rename upstream-man-pages to upstream-doc

[clinton/guile-figl.git] / upstream-doc / manglsl / gl_ViewportIndex.xml

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+<?xml version="1.0" encoding="UTF-8"?>\r
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"\r
+              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">\r
+<refentry id="gl_ViewportIndex">\r
+    <refmeta>\r
+        <refmetainfo>\r
+            <copyright>\r
+                <year>2011</year>\r
+                <holder>Khronos Group</holder>\r
+            </copyright>\r
+        </refmetainfo>\r
+        <refentrytitle>gl_ViewportIndex</refentrytitle>\r
+        <manvolnum>3G</manvolnum>\r
+    </refmeta>\r
+    <refnamediv>\r
+        <refname>gl_ViewportIndex</refname>\r
+        <refpurpose>contains the index of the viewport to be used in viewport transformation and scissoring</refpurpose>\r
+    </refnamediv>\r
+    <refsynopsisdiv><title>Declaration</title>\r
+        <funcsynopsis>\r
+            <function>out int gl_ViewportIndex; // Geometry stage</function>\r
+        </funcsynopsis>\r
+        <funcsynopsis>\r
+            <function>in  int gl_ViewportIndex; // Fragment stage</function>\r
+        </funcsynopsis>\r
+    </refsynopsisdiv>\r
+    <refsect1 id="description"><title>Description</title>\r
+        <para>\r
+            In the geometry language, <function>gl_ViewportIndex</function> is used to specify the index\r
+            of the viewport to which the next primitive emitted from the shader should be drawn. Primitives generated\r
+            by the geometry shader will undergo viewport transformation and scissor testing using the viewport\r
+            transformation and scissor rectangle selected by the value of <function>gl_ViewportIndex</function>.\r
+            The viewport index used will come from one of the vertices in the primitive being shaded. However, which\r
+            vertex the viewport index comes from is implementation-defined, and so it is recommended to use the same\r
+            viewport index for all vertices of a primitive. If a geometry shader does not assign a value to\r
+            <function>gl_ViewportIndex</function>, viewport transform and scissor rectangle zero will be used.\r
+            If a geometry shader statically assigns a value to <function>gl_ViewportIndex</function> and there\r
+            is a path through the shader that does not assign a value to <function>gl_ViewportIndex</function>,\r
+            the value of <function>gl_ViewportIndex</function> is undefined for executions of the shader that take\r
+            that path.\r
+        </para>\r
+        <para>\r
+            In the fragment language, <function>gl_ViewportIndex</function> will have the same value that was written to the \r
+            output variable <function>gl_ViewportIndex</function> in the geometry stage.  If the geometry stage does not dynamically\r
+            assign to <function>gl_ViewportIndex</function>, the value of <function>gl_ViewportIndex</function> in the fragment shader will be undefined. If\r
+            the geometry stage makes no static assignment to <function>gl_ViewportIndex</function>, the fragment stage will read zero.\r
+            Otherwise, the fragment stage will read the same value written by the geometry stage, even if that value is\r
+            out of range. If a fragment shader contains a static access to <function>gl_ViewportIndex</function>, it will count against the\r
+            implementation defined limit for the maximum number of inputs to the fragment stage.\r
+        </para>\r
+    </refsect1>\r
+    <refsect1 id="versions"><title>Version Support</title>\r
+        <informaltable frame="topbot">\r
+            #VARTABLECOLS#\r
+                <thead>\r
+                    #FUNCTABLEHEADER#\r
+                    <row>\r
+                        <entry>gl_ViewportIndex (geometry stage)</entry>#newin15#\r
+                    </row>\r
+                    <row>\r
+                        <entry>gl_ViewportIndex (fragment stage)</entry>#newin43#\r
+                    </row>\r
+                </thead>\r
+            </tgroup>\r
+        </informaltable>\r
+    </refsect1>\r
+    <refsect1 id="seealso"><title>See Also</title>\r
+        <para>\r
+            <citerefentry><refentrytitle>gl_Layer</refentrytitle></citerefentry>\r
+        </para>\r
+    </refsect1>\r
+    <refsect1 id="Copyright"><title>Copyright</title>\r
+        <para>\r
+            Copyright <trademark class="copyright"></trademark> 2011 Khronos Group. \r
+            This material may be distributed subject to the terms and conditions set forth in \r
+            the Open Publication License, v 1.0, 8 June 1999.\r
+            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.\r
+        </para>\r
+    </refsect1>\r
+</refentry>\r