xenocara/doc/gl-docs/GL/gl/material.3gl

'\" e
'\"! eqn | mmdoc
'\"macro stdmacro
.ds Vn Version 1.2
.ds Dt 24 September 1999
.ds Re Release 1.2.1
.ds Dp Jan 14 18:30
.ds Dm 01 material.
.ds Xs 18013 8 material.gl
.TH GLMATERIAL 3G
.SH NAME
.B "glMaterialf, glMateriali, glMaterialfv, glMaterialiv
\- specify material parameters for the lighting model

.SH C SPECIFICATION
void \f3glMaterialf\fP(
GLenum \fIface\fP,
.nf
.ta \w'\f3void \fPglMaterialf( 'u
	GLenum \fIpname\fP,
	GLfloat \fIparam\fP )
.fi
void \f3glMateriali\fP(
GLenum \fIface\fP,
.nf
.ta \w'\f3void \fPglMateriali( 'u
	GLenum \fIpname\fP,
	GLint \fIparam\fP )
.fi

.SH PARAMETERS
.TP \w'\fIparams\fP\ \ 'u 
\f2face\fP
Specifies which face or faces are being updated.
Must be one of
\%\f3GL_FRONT\fP,
\%\f3GL_BACK\fP, or
\%\f3GL_FRONT_AND_BACK\fP.
.TP
\f2pname\fP
Specifies the single-valued material parameter of the face or faces
that is being updated.
Must be \%\f3GL_SHININESS\fP.
.TP
\f2param\fP
Specifies the value that parameter \%\f3GL_SHININESS\fP will be set to.
.SH C SPECIFICATION
void \f3glMaterialfv\fP(
GLenum \fIface\fP,
.nf
.ta \w'\f3void \fPglMaterialfv( 'u
	GLenum \fIpname\fP,
	const GLfloat \fI*params\fP )
.fi
void \f3glMaterialiv\fP(
GLenum \fIface\fP,
.nf
.ta \w'\f3void \fPglMaterialiv( 'u
	GLenum \fIpname\fP,
	const GLint \fI*params\fP )
.fi

.SH PARAMETERS
.TP
\f2face\fP
Specifies which face or faces are being updated.
Must be one of
\%\f3GL_FRONT\fP,
\%\f3GL_BACK\fP, or
\%\f3GL_FRONT_AND_BACK\fP.
.TP
\f2pname\fP
Specifies the material parameter of the face or faces that is being updated.
Must be one of
\%\f3GL_AMBIENT\fP,
\%\f3GL_DIFFUSE\fP,
\%\f3GL_SPECULAR\fP,
\%\f3GL_EMISSION\fP,
\%\f3GL_SHININESS\fP,
\%\f3GL_AMBIENT_AND_DIFFUSE\fP,  or
\%\f3GL_COLOR_INDEXES\fP.
.TP
\f2params\fP
Specifies a pointer to the value or values that \f2pname\fP will be set to.
.SH DESCRIPTION
\%\f3glMaterial\fP 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 \%\f3glLightModel\fP reference page for details concerning one- and
two-sided lighting calculations.
.P
\%\f3glMaterial\fP takes three arguments.
The first,
\f2face\fP,
specifies whether the
\%\f3GL_FRONT\fP materials, the
\%\f3GL_BACK\fP materials, or both
\%\f3GL_FRONT_AND_BACK\fP materials will be modified.
The second,
\f2pname\fP,
specifies which of several parameters in one or both sets will be modified.
The third,
\f2params\fP,
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 \%\f3glLightModel\fP reference page.
The parameters that can be specified using \%\f3glMaterial\fP,
and their interpretations by the lighting equation, are as follows:
.TP 20
\%\f3GL_AMBIENT\fP
\f2params\fP 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
\%\f3GL_DIFFUSE\fP
\f2params\fP 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
\%\f3GL_SPECULAR\fP
\f2params\fP 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
\%\f3GL_EMISSION\fP
\f2params\fP 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
\%\f3GL_SHININESS\fP
\f2params\fP 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
\%\f3GL_AMBIENT_AND_DIFFUSE\fP
Equivalent to calling \%\f3glMaterial\fP twice with the same parameter values,
once with \%\f3GL_AMBIENT\fP and once with \%\f3GL_DIFFUSE\fP.
.TP
\%\f3GL_COLOR_INDEXES\fP
\f2params\fP contains three integer or floating-point values specifying
the color indices for ambient,
diffuse,
and specular lighting.
These three values,
and \%\f3GL_SHININESS\fP,
are the only material values used by the color index mode lighting equation.
Refer to the \%\f3glLightModel\fP reference page for a discussion 
of color index lighting.
.SH NOTES
The material parameters can be updated at any time.
In particular,
\%\f3glMaterial\fP can be called between a call to \%\f3glBegin\fP and the corresponding
call to \%\f3glEnd\fP.
If only a single material parameter is to be changed per vertex,
however,
\%\f3glColorMaterial\fP is preferred over \%\f3glMaterial\fP
(see \%\f3glColorMaterial\fP).
.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
\%\f3GL_INVALID_ENUM\fP is generated if either \f2face\fP or \f2pname\fP is not
an accepted value.
.P
\%\f3GL_INVALID_VALUE\fP is generated if a specular exponent outside the range
[0,128] is specified.
.SH ASSOCIATED GETS
\%\f3glGetMaterial\fP
.SH SEE ALSO
\%\f3glColorMaterial(3G)\fP,
\%\f3glLight(3G)\fP,
\%\f3glLightModel(3G)\fP