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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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<refentry id="glEnable">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glEnable</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glEnable</refname>
<refpurpose>enable or disable server-side GL capabilities</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glEnable</function></funcdef>
<paramdef>GLenum <parameter>cap</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>cap</parameter></term>
<listitem>
<para>
Specifies a symbolic constant indicating a GL capability.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glDisable</function></funcdef>
<paramdef>GLenum <parameter>cap</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters2"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>cap</parameter></term>
<listitem>
<para>
Specifies a symbolic constant indicating a GL capability.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glEnable</function> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> enable and disable various capabilities.
Use <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> to determine the current setting
of any capability. The initial value for each capability with the
exception of <constant>GL_DITHER</constant> and <constant>GL_MULTISAMPLE</constant> is <constant>GL_FALSE</constant>. The initial value for
<constant>GL_DITHER</constant> and <constant>GL_MULTISAMPLE</constant> is <constant>GL_TRUE</constant>.
</para>
<para>
Both <function>glEnable</function> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> take a single argument, <parameter>cap</parameter>,
which can assume one of the following values:
</para>
<variablelist>
<varlistentry>
<term><constant>GL_ALPHA_TEST</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
do alpha testing. See
<citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_AUTO_NORMAL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
generate normal vectors when either
<constant>GL_MAP2_VERTEX_3</constant> or
<constant>GL_MAP2_VERTEX_4</constant> is used to generate vertices.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_BLEND</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
blend the computed fragment color values with the values in the color
buffers. See <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_CLIP_PLANE</constant><emphasis>i</emphasis></term>
<listitem>
<para>
</para>
<para>
If enabled,
clip geometry against user-defined clipping plane <emphasis>i</emphasis>.
See <citerefentry><refentrytitle>glClipPlane</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_COLOR_LOGIC_OP</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
apply the currently selected logical operation to the computed fragment
color and color buffer values. See <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_COLOR_MATERIAL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
have one or more material parameters track the current color.
See <citerefentry><refentrytitle>glColorMaterial</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_COLOR_SUM</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
add the secondary color value to the computed fragment color.
See <citerefentry><refentrytitle>glSecondaryColor</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_COLOR_TABLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
perform a color table lookup on the incoming RGBA color values.
See <citerefentry><refentrytitle>glColorTable</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_CONVOLUTION_1D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
perform a 1D convolution operation on incoming RGBA color values.
See <citerefentry><refentrytitle>glConvolutionFilter1D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_CONVOLUTION_2D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
perform a 2D convolution operation on incoming RGBA color values.
See <citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_CULL_FACE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
cull polygons based on their winding in window coordinates.
See <citerefentry><refentrytitle>glCullFace</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_DEPTH_TEST</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
do depth comparisons and update the depth buffer. Note that even if
the depth buffer exists and the depth mask is non-zero, the
depth buffer is not updated if the depth test is disabled. See
<citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry> and
<citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_DITHER</constant> </term>
<listitem>
<para>
</para>
<para>
If enabled,
dither color components or indices before they are written to the
color buffer.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_FOG</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
blend a fog color into the post-texturing color.
See <citerefentry><refentrytitle>glFog</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_HISTOGRAM</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
histogram incoming RGBA color values.
See <citerefentry><refentrytitle>glHistogram</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_INDEX_LOGIC_OP</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
apply the currently selected logical operation to the incoming index and color
buffer indices.
See <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_LIGHT</constant><emphasis>i</emphasis></term>
<listitem>
<para>
</para>
<para>
If enabled,
include light <emphasis>i</emphasis> in the evaluation of the lighting
equation. See <citerefentry><refentrytitle>glLightModel</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_LIGHTING</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
use the current lighting parameters to compute the vertex color or index.
Otherwise, simply associate the current color or index with each
vertex. See
<citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glLightModel</refentrytitle></citerefentry>, and <citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_LINE_SMOOTH</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
draw lines with correct filtering.
Otherwise,
draw aliased lines.
