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<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glEnable - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glEnable"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glEnable — enable or disable server-side GL capabilities</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glEnable</b>(</code>GLenum <var class="pdparam">cap</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>cap</code></em></span></dt><dd><p>
                    Specifies a symbolic constant indicating a GL capability.
                </p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glDisable</b>(</code>GLenum <var class="pdparam">cap</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>cap</code></em></span></dt><dd><p>
                    Specifies a symbolic constant indicating a GL capability.
                </p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glEnablei</b>(</code>GLenum <var class="pdparam">cap</var>, GLuint <var class="pdparam">index</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters3"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>cap</code></em></span></dt><dd><p>
                    Specifies a symbolic constant indicating a GL capability.
                </p></dd><dt><span class="term"><em class="parameter"><code>index</code></em></span></dt><dd><p>
                    Specifies the index of the swtich to enable.
                </p></dd></dl></div></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glDisablei</b>(</code>GLenum <var class="pdparam">cap</var>, GLuint <var class="pdparam">index</var><code>)</code>;</p></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters4"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>cap</code></em></span></dt><dd><p>
                    Specifies a symbolic constant indicating a GL capability.
                </p></dd><dt><span class="term"><em class="parameter"><code>index</code></em></span></dt><dd><p>
                    Specifies the index of the swtich to disable.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glEnable</code> and <a href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> enable and disable various capabilities.
            Use <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> or <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> to determine the current setting
            of any capability. The initial value for each capability with the
            exception of <code class="constant">GL_DITHER</code> and <code class="constant">GL_MULTISAMPLE</code> is
            <code class="constant">GL_FALSE</code>. The initial value for
            <code class="constant">GL_DITHER</code> and <code class="constant">GL_MULTISAMPLE</code> is <code class="constant">GL_TRUE</code>.
        </p><p>
            Both <code class="function">glEnable</code> and <a href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> take a single argument, <em class="parameter"><code>cap</code></em>,
            which can assume one of the following values:
        </p><p>
            Some of the GL's capabilities are indexed. <code class="function">glEnablei</code> and <code class="function">glDisablei</code> enable and disable
            indexed capabilities.
        </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_BLEND</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        blend the computed fragment color values with the values in the color
                        buffers. See <a href="glBlendFunc.xml"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_CLIP_DISTANCE</code><span class="emphasis"><em>i</em></span></span></dt><dd><p>
                </p><p>
                        If enabled, clip geometry against user-defined half space <span class="emphasis"><em>i</em></span>.
                    </p></dd><dt><span class="term"><code class="constant">GL_COLOR_LOGIC_OP</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        apply the currently selected logical operation to the computed fragment
                        color and color buffer values. See <a href="glLogicOp.xml"><span class="citerefentry"><span class="refentrytitle">glLogicOp</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_CULL_FACE</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        cull polygons based on their winding in window coordinates.
                        See <a href="glCullFace.xml"><span class="citerefentry"><span class="refentrytitle">glCullFace</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_DEBUG_OUTPUT</code></span></dt><dd><p>
                </p><p>
                        If enabled, debug messages are produced by a debug context. When disabled,
                        the debug message log is silenced. Note that in a non-debug context, very
                        few, if any messages might be produced, even when <code class="constant">GL_DEBUG_OUTPUT</code>
                        is enabled.
                    </p></dd><dt><span class="term"><code class="constant">GL_DEBUG_OUTPUT_SYNCHRONOUS</code></span></dt><dd><p>
                </p><p>
                        If enabled, debug messages are produced synchronously by a debug context. If disabled,
                        debug messages may be produced asynchronously. In particular, they may be delayed relative
                        to the execution of GL commands, and the debug callback function may be called from
                        a thread other than that in which the commands are executed.
                        See <a href="glDebugMessageCallback.xml"><span class="citerefentry"><span class="refentrytitle">glDebugMessageCallback</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_CLAMP</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        the
                        
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                        </mml:math>
                        plane equation is ignored by view volume clipping (effectively, there is no near or
                        far plane clipping).
                        See <a href="glDepthRange.xml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_TEST</code></span></dt><dd><p>
                </p><p>
                        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
                        <a href="glDepthFunc.xml"><span class="citerefentry"><span class="refentrytitle">glDepthFunc</span></span></a> and
                        <a href="glDepthRange.xml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_DITHER</code>    </span></dt><dd><p>
                </p><p>
                        If enabled,
                        dither color components or indices before they are written to the
                        color buffer.
