glMaterial
NAME
glMaterialf, glMateriali, glMaterialfv,
glMaterialiv -- specify material parameters for the
lighting model
C SPECIFICATION
void glMaterialf(GLenum face,
GLenum pname,
GLfloat para)
void glMateriali(GLenum face,
GLenum pname,
GLint para)
PARAMETERS
- 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.
C SPECIFICATION
void glMaterialfv(GLenum face,
GLenum pname,
const GLfloat *params)
void glMaterialiv(GLenum face,
GLenum pname,
const GLint *params)
PARAMETERS
- 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 one of GL_AMBIENT,
GL_DIFFUSE, GL_SPECULAR, GL_EMISSION,
GL_SHININESS, GL_AMBIENT_AND_DIFFUSE, or
GL_COLOR_INDEXES.
- param
-
Specifies a pointer to the value or values that pname will be
set to.
DESCRIPTION
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 -1.0.
Floating-point values are mapped directly. Neither integer nor
floating-point values are clamped. The default ambient reflectance
for both front- and back-facing materials is (0.2, 0.2, 0.2, 1.0).
- 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 -1.0.
Floating-point values are mapped directly. Neither integer nor
floating-point values are clamped. The default diffuse reflectance for
both front- and back-facing materials is (0.8, 0.8, 0.8, 1.0).
- 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 -1.0.
Floating-point values are mapped directly. Neither integer nor
floating-point values are clamped. The default specular reflectance
for both front- and back-facing materials is (0.0, 0.0, 0.0, 1.0).
- 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 -1.0. Floating-point values are mapped directly. Neither integer
nor floating-point values are clamped. The default emission intensity
for both front- and back-facing materials is (0.0, 0.0, 0.0, 1.0).
- 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
[0, 128] are accepted. The default specular exponent for both
front- and back-facing materials 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.
- 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.
NOTES
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).
ERRORS
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.
ASSOCIATED GETS
glGetMaterial
SEE ALSO
glColorMaterial,
glLight,
glLightModel
back to the OpenGL index page
© 1995 Uwe Behrens. All rights reserved.