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_C_ Original Code. The Original Code is: OpenGL Sample Implementation,
_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
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_C_ established by SGI in conjunction with the Original Code are The
_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
_C_ Window System(R) (Version 1.3), released October 19, 1998. This software
_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation
_C_ published by SGI, but has not been independently verified as being
_C_ compliant with the OpenGL(R) version 1.2.1 Specification.
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_C_ $Date$ $Revision$
_C_ The first character in this file must be an '_'!
_C_ Anything on a line after _C_ is ignored
_define(_filters,eqn)_C_
_C_      eqn is automatically replaced with neqn for nroff
_header(Material,specify material parameters for the lighting model)
_names(Material,[fi])
.SH PARAMETERS
_phead(_param1)
Specifies which face or faces are being updated.
Must be one of
_const(FRONT),
_const(BACK), or
_const(FRONT_AND_BACK).
_phead(_param2)
Specifies the single-valued material parameter of the face or faces
that is being updated.
Must be _const(SHININESS).
_phead(_param3)
Specifies the value that parameter _const(SHININESS) will be set to.
_names(Material,[fi]v)
.SH PARAMETERS
_phead(_param1)
Specifies which face or faces are being updated.
Must be one of
_const(FRONT),
_const(BACK), or
_const(FRONT_AND_BACK).
_phead(_param2)
Specifies the material parameter of the face or faces that is being updated.
Must be one of
_const(AMBIENT),
_const(DIFFUSE),
_const(SPECULAR),
_const(EMISSION),
_const(SHININESS),
_const(AMBIENT_AND_DIFFUSE),  or
_const(COLOR_INDEXES).
_phead(_param3)
Specifies a pointer to the value or values that _param2 will be set to.
.SH DESCRIPTION
_cmnd assigns values to material parameters.
There are two matched sets of material parameters.
One,
the \f2front-facing\fP 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,
\f2back-facing\fP,
is used to shade back-facing polygons only when two-sided lighting is enabled.
Refer to the _cmnd(LightModel) reference page for details concerning one- and
two-sided lighting calculations.
.P
_cmnd takes three arguments.
The first,
_param1,
specifies whether the
_const(FRONT) materials, the
_const(BACK) materials, or both
_const(FRONT_AND_BACK) materials will be modified.
The second,
_param2,
specifies which of several parameters in one or both sets will be modified.
The third,
_param3,
specifies what value or values will be assigned to the specified parameter.
.P
Material parameters are used in the lighting equation that is optionally
applied to each vertex.
The equation is discussed in the _cmnd(LightModel) reference page.
The parameters that can be specified using _cmnd,
and their interpretations by the lighting equation, are as follows:
.TP 20
_const(AMBIENT)
_param3 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).
.TP
_const(DIFFUSE)
_param3 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).
.TP
_const(SPECULAR)
_param3 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).
.TP
_const(EMISSION)
_param3 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).
.TP
_const(SHININESS)
_param3 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.
.TP
_const(AMBIENT_AND_DIFFUSE)
Equivalent to calling _cmnd twice with the same parameter values,
once with _const(AMBIENT) and once with _const(DIFFUSE).
.TP
_const(COLOR_INDEXES)
_param3 contains three integer or floating-point values specifying
the color indices for ambient,
diffuse,
and specular lighting.
These three values,
and _const(SHININESS),
are the only material values used by the color index mode lighting equation.
Refer to the _cmnd(LightModel) reference page for a discussion 
of color index lighting.
.SH NOTES
The material parameters can be updated at any time.
In particular,
_cmnd can be called between a call to _cmnd(Begin) and the corresponding
call to _cmnd(End).
If only a single material parameter is to be changed per vertex,
however,
_cmnd(ColorMaterial) is preferred over _cmnd
(see _cmnd(ColorMaterial)).
.P
While the ambient, diffuse, specular and emission material parameters
all have alpha components, only the diffuse alpha component is used in
the lighting computation.
.SH ERRORS
_const(INVALID_ENUM) is generated if either _param1 or _param2 is not
an accepted value.
.P
_const(INVALID_VALUE) is generated if a specular exponent outside the range
[0,128] is specified.
.SH ASSOCIATED GETS
_cmnd(GetMaterial)
.SH SEE ALSO
_cmnd(ColorMaterial),
_cmnd(Light),
_cmnd(LightModel)
