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glMaterial — specify material parameters for the lighting model
void glMaterialf( | GLenum | face, |
| GLenum | pname, | |
| GLfloat | param); |
void glMateriali( | GLenum | face, |
| GLenum | pname, | |
| GLint | param); |
face
Specifies which face or faces are being updated.
Must be one of
GL_FRONT,
GL_BACK, or
GL_FRONT_AND_BACK.
pname
Specifies the single-valued material parameter of the face or faces
that is being updated.
Must be GL_SHININESS.
param
Specifies the value that parameter GL_SHININESS will be set to.
void glMaterialfv( | GLenum | face, |
| GLenum | pname, | |
| const GLfloat * | params); |
void glMaterialiv( | GLenum | face, |
| GLenum | pname, | |
| const GLint * | params); |
face
Specifies which face or faces are being updated.
Must be one of
GL_FRONT,
GL_BACK, or
GL_FRONT_AND_BACK.
pname
Specifies the material parameter of the face or faces that is being updated.
Must be one of
GL_AMBIENT,
GL_DIFFUSE,
GL_SPECULAR,
GL_EMISSION,
GL_SHININESS,
GL_AMBIENT_AND_DIFFUSE, or
GL_COLOR_INDEXES.
params
Specifies a pointer to the value or values that pname will be set to.
glMaterial assigns values to material parameters.
There are two matched sets of material parameters.
One,
the front-facing set,
is used to shade points,
lines,
bitmaps,
and all polygons
(when two-sided lighting is disabled),
or just front-facing polygons
(when two-sided lighting is enabled).
The other set,
back-facing,
is used to shade back-facing polygons only when two-sided lighting is enabled.
Refer to the glLightModel reference page for details concerning one- and
two-sided lighting calculations.
glMaterial takes three arguments.
The first,
face,
specifies whether the
GL_FRONT materials, the
GL_BACK materials, or both
GL_FRONT_AND_BACK materials will be modified.
The second,
pname,
specifies which of several parameters in one or both sets will be modified.
The third,
params,
specifies what value or values will be assigned to the specified parameter.
Material parameters are used in the lighting equation that is optionally
applied to each vertex.
The equation is discussed in the glLightModel reference page.
The parameters that can be specified using glMaterial,
and their interpretations by the lighting equation, are as follows:
GL_AMBIENT
params contains four integer or floating-point values that specify
the ambient RGBA reflectance of the material.
Integer values are mapped linearly such that the most positive representable
value maps to 1.0,
and the most negative representable value maps to
GL_DIFFUSE
params contains four integer or floating-point values that specify
the diffuse RGBA reflectance of the material.
Integer values are mapped linearly such that the most positive representable
value maps to 1.0,
and the most negative representable value maps to
GL_SPECULAR
params contains four integer or floating-point values that specify
the specular RGBA reflectance of the material.
Integer values are mapped linearly such that the most positive representable
value maps to 1.0,
and the most negative representable value maps to
GL_EMISSION
params contains four integer or floating-point values that specify
the RGBA emitted light intensity of the material.
Integer values are mapped linearly such that the most positive representable
value maps to 1.0,
and the most negative representable value maps to
GL_SHININESS
params is a single integer or floating-point value that specifies
the RGBA specular exponent of the material.
Integer and floating-point values are mapped directly.
Only values in the range
GL_AMBIENT_AND_DIFFUSE
Equivalent to calling glMaterial twice with the same parameter values,
once with GL_AMBIENT and once with GL_DIFFUSE.
GL_COLOR_INDEXES
params contains three integer or floating-point values specifying
the color indices for ambient,
diffuse,
and specular lighting.
These three values,
and GL_SHININESS,
are the only material values used by the color index mode lighting equation.
Refer to the glLightModel reference page for a discussion
of color index lighting.
The material parameters can be updated at any time.
In particular,
glMaterial can be called between a call to glBegin and the corresponding
call to glEnd.
If only a single material parameter is to be changed per vertex,
however,
glColorMaterial is preferred over glMaterial
(see glColorMaterial).
While the ambient, diffuse, specular and emission material parameters all have alpha components, only the diffuse alpha component is used in the lighting computation.
GL_INVALID_ENUM is generated if either face or pname is not
an accepted value.
GL_INVALID_VALUE is generated if a specular exponent outside the range
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.