glMaterial — specify material parameters for the lighting model
void fsfuncglMaterialf( | GLenum face, |
| GLenum pname, | |
GLfloat param); |
void fsfuncglMaterialx( | GLenum face, |
| GLenum pname, | |
GLfixed param); |
face
Specifies which face or faces are being updated. Must be
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 fsfuncglMaterialfv( | GLenum face, |
| GLenum pname, | |
const GLfloat * params); |
void fsfuncglMaterialxv( | GLenum face, |
| GLenum pname, | |
const GLfixed * params); |
face
Specifies which face or faces are being updated.
Must be 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, or
GL_AMBIENT_AND_DIFFUSE.
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, 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,
must be GL_FRONT_AND_BACK and specifies that both
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 fixed-point or floating-point values that
specify the ambient RGBA reflectance of the material.
The values are not clamped. The initial ambient
reflectance is
(0.2, 0.2, 0.2, 1.0).
GL_DIFFUSE
params
contains four fixed-point or floating-point values that
specify the diffuse RGBA reflectance of the material.
The values are not clamped. The initial diffuse
reflectance is
(0.8, 0.8, 0.8, 1.0).
GL_SPECULAR
params
contains four fixed-point or floating-point values that
specify the specular RGBA reflectance of the material.
The values are not clamped. The initial specular
reflectance is
(0, 0, 0, 1).
GL_EMISSION
params
contains four fixed-point or floating-point values that
specify the RGBA emitted light intensity of the material.
The values are not clamped. The initial emission
intensity is
(0, 0, 0, 1).
GL_SHININESS
params
is a single fixed-point or floating-point value that
specifies the RGBA specular exponent of the material.
Only values in the range [0, 128] are accepted. The
initial specular exponent is 0.
GL_AMBIENT_AND_DIFFUSE
Equivalent to calling glMaterial
twice with the same parameter values, once with
GL_AMBIENT
and once with GL_DIFFUSE.
To change the diffuse and ambient material per vertex,
color material can be used.
To enable and disable
GL_COLOR_MATERIAL, call
glEnable and
glDisable with
argument GL_COLOR_MATERIAL.
Color material is initially disabled.
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 [0, 128]
is specified.
Copyright © 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.