See <citerefentry><refentrytitle>glLineWidth</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_LINE_STIPPLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
use the current line stipple pattern when drawing lines. See
<citerefentry><refentrytitle>glLineStipple</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_COLOR_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate RGBA values.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_INDEX</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate color indices.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_NORMAL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate normals.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_TEXTURE_COORD_1</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>
texture coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_TEXTURE_COORD_2</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
<emphasis>s</emphasis> and
<emphasis>t</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_TEXTURE_COORD_3</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>,
<emphasis>t</emphasis>, and
<emphasis>r</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_TEXTURE_COORD_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>,
<emphasis>t</emphasis>,
<emphasis>r</emphasis>, and
<emphasis>q</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_VERTEX_3</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
<emphasis>x</emphasis>, <emphasis>y</emphasis>, and <emphasis>z</emphasis> vertex coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP1_VERTEX_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh1</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint1</refentrytitle></citerefentry> generate
homogeneous
<emphasis>x</emphasis>,
<emphasis>y</emphasis>,
<emphasis>z</emphasis>, and
<emphasis>w</emphasis> vertex coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_COLOR_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate RGBA values.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_INDEX</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate color indices.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_NORMAL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate normals.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_TEXTURE_COORD_1</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>
texture coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_TEXTURE_COORD_2</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
<emphasis>s</emphasis> and
<emphasis>t</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_TEXTURE_COORD_3</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>,
<emphasis>t</emphasis>, and
<emphasis>r</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_TEXTURE_COORD_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
<emphasis>s</emphasis>,
<emphasis>t</emphasis>,
<emphasis>r</emphasis>, and
<emphasis>q</emphasis> texture coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_VERTEX_3</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
<emphasis>x</emphasis>, <emphasis>y</emphasis>, and <emphasis>z</emphasis> vertex coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MAP2_VERTEX_4</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calls to
<citerefentry><refentrytitle>glEvalCoord2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh2</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glEvalPoint2</refentrytitle></citerefentry> generate
homogeneous
<emphasis>x</emphasis>,
<emphasis>y</emphasis>,
<emphasis>z</emphasis>, and
<emphasis>w</emphasis> vertex coordinates.
See <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MINMAX</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
compute the minimum and maximum values of incoming RGBA color values.
See <citerefentry><refentrytitle>glMinmax</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_MULTISAMPLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
use multiple fragment samples in computing the final color of a pixel.
See <citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_NORMALIZE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
normal vectors are normalized to unit length
after transformation and before lighting. This method is generally
less efficient than <constant>GL_RESCALE_NORMAL</constant>. See
<citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry> and
<citerefentry><refentrytitle>glNormalPointer</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POINT_SMOOTH</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
draw points with proper filtering.
Otherwise,
draw aliased points.
See <citerefentry><refentrytitle>glPointSize</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POINT_SPRITE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
calculate texture coordinates for points based on texture
environment and point parameter settings. Otherwise texture coordinates
are constant across points.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_OFFSET_FILL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled, and if the polygon is rendered in
<constant>GL_FILL</constant> mode, an offset is added to depth values of a polygon's
fragments before the depth comparison is performed.
See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_OFFSET_LINE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled, and if the polygon is rendered in
<constant>GL_LINE</constant> mode, an offset is added to depth values of a polygon's
fragments before the depth comparison is performed.
See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_OFFSET_POINT</constant></term>
<listitem>
<para>
</para>
<para>
If enabled, an offset is added to depth values of a polygon's fragments
before the depth comparison is performed, if the polygon is rendered in
<constant>GL_POINT</constant> mode. See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_SMOOTH</constant></term>
<listitem>
<para>
</para>
<para>
If enabled, draw polygons with proper filtering.
Otherwise, draw aliased polygons. For correct antialiased polygons,
an alpha buffer is needed and the polygons must be sorted front to
back.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_STIPPLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
use the current polygon stipple pattern when rendering
polygons. See <citerefentry><refentrytitle>glPolygonStipple</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POST_COLOR_MATRIX_COLOR_TABLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
perform a color table lookup on RGBA color values after color matrix
transformation.
See <citerefentry><refentrytitle>glColorTable</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POST_CONVOLUTION_COLOR_TABLE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
perform a color table lookup on RGBA color values after convolution.
See <citerefentry><refentrytitle>glColorTable</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_RESCALE_NORMAL</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
normal vectors are scaled after transformation and before
lighting by a factor computed from the modelview matrix. If the
modelview matrix scales space uniformly, this has the effect of
restoring the transformed normal to unit length. This method is generally
more efficient than <constant>GL_NORMALIZE</constant>. See
<citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry> and
<citerefentry><refentrytitle>glNormalPointer</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
compute a temporary coverage value where each bit is determined by the
alpha value at the corresponding sample location. The temporary coverage
value is then ANDed with the fragment coverage value.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_SAMPLE_ALPHA_TO_ONE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
each sample alpha value is replaced by the maximum representable alpha value.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_SAMPLE_COVERAGE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
the fragment's coverage is ANDed with the temporary coverage value. If
<constant>GL_SAMPLE_COVERAGE_INVERT</constant> is set to <constant>GL_TRUE</constant>, invert the coverage
value.
See <citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_SEPARABLE_2D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled, perform a two-dimensional convolution operation using a separable
convolution filter on incoming RGBA color values.
See <citerefentry><refentrytitle>glSeparableFilter2D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_SCISSOR_TEST</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
discard fragments that are outside the scissor rectangle.
