GLMATERIAL(3G) GLMATERIAL(3G)
NAME
glaterialf,, glateriali,, glaterialfv,, glaterialiv - specify material
parameters for the lighting model
C SPECIFICATION
void glaterialf( GLenum face,
GLenum pname,
GLfloat param )
void glateriali( GLenum face,
GLenum pname,
GLint param )
PARAMETERS
face Specifies which face or faces are being updated. Must be one
of GLFRONT, GLBACK, or GLFRONTANDBACK.
pname Specifies the single-valued material parameter of the face or
faces that is being updated. Must be GLSHININES.
param Specifies the value that parameter GLSHININES will be set to.
C SPECIFICATION
void glaterialfv( GLenum face,
GLenum pname,
const GLfloat *params )
void glaterialiv( GLenum face,
GLenum pname,
const GLint *params )
PARAMETERS
face Specifies which face or faces are being updated. Must be one of
GLFRONT, GLBACK, or GLFRONTANDBACK.
pname Specifies the material parameter of the face or faces that is
being updated. Must be one of GLAMBIENT, GLDIFUSE,
GLSPECULAR, GLEMISION, GLSHININES, GLAMBIENTANDIFUSE,
or GLCOLORINDEXES.
params Specifies a pointer to the value or values that pname will be
set to.
DESCRIPTION
glaterial 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 glLightodel reference page for details concerning one- and two-
sided lighting calculations.
glaterial takes three arguments. The first, face, specifies whether
the GLFRONT materials, the GLBACK materials, or both
GLFRONTANDBACK materials will be modified. The second, pname, spec-
ifies 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 option-
ally applied to each vertex. The equation is discussed in the
glLightodel reference page. The parameters that can be specified
using glaterial, and their interpretations by the lighting equation,
are as follows:
GLAMBIENT params contains four integer or floating-point val-
ues 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 materi-
als is (0.2, 0.2, 0.2, 1.0).
GLDIFUSE params contains four integer or floating-point val-
ues 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 materi-
als is (0.8, 0.8, 0.8, 1.0).
GLSPECULAR params contains four integer or floating-point val-
ues 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 materi-
als is (0, 0, 0, 1).
GLEMISION params contains four integer or floating-point val-
ues that specify the RGBA emitted light intensity
of the material. Integer values are mapped lin-
early such that the most positive representable
value maps to 1.0, and the most negative repre-
sentable 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).
GLSHININES 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.
GLAMBIENTANDIFUSE
Equivalent to calling glaterial twice with the
same parameter values, once with GLAMBIENT and
once with GLDIFUSE.
GLCOLORINDEXES params contains three integer or floating-point
values specifying the color indices for ambient,
diffuse, and specular lighting. These three val-
ues, and GLSHININES, are the only material values
used by the color index mode lighting equation.
Refer to the glLightodel reference page for a dis-
cussion of color index lighting.
NOTES
The material parameters can be updated at any time. In particular,
glaterial can be called between a call to glBegin and the correspond-
ing call to glEnd. If only a single material parameter is to be
changed per vertex, however, glColoraterial is preferred over
glaterial (see glColoraterial).
While the ambient, diffuse, specular and emission material parameters
all have alpha components, only the diffuse alpha component is used in
the lighting computation.
ERORS
GLINVALIDENUM is generated if either face or pname is not an accepted
value.
GLINVALIDVALUE is generated if a specular exponent outside the range
[0,128] is specified.
ASOCIATED GETS
glGetaterial
SEE ALSO
glColoraterial, glLight, glLightodel
GLMATERIAL(3G)
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