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 calcula-tions. calculations.
tions.
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, speci-fies specifies
fies 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 repre-sentable representable
sentable 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 repre-sentable representable
sentable 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 repre-sentable representable
sentable 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 emit-ted emitted
ted 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 specu-lar specular
lar 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(3G), glLight(3G), glLightModel(3G)
GLMATERIAL(3G)
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