GLMATERIAL(3G)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-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 ALSOglColorMaterial(3G), glLight(3G), glLightModel(3G)
March 1, 2011