See <citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_STENCIL_TEST</constant></term>
<listitem>
<para>
</para>
<para>
If enabled,
do stencil testing and update the stencil buffer.
See <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_1D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
one-dimensional texturing is performed
(unless two- or three-dimensional or cube-mapped texturing is also enabled).
See <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_2D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
two-dimensional texturing is performed
(unless three-dimensional or cube-mapped texturing is also enabled).
See <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_3D</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
three-dimensional texturing is performed
(unless cube-mapped texturing is also enabled).
See <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_CUBE_MAP</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no fragment shader is active,
cube-mapped texturing is performed.
See <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_GEN_Q</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
the <emphasis>q</emphasis> texture coordinate is computed using
the texture generation function defined with <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
Otherwise, the current <emphasis>q</emphasis> texture coordinate is used.
See <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_GEN_R</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
the <emphasis>r</emphasis> texture coordinate is computed using
the texture generation function defined with <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
Otherwise, the current <emphasis>r</emphasis> texture coordinate is used.
See <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_GEN_S</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
the <emphasis>s</emphasis> texture coordinate is computed using
the texture generation function defined with <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
Otherwise, the current <emphasis>s</emphasis> texture coordinate is used.
See <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_GEN_T</constant></term>
<listitem>
<para>
</para>
<para>
If enabled and no vertex shader is active,
the <emphasis>t</emphasis> texture coordinate is computed using
the texture generation function defined with <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
Otherwise, the current <emphasis>t</emphasis> texture coordinate is used.
See <citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_VERTEX_PROGRAM_POINT_SIZE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled
and a vertex shader is active, then the derived point size is taken from the (potentially clipped) shader builtin
<constant>gl_PointSize</constant> and clamped to the implementation-dependent point size range.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_VERTEX_PROGRAM_TWO_SIDE</constant></term>
<listitem>
<para>
</para>
<para>
If enabled
and a vertex shader is active, it specifies that the GL will choose between front and back colors based on the
polygon's face direction of which the vertex being shaded is a part. It has no effect on points or lines.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
<constant>GL_POLYGON_OFFSET_FILL</constant>, <constant>GL_POLYGON_OFFSET_LINE</constant>,
<constant>GL_POLYGON_OFFSET_POINT</constant>,
<constant>GL_COLOR_LOGIC_OP</constant>, and <constant>GL_INDEX_LOGIC_OP</constant> are available
only if the GL version is 1.1 or greater.
</para>
<para>
<constant>GL_RESCALE_NORMAL</constant>, and <constant>GL_TEXTURE_3D</constant> are available only if the
GL version is 1.2 or greater.
</para>
<para>
<constant>GL_MULTISAMPLE</constant>,
<constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant>,
<constant>GL_SAMPLE_ALPHA_TO_ONE</constant>,
<constant>GL_SAMPLE_COVERAGE</constant>,
<constant>GL_TEXTURE_CUBE_MAP</constant>
are available only if the GL version is 1.3 or greater.
</para>
<para>
<constant>GL_POINT_SPRITE</constant>,
<constant>GL_VERTEX_PROGRAM_POINT_SIZE</constant>, and
<constant>GL_VERTEX_PROGRAM_TWO_SIDE</constant>
is available only if the GL version is 2.0 or greater.
</para>
<para>
<constant>GL_COLOR_TABLE</constant>, <constant>GL_CONVOLUTION_1D</constant>, <constant>GL_CONVOLUTION_2D</constant>,
<constant>GL_HISTOGRAM</constant>, <constant>GL_MINMAX</constant>,
<constant>GL_POST_COLOR_MATRIX_COLOR_TABLE</constant>,
<constant>GL_POST_CONVOLUTION_COLOR_TABLE</constant>, and
<constant>GL_SEPARABLE_2D</constant> are available only if <code>ARB_imaging</code> is returned
from <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_EXTENSIONS</constant>.
</para>
<para>
For OpenGL versions 1.3 and greater, or when <code>ARB_multitexture</code> is supported, <constant>GL_TEXTURE_1D</constant>,
<constant>GL_TEXTURE_2D</constant>, <constant>GL_TEXTURE_3D</constant>, <constant>GL_TEXTURE_GEN_S</constant>,
<constant>GL_TEXTURE_GEN_T</constant>, <constant>GL_TEXTURE_GEN_R</constant>, and <constant>GL_TEXTURE_GEN_Q</constant>
enable or disable the respective state for the active texture unit
specified with <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>cap</parameter> is not one of the values
listed previously.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glEnable</function> or <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glClipPlane</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glColorMaterial</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCullFace</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEnableClientState</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glFog</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glLight</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glLightModel</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glLineWidth</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glLineStipple</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMaterial</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glNormalPointer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPointSize</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPolygonMode</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glPolygonStipple</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>