                    </p></dd><dt><span class="term"><code class="constant">GL_FRAMEBUFFER_SRGB</code>    </span></dt><dd><p>
                </p><p>
                        If enabled
                        and the value of <code class="constant">GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING</code> for the
                        framebuffer attachment corresponding to the destination buffer is <code class="constant">GL_SRGB</code>,
                        the R, G, and B destination color values (after conversion from fixed-point to floating-point)
                        are considered to be encoded for the sRGB color space and hence are linearized prior to
                        their use in blending.
                    </p></dd><dt><span class="term"><code class="constant">GL_LINE_SMOOTH</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        draw lines with correct filtering.
                        Otherwise,
                        draw aliased lines.
                        See <a href="glLineWidth.xml"><span class="citerefentry"><span class="refentrytitle">glLineWidth</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_MULTISAMPLE</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        use multiple fragment samples in computing the final color of a pixel.
                        See <a href="glSampleCoverage.xml"><span class="citerefentry"><span class="refentrytitle">glSampleCoverage</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_POLYGON_OFFSET_FILL</code></span></dt><dd><p>
                </p><p>
                        If enabled, and if the polygon is rendered in
                        <code class="constant">GL_FILL</code> mode, an offset is added to depth values of a polygon's
                        fragments before the depth comparison is performed.
                        See <a href="glPolygonOffset.xml"><span class="citerefentry"><span class="refentrytitle">glPolygonOffset</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_POLYGON_OFFSET_LINE</code></span></dt><dd><p>
                </p><p>
                        If enabled, and if the polygon is rendered in
                        <code class="constant">GL_LINE</code> mode, an offset is added to depth values of a polygon's
                        fragments before the depth comparison is performed.
                        See <a href="glPolygonOffset.xml"><span class="citerefentry"><span class="refentrytitle">glPolygonOffset</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_POLYGON_OFFSET_POINT</code></span></dt><dd><p>
                </p><p>
                        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
                        <code class="constant">GL_POINT</code> mode. See <a href="glPolygonOffset.xml"><span class="citerefentry"><span class="refentrytitle">glPolygonOffset</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_POLYGON_SMOOTH</code></span></dt><dd><p>
                </p><p>
                        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.
                    </p></dd><dt><span class="term"><code class="constant">GL_PRIMITIVE_RESTART</code></span></dt><dd><p>
                </p><p>
                        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 <a href="glPrimitiveRestartIndex.xml"><span class="citerefentry"><span class="refentrytitle">glPrimitiveRestartIndex</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_PRIMITIVE_RESTART_FIXED_INDEX</code></span></dt><dd><p>
                </p><p>
                        Enables primitive restarting with a fixed index. 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 fixed primitive
                        index for the specified index type. The fixed index is equal to
                        <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msup><mml:mn>2</mml:mn><mml:mi>n</mml:mi></mml:msup><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:math>
                        where <span class="emphasis"><em>n</em></span> is equal to 8 for <code class="constant">GL_UNSIGNED_BYTE</code>,
                        16 for <code class="constant">GL_UNSIGNED_SHORT</code> and 32 for <code class="constant">GL_UNSIGNED_INT</code>.
                    </p></dd><dt><span class="term"><code class="constant">GL_SAMPLE_ALPHA_TO_COVERAGE</code></span></dt><dd><p>
                </p><p>
                        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.
                    </p></dd><dt><span class="term"><code class="constant">GL_SAMPLE_ALPHA_TO_ONE</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        each sample alpha value is replaced by the maximum representable alpha value.
                    </p></dd><dt><span class="term"><code class="constant">GL_SAMPLE_COVERAGE</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        the fragment's coverage is ANDed with the temporary coverage value.  If
                        <code class="constant">GL_SAMPLE_COVERAGE_INVERT</code> is set to <code class="constant">GL_TRUE</code>, invert the coverage
                        value.
                        See <a href="glSampleCoverage.xml"><span class="citerefentry"><span class="refentrytitle">glSampleCoverage</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_SAMPLE_SHADING</code></span></dt><dd><p>
                </p><p>
                        If enabled, the active fragment shader is run once for each covered sample, or at
                        fraction of this rate as determined by the current value of <code class="constant">GL_MIN_SAMPLE_SHADING_VALUE</code>.
                        See <a href="glMinSampleShading.xml"><span class="citerefentry"><span class="refentrytitle">glMinSampleShading</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_SAMPLE_MASK</code></span></dt><dd><p>
                </p><p>
                        If enabled, the sample coverage mask generated for a fragment during rasterization
                        will be ANDed with the value of <code class="constant">GL_SAMPLE_MASK_VALUE</code> before
                        shading occurs.
                        See <a href="glSampleMaski.xml"><span class="citerefentry"><span class="refentrytitle">glSampleMaski</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_SCISSOR_TEST</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        discard fragments that are outside the scissor rectangle.
