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rename upstream-man-pages to upstream-doc
[clinton/guile-figl.git] / upstream-doc / manglsl / xhtml / gl_FrontFacing.xml
diff --git a/upstream-doc/manglsl/xhtml/gl_FrontFacing.xml b/upstream-doc/manglsl/xhtml/gl_FrontFacing.xml
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+++ b/upstream-doc/manglsl/xhtml/gl_FrontFacing.xml
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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
+<!-- saved from url=(0013)about:internet -->
+<?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_FrontFacing - 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_FrontFacing"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gl_FrontFacing — indicates whether a primitive is front or back facing</p></div><div class="refsynopsisdiv"><h2>Declaration</h2><div class="funcsynopsis"><code class="function">in bool gl_FrontFacing;</code></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
+            Available only in the fragment language, <code class="function">gl_FrontFacing</code> is an input variable
+            whose value is <code class="function">true</code> if the fragment belongs to a front-facing primitive and
+            false otherwise. The determination of whether a triangle primitive is front-facing is made by
+            examining the sign of the area of the triangle, including a possible reversal of this sign
+            as controlled by <code class="function">glFrontFace</code>. One way to compute this area is:
+        </p><p>
+            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
+                <mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mfrac><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:mfrac>
+                <mml:msubsup><mml:mo>∑</mml:mo><mml:mrow>
+                    <mml:mi>j</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn>
+                </mml:mrow>
+                <mml:mrow>
+                    <mml:mi>n</mml:mi><mml:mo>-</mml:mo><mml:mn>1</mml:mn>
+                </mml:mrow></mml:msubsup>
+                <mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>
+                <mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>
+                <mml:mo>-</mml:mo>
+                <mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup>
+                <mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup>
+            </mml:math>
+        </p><p>
+            where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msubsup><mml:mi>x</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math> and
+            <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msubsup><mml:mi>y</mml:mi><mml:mrow>w</mml:mrow><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msubsup></mml:math> are
+            the x and y window coordinates of the <span class="emphasis"><em>i</em></span>th vertex of the n-vertex polygon.
+        </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" /></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></tr><tr><th align="left">
+                            gl_FrontFacing
+                        </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>
+            <a href="gl_FragCoord.xml"><span class="citerefentry"><span class="refentrytitle">gl_FragCoord</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>© 2011 Khronos Group. 
+            This material may be distributed subject to the terms and conditions set forth in 
+            the Open Publication License, v 1.0, 8 June 1999.
+            <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
+        </p></div></div></body></html>
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