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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_Layer - 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_Layer"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gl_Layer — contains the selected layer of a multi-layer framebuffer attachment</p></div><div class="refsynopsisdiv"><h2>Declaration</h2><div class="funcsynopsis"><code class="function">out int gl_Layer; // Geometry stage</code></div><div class="funcsynopsis"><code class="function">in int gl_Layer; // 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_Layer</code> is used to select a specific | |
6 | layer (or face and layer of cube map) in a multi-layer framebuffer attachment. The actual | |
7 | layer used will come from one of the vertices in the primitive being shaded. Which vertex | |
8 | the layer comes from is undefined and as such it is recommended to write the same value | |
9 | to <code class="function">gl_Layer</code> for all vertices in the primitive. If a shader statically | |
10 | assigns a value to <code class="function">gl_Layer</code>, layered rendering mode is enabled. | |
11 | If a shader statically assigns a value to <code class="function">gl_Layer</code>, and there is an execution path through | |
12 | the shader that does not set <code class="function">gl_Layer</code>, then the value of <code class="function">gl_Layer</code> | |
13 | is undefined for invocations of the shader that take that path. | |
14 | </p><p> | |
15 | When used with an array of cube map textures, the <code class="function">gl_Layer</code> output variable | |
16 | takes on a special value. Instead of referring to only the layer, it is used to select a cube map | |
17 | face and a layer. Setting <code class="function">gl_Layer</code> to the value | |
18 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>layer</mml:mi><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mi>face</mml:mi></mml:math> | |
19 | will render to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>face</mml:mi></mml:math> | |
20 | of the cube defined in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi>layer</mml:mi></mml:math>. | |
21 | The face values are as follows: | |
22 | </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong> | |
23 | Face Value | |
24 | </strong></span></th><th align="left"><span class="bold"><strong> | |
25 | Resulting Target | |
26 | </strong></span></th></tr><tr><th align="left"> | |
27 | 0 | |
28 | </th><th align="center"> | |
29 | <code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_X</code> | |
30 | </th></tr><tr><th align="left"> | |
31 | 1 | |
32 | </th><th align="center"> | |
33 | <code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_X</code> | |
34 | </th></tr><tr><th align="left"> | |
35 | 2 | |
36 | </th><th align="center"> | |
37 | <code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_Y</code> | |
38 | </th></tr><tr><th align="left"> | |
39 | 3 | |
40 | </th><th align="center"> | |
41 | <code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_Y</code> | |
42 | </th></tr><tr><th align="left"> | |
43 | 4 | |
44 | </th><th align="center"> | |
45 | <code class="constant">GL_TEXTURE_CUBEMAP_POSITIVE_Z</code> | |
46 | </th></tr><tr><th align="left"> | |
47 | 5 | |
48 | </th><th align="center"> | |
49 | <code class="constant">GL_TEXTURE_CUBEMAP_NEGATIVE_Z</code> | |
50 | </th></tr></thead></table></div><p> | |
51 | </p><p> | |
52 | For example, to render to the positive y cube map face located in the 5<sup>th</sup> layer of the | |
53 | cube map array, <code class="function">gl_Layer</code> should be set to | |
54 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mn>5</mml:mn><mml:mo>*</mml:mo><mml:mn>6</mml:mn><mml:mo>+</mml:mo><mml:mn>2</mml:mn></mml:math>. | |
55 | </p><p> | |
56 | The input variable <code class="function">gl_Layer</code> in the fragment language will have the same value that was written to the | |
57 | output variable <code class="function">gl_Layer</code> in the geometry language. If the geometry stage does not dynamically assign a | |
58 | value to <code class="function">gl_Layer</code>, the value of <code class="function">gl_Layer</code> in the fragment stage will be undefined. If the geometry stage | |
59 | makes no static assignment to <code class="function">gl_Layer</code>, the input <code class="function">gl_Layer</code> in the fragment stage will be zero. Otherwise, | |
60 | the fragment stage will read the same value written by the geometry stage, even if that value is out of | |
61 | range. If a fragment shader contains a static access to <code class="function">gl_Layer</code>, it will count against the implementation | |
62 | defined limit for the maximum number of inputs to the fragment stage. | |
63 | </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_Layer (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_Layer (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> | |
64 | <a href="gl_ViewportIndex.xml"><span class="citerefentry"><span class="refentrytitle">gl_ViewportIndex</span></span></a> | |
65 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
66 | Copyright <span class="trademark"></span>© 2011-2012 Khronos Group. | |
67 | This material may be distributed subject to the terms and conditions set forth in | |
68 | the Open Publication License, v 1.0, 8 June 1999. | |
69 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. | |
70 | </p></div></div></body></html> |