NAME¶
glMaterial - 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 ALSO¶
glColorMaterial(), glLight(),
glLightModel()