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glMaterial(3G)
NAME
glMaterial, glMaterialf, glMateriali, glMaterialfv, glMaterialiv - specify
material parameters for the lighting model
SYNOPSIS
void glMaterialf(
GLenum face,
GLenum pname,
GLfloat param );
void glMateriali(
GLenum face,
GLenum pname,
GLint param );
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.
SYNOPSIS
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 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.
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 initial 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 initial 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 initial specular reflectance for both front- and
back-facing materials is (0, 0, 0, 1).
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 initial emission intensity for both front- and back-
facing materials is (0, 0, 0, 1).
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 initial 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()).
While the ambient, diffuse, specular and emission material parameters all
have alpha components, only the diffuse alpha component is used in the
lighting computation.
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(3), glLight(3), glLightModel(3)
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Index for
Section 3G |
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Alphabetical
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