glMaterial, glMaterialf, glMateriali, glMaterialfv, glMaterialiv
- specify material parameters for the lighting
model
void glMaterialf(
GLenum face,
GLenum pname,
GLfloat param ); void glMateriali(
GLenum face,
GLenum pname,
GLint param );
Specifies which face or faces are being updated. Must be
one of GL_FRONT, GL_BACK, or GL_FRONT_AND_BACK. Specifies
the single-valued material parameter of the face or faces
that is being updated. Must be GL_SHININESS. Specifies
the value that parameter GL_SHININESS will be set to.
void glMaterialfv(
GLenum face,
GLenum pname,
const GLfloat *params ); void glMaterialiv(
GLenum face,
GLenum pname,
const GLint *params );
Specifies which face or faces are being updated. Must be
one of GL_FRONT, GL_BACK, or GL_FRONT_AND_BACK. 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. Specifies a pointer to the value or
values that pname will be set to.
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: 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. Floatingpoint
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). 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). 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). 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 floatingpoint
values are clamped. The initial emission intensity
for both front- and back-facing materials is (0, 0, 0, 1).
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. Equivalent to calling glMaterial() twice with
the same parameter values, once with GL_AMBIENT and once
with GL_DIFFUSE. 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.
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.
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.
glGetMaterial()
glColorMaterial(3), glLight(3), glLightModel(3)
glMaterial(3G)
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