormalInterpolator {
eventIn SFFloat set_fraction
exposedField MFFloat key []
exposedField MFVec3f keyValue []
eventOut MFVec3f value_changed
}
This node interpolates among a set of multi-valued Vec3f values, suitable for transforming normal vectors. All output vectors will have been normalized by the interpolator.
The number of normals in the keyValue field must be an integer multiple of the number of keyframes in the key field; that integer multiple defines how many normals will be contained in the value_changed events.
Normal interpolation is to be performed on the surface of the unit sphere. That is, the output values for a linear interpolation from a point P on the unit sphere to a point Q also on unit sphere should lie along the shortest arc (on the unit sphere) connecting points P and Q. Also, equally spaced input fractions will result in arcs of equal length. Cases where P and Q are diagonally opposing allow an infinite number of arcs. The interpolation for this case can be along any one of these arcs.
Refer to "Concepts - Interpolators" for a more detailed discussion of interpolators.
OrientationInterpolator
OrientationInterpolator {
eventIn SFFloat set_fraction
exposedField MFFloat key []
exposedField MFRotation keyValue []
eventOut SFRotation value_changed
}
This node interpolates among a set of SFRotation values. The rotations are absolute in object space and are, therefore, not cumulative. The keyValue field must contain exactly as many rotations as there are keyframes in the key field, or an error will be generated and results will be undefined.
An orientation represents the final position of an object after a rotation has been applied. An OrientationInterpolator will interpolate between two orientations by computing the shortest path on the unit sphere between the two orientations. The interpolation will be linear in arc length along this path. The path between two diagonally opposed orientations will be any one of the infinite possible paths with arc length PI.
If two consecutive keyValue values exist such that the arc length between them is greater than PI, then the interpolation will take place on the arc complement. For example, the interpolation between the orientations:
0 1 0 0 --> 0 1 0 5.0
is equivalent to the rotation between the two orientations:
0 1 0 2*PI --> 0 1 0 5.0
Refer to "Concepts - Interpolators" for a more detailed discussion of interpolators.
PixelTexture
PixelTexture {
exposedField SFImage image 0 0 0
field SFBool repeatS TRUE
field SFBool repeatT TRUE
}
The PixelTexture node defines a 2D image-based texture map as an explicit array of pixel values and parameters controlling tiling repetition of the texture onto geometry.
Texture maps are defined in a 2D coordinate system, (s, t), that ranges from 0.0 to 1.0 in both directions. The bottom edge of the pixel image corresponds to the S-axis of the texture map, and left edge of the pixel image corresponds to the T-axis of the texture map. The lower-left pixel of the pixel image corresponds to s=0, t=0, and the top-right pixel of the image corresponds to s=1, t=1.
Images may be one component (greyscale), two component (greyscale plus alpha opacity), three component (full RGB color), or four-component (full RGB color plus alpha opacity). An ideal VRML implementation will use the texture image to modify the diffuse color and transparency ( = 1 - alpha opacity) of an object's material (specified in a Material node), then perform any lighting calculations using the rest of the object's material properties with the modified diffuse color to produce the final image. The texture image modifies the diffuse color and transparency depending on how many components are in the image, as follows:
Browsers may approximate this ideal behavior to increase performance. One common optimization is to calculate lighting only at each vertex and combining the texture image with the color computed from lighting (performing the texturing after lighting). Another common optimization is to perform no lighting calculations at all when texturing is enabled, displaying only the colors of the texture image.
See "Concepts - Lighting Model" for details on the VRML lighting equations.
See the "Field Reference - SFImage" specification for details on how to specify an image.
The repeatS and repeatT fields specify how the texture wraps in the S and T directions. If repeatS is TRUE (the default), the texture map is repeated outside the 0-to-1 texture coordinate range in the S direction so that it fills the shape. If repeatS is FALSE, the texture coordinates are clamped in the S direction to lie within the 0-to-1 range. The repeatT field is analogous to the repeatS field.
PlaneSensor
PlaneSensor {
exposedField SFBool autoOffset TRUE
exposedField SFBool enabled TRUE
exposedField SFVec2f maxPosition -1 -1
exposedField SFVec2f minPosition 0 0
exposedField SFVec3f offset 0 0 0
eventOut SFBool isActive
eventOut SFVec3f trackPoint_changed
eventOut SFVec3f translation_changed
}
The PlaneSensor maps pointing device (e.g. mouse or wand) motion into translation in two dimensions, in the XY plane of its local space. PlaneSensor uses the descendant geometry of its parent node to determine if a hit occurs.
The enabled exposed field enables and disables the PlaneSensor - if TRUE, the sensor reacts appropriately to user events, if FALSE, the sensor does not track user input or send output events. If enabled receives a FALSE event and isActive is TRUE, the sensor becomes disabled and deactivated, and outputs an isActive FALSE event. If enabled receives a TRUE event the sensor is enabled and ready for user activation.
The PlaneSensor generates events if the pointing device is activated while over any descendant geometry nodes of its parent group and then moved while activated. Typically, the pointing device is a 2D device such as a mouse. The pointing device is considered to be moving within a plane at a fixed distance from the viewer and perpendicular to the line of sight; this establishes a set of 3D coordinates for the pointer. If a 3D pointer is in use, then the sensor generates events only when the pointer is within the user's field of view. In either case, the pointing device is considered to "pass over" geometry when that geometry is intersected by a line extending from the viewer and passing through the pointer's 3D coordinates. If multiple sensors' geometry intersect this line (hereafter called the bearing), only the nearest will be eligible to generate events.
Upon activation of the pointing device (e.g. mouse button down) over the sensor's geometry, an isActive TRUE event is sent. Dragging motion is mapped into a relative translation in the XY plane of the sensor's local coordinate system as it was defined at the time of activation. For each subsequent position of the bearing, a translation_changed event is output which corresponds to a relative translation from the original intersection point projected onto the XY plane, plus the offset value. The sign of the translation is defined by the XY plane of the sensor's coordinate system. trackPoint_changed events reflect the unclamped drag position on the surface of this plane. When the pointing device is deactivated and autoOffset is TRUE, offset is set to the last translation value and an offset_changed event is generated. See "Concepts - Drag Sensors" for more det