                        See <a href="glScissor.xml"><span class="citerefentry"><span class="refentrytitle">glScissor</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_STENCIL_TEST</code></span></dt><dd><p>
                </p><p>
                        If enabled,
                        do stencil testing and update the stencil buffer.
                        See <a href="glStencilFunc.xml"><span class="citerefentry"><span class="refentrytitle">glStencilFunc</span></span></a> and <a href="glStencilOp.xml"><span class="citerefentry"><span class="refentrytitle">glStencilOp</span></span></a>.
                    </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_CUBE_MAP_SEAMLESS</code></span></dt><dd><p>
                </p><p>
                        If enabled, cubemap textures are sampled such that when linearly sampling from the border
                        between two adjacent faces, texels from both faces are used to generate the final sample
                        value. When disabled, texels from only a single face are used to construct the final
                        sample value.
                    </p></dd><dt><span class="term"><code class="constant">GL_PROGRAM_POINT_SIZE</code></span></dt><dd><p>
                </p><p>
                        If enabled
                        and a vertex or geometry shader is active, then the derived point size is taken from the (potentially clipped) shader builtin
                        <code class="constant">gl_PointSize</code> and clamped to the implementation-dependent point size range.
                    </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>cap</code></em> is not one of the values
            listed previously.
        </p><p>
            <code class="constant">GL_INVALID_VALUE</code> is generated by <code class="function">glEnablei</code> and <code class="function">glDisablei</code>
            if <em class="parameter"><code>index</code></em> is greater than or equal to the number of indexed capabilities for <em class="parameter"><code>cap</code></em>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
            <code class="constant">GL_PRIMITIVE_RESTART</code> is available only if the GL version is 3.1 or greater.
        </p><p>
            <code class="constant">GL_TEXTURE_CUBE_MAP_SEAMLESS</code> is available only if the GL version is 3.2 or greater.
        </p><p>
            <code class="constant">GL_PRIMITIVE_RESTART_FIXED_INDEX</code> is available only if the GL version is 4.3 or greater.
        </p><p>
            <code class="constant">GL_DEBUG_OUTPUT</code> and <code class="constant">GL_DEBUG_OUTPUT_SYNCHRONOUS</code> are available only if the GL version is 4.3 or greater.
        </p><p>
            Any token accepted by <code class="function">glEnable</code> or <code class="function">glDisable</code> is also accepted by
            <code class="function">glEnablei</code> and <code class="function">glDisablei</code>, but if the capability is not indexed,
            the maximum value that <em class="parameter"><code>index</code></em> may take is zero.
        </p><p>
            In general, passing an indexed capability to <code class="function">glEnable</code> or <code class="function">glDisable</code>
            will enable or disable that capability for all indices, resepectively.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
            <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a>
        </p><p>
            <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a href="glActiveTexture.xml"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>,
            <a href="glBlendFunc.xml"><span class="citerefentry"><span class="refentrytitle">glBlendFunc</span></span></a>,
            <a href="glCullFace.xml"><span class="citerefentry"><span class="refentrytitle">glCullFace</span></span></a>,
            <a href="glDepthFunc.xml"><span class="citerefentry"><span class="refentrytitle">glDepthFunc</span></span></a>,
            <a href="glDepthRange.xml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>,
            <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>,
            <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a>,
            <a href="glLineWidth.xml"><span class="citerefentry"><span class="refentrytitle">glLineWidth</span></span></a>,
            <a href="glLogicOp.xml"><span class="citerefentry"><span class="refentrytitle">glLogicOp</span></span></a>,
            <a href="glPointSize.xml"><span class="citerefentry"><span class="refentrytitle">glPointSize</span></span></a>,
            <a href="glPolygonMode.xml"><span class="citerefentry"><span class="refentrytitle">glPolygonMode</span></span></a>,
            <a href="glPolygonOffset.xml"><span class="citerefentry"><span class="refentrytitle">glPolygonOffset</span></span></a>,
            <a href="glSampleCoverage.xml"><span class="citerefentry"><span class="refentrytitle">glSampleCoverage</span></span></a>,
            <a href="glScissor.xml"><span class="citerefentry"><span class="refentrytitle">glScissor</span></span></a>,
            <a href="glStencilFunc.xml"><span class="citerefentry"><span class="refentrytitle">glStencilFunc</span></span></a>,
            <a href="glStencilOp.xml"><span class="citerefentry"><span class="refentrytitle">glStencilOp</span></span></a>,
            <a href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a>,
            <a href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>,
            <a href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a>
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 1991-2006
            Silicon Graphics, Inc. Copyright <span class="trademark"></span>© 2010-2011 Khronos Group.
            This document is licensed under the SGI
            Free Software B License. For details, see
            <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
        </p></div></div></body></html>
