upstream-doc/man2/xhtml/glShadeModel.xml

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
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   3 <?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" /><title>glShadeModel</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glShadeModel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glShadeModel — select flat or smooth shading</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glShadeModel</b>(</code></td><td>GLenum  </td><td><var class="pdparam">mode</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p>
   4                     Specifies a symbolic value representing a shading technique.
   5                     Accepted values are <code class="constant">GL_FLAT</code> and <code class="constant">GL_SMOOTH</code>.
   6                     The initial value is <code class="constant">GL_SMOOTH</code>.
   7                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
   8             GL primitives can have either flat or smooth shading.
   9             Smooth shading,
  10             the default,
  11             causes the computed colors of vertices to be interpolated as the
  12             primitive is rasterized,
  13             typically assigning different colors to each resulting pixel fragment.
  14             Flat shading selects the computed color of just one vertex
  15             and assigns it to all the pixel fragments
  16             generated by rasterizing a single primitive.
  17             In either case, the computed color of a vertex is the result of
  18             lighting if lighting is enabled,
  19             or it is the current color at the time the vertex was specified if
  20             lighting is disabled.
  21         </p><p>
  22             Flat and smooth shading are indistinguishable for points.
  23             Starting when <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> is issued and counting vertices and
  24             primitives from 1, the GL gives each flat-shaded line segment
  25             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
  26             the
  27             computed color of vertex
  28             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  29
  30                 <mml:mrow>
  31                     <mml:mi mathvariant="italic">i</mml:mi>
  32                     <mml:mo>+</mml:mo>
  33                     <mml:mn>1</mml:mn>
  34                 </mml:mrow>
  35             </mml:math>,
  36             its second vertex.
  37             Counting similarly from 1,
  38             the GL gives each flat-shaded polygon the computed color of the vertex listed
  39             in the following table.
  40             This is the last vertex to specify the polygon in all cases except single
  41             polygons,
  42             where the first vertex specifies the flat-shaded color.
  43         </p><p>
  44         </p><div class="informaltable"><table border="1"><colgroup><col align="left" /><col align="center" /></colgroup><thead><tr><th align="left"><span class="bold"><strong>
  45                         Primitive Type of Polygon
  46                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>
  47                         </strong></span></th><th align="center"><span class="bold"><strong>
  48                         Vertex
  49                         </strong></span></th></tr></thead><tbody><tr><td align="left">
  50                         Single polygon
  51                         (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  52
  53                             <mml:mrow>
  54                                 <mml:mi mathvariant="italic">i</mml:mi>
  55                                 <mml:mo>==</mml:mo>
  56                                 <mml:mn>1</mml:mn>
  57                             </mml:mrow>
  58                         </mml:math>)
  59                         </td><td align="center">
  60                         1
  61                         </td></tr><tr><td align="left">
  62                         Triangle strip
  63                         </td><td align="center">
  64                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  65
  66                             <mml:mrow>
  67                                 <mml:mi mathvariant="italic">i</mml:mi>
  68                                 <mml:mo>+</mml:mo>
  69                                 <mml:mn>2</mml:mn>
  70                             </mml:mrow>
  71                         </mml:math>
  72                         </td></tr><tr><td align="left">
  73                         Triangle fan
  74                         </td><td align="center">
  75                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  76
  77                             <mml:mrow>
  78                                 <mml:mi mathvariant="italic">i</mml:mi>
  79                                 <mml:mo>+</mml:mo>
  80                                 <mml:mn>2</mml:mn>
  81                             </mml:mrow>
  82                         </mml:math>
  83                         </td></tr><tr><td align="left">
  84                         Independent triangle
  85                         </td><td align="center">
  86                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  87
  88                             <mml:mrow>
  89                                 <mml:mn>3</mml:mn>
  90                                 <mml:mo>⁢</mml:mo>
  91                                 <mml:mi mathvariant="italic">i</mml:mi>
  92                             </mml:mrow>
  93                         </mml:math>
  94                         </td></tr><tr><td align="left">
  95                         Quad strip
  96                         </td><td align="center">
  97                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  98
  99                             <mml:mrow>
 100                                 <mml:mn>2</mml:mn>
 101                                 <mml:mo>⁢</mml:mo>
 102                                 <mml:mi mathvariant="italic">i</mml:mi>
 103                                 <mml:mo>+</mml:mo>
 104                                 <mml:mn>2</mml:mn>
 105                             </mml:mrow>
 106                         </mml:math>
 107                         </td></tr><tr><td align="left">
 108                         Independent quad
 109                         </td><td align="center">
 110                         <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 111
 112                             <mml:mrow>
 113                                 <mml:mn>4</mml:mn>
 114                                 <mml:mo>⁢</mml:mo>
 115                                 <mml:mi mathvariant="italic">i</mml:mi>
 116                             </mml:mrow>
 117                         </mml:math>
 118                         </td></tr></tbody></table></div><p>
 119             Flat and smooth shading are specified by <code class="function">glShadeModel</code> with <em class="parameter"><code>mode</code></em> set to
 120             <code class="constant">GL_FLAT</code> and <code class="constant">GL_SMOOTH</code>, respectively.
 121         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 122             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is any value other than
 123             <code class="constant">GL_FLAT</code> or <code class="constant">GL_SMOOTH</code>.
 124         </p><p>
 125             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glShadeModel</code>
 126             is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 127             and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 128         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 129             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SHADE_MODEL</code>
 130         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 131             <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>,
 132             <a class="citerefentry" href="glColor.xml"><span class="citerefentry"><span class="refentrytitle">glColor</span></span></a>,
 133             <a class="citerefentry" href="glLight.xml"><span class="citerefentry"><span class="refentrytitle">glLight</span></span></a>,
 134             <a class="citerefentry" href="glLightModel.xml"><span class="citerefentry"><span class="refentrytitle">glLightModel</span></span></a>
 135         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 136             Copyright <span class="trademark"></span>© 1991-2006
 137             Silicon Graphics, Inc. This document is licensed under the SGI
 138             Free Software B License. For details, see
 139             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 140         </p></div></div></body></html>