GLMATERIAL(3G) UNIX Programmer's Manual GLMATERIAL(3G)
NAME
glMaterialf, glMateriali, glMaterialfv, glMaterialiv -
specify material parameters for the lighting model
C SPECIFICATION
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.
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 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-
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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 dis-
cussed in the glLightModel reference page. The parameters
that can be specified using glMaterial, and their interpre-
tations 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
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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 dis-
cussion of color index lighting.
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NOTES
The material parameters can be updated at any time. In par-
ticular, 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(3G), glLight(3G), glLightModel(3G)
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