HCoop / clinton / guile-figl.git / blame
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1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> | |
| 3 | <!-- saved from url=(0013)about:internet --> | |
| 4 | <?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>gl_ViewportIndex - OpenGL Shading Language (GLSL)</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gl_ViewportIndex"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gl_ViewportIndex — contains the index of the viewport to be used in viewport transformation and scissoring</p></div><div class="refsynopsisdiv"><h2>Declaration</h2><div class="funcsynopsis"><code class="function">out int gl_ViewportIndex; // Geometry stage</code></div><div class="funcsynopsis"><code class="function">in int gl_ViewportIndex; // Fragment stage</code></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
| 5 | In the geometry language, <code class="function">gl_ViewportIndex</code> is used to specify the index | |
| 6 | of the viewport to which the next primitive emitted from the shader should be drawn. Primitives generated | |
| 7 | by the geometry shader will undergo viewport transformation and scissor testing using the viewport | |
| 8 | transformation and scissor rectangle selected by the value of <code class="function">gl_ViewportIndex</code>. | |
| 9 | The viewport index used will come from one of the vertices in the primitive being shaded. However, which | |
| 10 | vertex the viewport index comes from is implementation-defined, and so it is recommended to use the same | |
| 11 | viewport index for all vertices of a primitive. If a geometry shader does not assign a value to | |
| 12 | <code class="function">gl_ViewportIndex</code>, viewport transform and scissor rectangle zero will be used. | |
| 13 | If a geometry shader statically assigns a value to <code class="function">gl_ViewportIndex</code> and there | |
| 14 | is a path through the shader that does not assign a value to <code class="function">gl_ViewportIndex</code>, | |
| 15 | the value of <code class="function">gl_ViewportIndex</code> is undefined for executions of the shader that take | |
| 16 | that path. | |
| 17 | </p><p> | |
| 18 | In the fragment language, <code class="function">gl_ViewportIndex</code> will have the same value that was written to the | |
| 19 | output variable <code class="function">gl_ViewportIndex</code> in the geometry stage. If the geometry stage does not dynamically | |
| 20 | assign to <code class="function">gl_ViewportIndex</code>, the value of <code class="function">gl_ViewportIndex</code> in the fragment shader will be undefined. If | |
| 21 | the geometry stage makes no static assignment to <code class="function">gl_ViewportIndex</code>, the fragment stage will read zero. | |
| 22 | Otherwise, the fragment stage will read the same value written by the geometry stage, even if that value is | |
| 23 | out of range. If a fragment shader contains a static access to <code class="function">gl_ViewportIndex</code>, it will count against the | |
| 24 | implementation defined limit for the maximum number of inputs to the fragment stage. | |
| 25 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="versions"></a><h2>Version Support</h2><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>Function</strong></span></th><th align="left"><span class="bold"><strong>Version 1.10</strong></span></th><th align="left"><span class="bold"><strong>Version 1.20</strong></span></th><th align="left"><span class="bold"><strong>Version 1.30</strong></span></th><th align="left"><span class="bold"><strong>Version 1.40</strong></span></th><th align="left"><span class="bold"><strong>Version 1.50</strong></span></th><th align="left"><span class="bold"><strong>Version 3.30</strong></span></th><th align="left"><span class="bold"><strong>Version 4.00</strong></span></th><th align="left"><span class="bold"><strong>Version 4.10</strong></span></th><th align="left"><span class="bold"><strong>Version 4.20</strong></span></th><th align="center"><span class="bold"><strong>Version 4.30</strong></span></th></tr><tr><th align="left">gl_ViewportIndex (geometry stage)</th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr><tr><th align="left">gl_ViewportIndex (fragment stage)</th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>-</em></span></th><th align="center"><span class="emphasis"><em>Y</em></span></th></tr></thead></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
| 26 | <a href="gl_Layer.xml"><span class="citerefentry"><span class="refentrytitle">gl_Layer</span></span></a> | |
| 27 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
| 28 | Copyright <span class="trademark"></span>© 2011 Khronos Group. | |
| 29 | This material may be distributed subject to the terms and conditions set forth in | |
| 30 | the Open Publication License, v 1.0, 8 June 1999. | |
| 31 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
| 32 | </p></div></div></body></html> |