glMaterial(3G) OpenGL Reference glMaterial(3G)
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 )
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.
void glMaterialfv( GLenum face,
GLenum pname,
const GLfloat *params )
void glMaterialiv( GLenum face,
GLenum pname,
const GLint *params )
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.
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
Page 1
glMaterial(3G) OpenGL Reference glMaterial(3G)
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
Page 2
glMaterial(3G) OpenGL Reference glMaterial(3G)
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 [Toc] [Back]
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.
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, glLight, glLightModel
PPPPaaaaggggeeee 3333 [ Back ]
|
