upstream-man-pages/manglsl/xhtml/gl_FragCoord.xml

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   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_FragCoord - 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_FragCoord"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gl_FragCoord — contains the window-relative coordinates of the current fragment</p></div><div class="refsynopsisdiv"><h2>Declaration</h2><div class="funcsynopsis"><code class="function">in vec4 gl_FragCoord;</code></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
   5             Available only in the fragment language, <code class="function">gl_FragCoord</code> is an input variable that contains the
   6             window relative coordinate (x, y, z, 1/w) values for the fragment. If multi-sampling,
   7             this value can be for any location within the pixel, or one of the fragment samples.
   8             This value is the result of fixed functionality that interpolates primitives after vertex
   9             processing to generate fragments. The z component is the depth value that would be used for the
  10             fragment's depth if no shader contained any writes to <a href="gl_FragDepth.xml"><span class="citerefentry"><span class="refentrytitle">gl_FragDepth</span></span></a>.
  11         </p><p>
  12             <code class="function">gl_FragCoord</code> may be redeclared with the additional layout qualifier identifiers
  13             <code class="function">origin_upper_left</code> or <code class="function">pixel_center_integer</code>. By
  14             default, <code class="function">gl_FragCoord</code> assumes a lower-left origin for window coordinates
  15             and assumes pixel centers are located at half-pixel centers. For example, the (x, y) location
  16             (0.5, 0.5) is returned for the lower-left-most pixel in a window. The origin of
  17             <code class="function">gl_FragCoord</code> may be changed by redeclaring <code class="function">gl_FragCoord</code>
  18             with the <code class="function">origin_upper_left</code> identifier. The values returned can also be
  19             shifted by half a pixel in both x and y by <code class="function">pixel_center_integer</code> so it
  20             appears the pixels are centered at whole number pixel offsets. This moves the (x, y) value returned by
  21             <code class="function">gl_FragCoord</code> of (0.5, 0.5) by default to (0.0, 0.0) with
  22             <code class="function">pixel_center_integer</code>.
  23         </p><p>
  24             If <code class="function">gl_FragCoord</code> is redeclared in any fragment shader in a program, it must be redeclared
  25             in all fragment shaders in that program that have static use of <code class="function">gl_FragCoord</code>. Redeclaring
  26             <code class="function">gl_FragCoord</code> with any accepted qualifier affects only <code class="function">gl_FragCoord.x</code>
  27             and <code class="function">gl_FragCoord.y</code>. It has no affect on rasterization, transformation or any other part
  28             of the OpenGL pipline or language features.
  29         </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>Variable</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_ClipDistance</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><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></thead></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
  30             <a href="gl_FragCoord.xml"><span class="citerefentry"><span class="refentrytitle">gl_FragCoord</span></span></a>
  31         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
  32             Copyright <span class="trademark"></span>© 2011 Khronos Group.
  33             This material may be distributed subject to the terms and conditions set forth in
  34             the Open Publication License, v 1.0, 8 June 1999.
  35             <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
  36         </p></div></div></body></html>