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<?xml version="1.0" encoding="UTF-8"?>
< !DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<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>
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<refsynopsisdiv > <title > C Specification</title>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glEnablei</function> </funcdef>
<paramdef > GLenum <parameter > cap</parameter> </paramdef>
<paramdef > GLuint <parameter > index</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id= "parameters3" > <title > Parameters</title>
<variablelist >
<varlistentry >
<term > <parameter > cap</parameter> </term>
<listitem >
<para >
Specifies a symbolic constant indicating a GL capability.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > index</parameter> </term>
<listitem >
<para >
Specifies the index of the swtich to enable.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsynopsisdiv > <title > C Specification</title>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glDisablei</function> </funcdef>
<paramdef > GLenum <parameter > cap</parameter> </paramdef>
<paramdef > GLuint <parameter > index</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id= "parameters4" > <title > Parameters</title>
<variablelist >
<varlistentry >
<term > <parameter > cap</parameter> </term>
<listitem >
<para >
Specifies a symbolic constant indicating a GL capability.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > index</parameter> </term>
<listitem >
<para >
Specifies the index of the swtich to disable.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
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<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
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exception of <constant > GL_DITHER</constant> and <constant > GL_MULTISAMPLE</constant> is
<constant > GL_FALSE</constant> . The initial value for
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<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>
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<para >
Some of the GL's capabilities are indicated. <function > glEnablei</function> and <function > glDisablei</function> enable and disable
indexed capabilities.
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_BLEND</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<term > <constant > GL_CLIP_DISTANCE</constant> <emphasis > i</emphasis> </term>
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<listitem >
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<para >
</para>
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<para >
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If enabled, clip geometry against user-defined half space <emphasis > i</emphasis> .
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_COLOR_LOGIC_OP</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<term > <constant > GL_CULL_FACE</constant> </term>
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<listitem >
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<para >
</para>
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<para >
If enabled,
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cull polygons based on their winding in window coordinates.
See <citerefentry > <refentrytitle > glCullFace</refentrytitle> </citerefentry> .
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</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <constant > GL_DEPTH_CLAMP</constant> </term>
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<listitem >
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<para >
</para>
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<para >
If enabled,
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the
<!-- - wc <= zc <= wc -->
<inlineequation > <mml:math >
<mml:mo > -</mml:mo> <mml:msub > <mml:mi > w</mml:mi> <mml:mi > c</mml:mi> </mml:msub> <mml:mo > ≤ </mml:mo> <mml:msub > <mml:mi > z</mml:mi> <mml:mi > c</mml:mi> </mml:msub> <mml:mo > ≤ </mml:mo> <mml:msub > <mml:mi > w</mml:mi> <mml:mi > c</mml:mi> </mml:msub>
</mml:math> </inlineequation>
plane equation is ignored by view volume clipping (effectively, there is no near or
far plane clipping).
See <citerefentry > <refentrytitle > glDepthRange</refentrytitle> </citerefentry> .
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_DEPTH_TEST</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<term > <constant > GL_DITHER</constant> </term>
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<listitem >
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<para >
</para>
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<para >
If enabled,
dither color components or indices before they are written to the
color buffer.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_LINE_SMOOTH</constant> </term>
<listitem >
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<para >
</para>
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<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_MULTISAMPLE</constant> </term>
<listitem >
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<para >
</para>
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<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_POLYGON_OFFSET_FILL</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<para >
</para>
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<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 >
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<para >
</para>
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<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 >
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<para >
</para>
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<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 >
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<term > <constant > GL_PRIMITIVE_RESTART</constant> </term>
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<listitem >
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<para >
</para>
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<para >
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Enables primitive restarting. If enabled, any one of the draw commands
which transfers a set of generic attribute array elements to the GL will restart
the primitive when the index of the vertex is equal to the primitive restart index.
See <citerefentry > <refentrytitle > glPrimitiveRestartIndex</refentrytitle> </citerefentry> .
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_SAMPLE_ALPHA_TO_COVERAGE</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<para >
</para>
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<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 >
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<para >
</para>
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<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_SCISSOR_TEST</constant> </term>
<listitem >
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<para >
</para>
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<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 >
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<para >
</para>
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<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 >
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<term > <constant > GL_TEXTURE_CUBE_MAP_SEAMLESS</constant> </term>
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<listitem >
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<para >
</para>
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<para >
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If enabled, modifies the way sampling is performed on cube map textures. See the spec for more information.
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</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <constant > GL_PROGRAM_POINT_SIZE</constant> </term>
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<listitem >
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<para >
</para>
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<para >
If enabled
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and a vertex or geometry shader is active, then the derived point size is taken from the (potentially clipped) shader builtin
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<constant > gl_PointSize</constant> and clamped to the implementation-dependent point size range.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
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<refsect1 id= "errors" > <title > Errors</title>
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<para >
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<constant > GL_INVALID_ENUM</constant> is generated if <parameter > cap</parameter> is not one of the values
listed previously.
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</para>
<para >
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<constant > GL_INVALID_VALUE</constant> is generated by <function > glEnablei</function> and <function > glDisablei</function>
if <parameter > index</parameter> is greater than or equal to the number of indexed capabilities for <parameter > cap</parameter> .
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</para>
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</refsect1>
<refsect1 id= "notes" > <title > Notes</title>
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<para >
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<constant > GL_PRIMITIVE_RESTART</constant> is available only if the GL version is 3.1 or greater.
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</para>
<para >
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<constant > GL_TEXTURE_CUBE_MAP_SEAMLESS</constant> is available only if the GL version is 3.2 or greater.
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</para>
<para >
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Any token accepted by <function > glEnable</function> or <function > glDisable</function> is also accepted by
<function > glEnablei</function> and <function > glDisablei</function> , but if the capability is not indexed,
the maximum value that <parameter > index</parameter> may take is zero.
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</para>
<para >
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In general, passing an indexed capability to <function > glEnable</function> or <function > glDisable</function>
will enable or disable that capability for all indices, resepectively.
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</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 > glBlendFunc</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCullFace</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glDepthFunc</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glDepthRange</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glGet</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glIsEnabled</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glLineWidth</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glLogicOp</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glPointSize</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glPolygonMode</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glPolygonOffset</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glSampleCoverage</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glScissor</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glStencilFunc</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glStencilOp</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
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Silicon Graphics, Inc. Copyright <trademark class= "copyright" > </trademark> 2010 Khronos Group.
This document is licensed under the SGI
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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>
