upstream-man-pages/man2/xhtml/gluNurbsProperty.xml

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd">
   2 <!-- saved from url=(0013)about:internet -->
   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>gluNurbsProperty</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluNurbsProperty"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluNurbsProperty — set a NURBS property</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">gluNurbsProperty</b>(</code></td><td>GLUnurbs*  </td><td><var class="pdparam">nurb</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">property</var>, </td></tr><tr><td> </td><td>GLfloat  </td><td><var class="pdparam">value</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>nurb</code></em></span></dt><dd><p>
   4                     Specifies the NURBS object (created with <a class="citerefentry" href="gluNewNurbsRenderer.xml"><span class="citerefentry"><span class="refentrytitle">gluNewNurbsRenderer</span></span></a>).
   5                 </p></dd><dt><span class="term"><em class="parameter"><code>property</code></em></span></dt><dd><p>
   6                     Specifies the property to be set. Valid values are
   7                     <code class="constant">GLU_SAMPLING_TOLERANCE</code>,
   8                     <code class="constant">GLU_DISPLAY_MODE</code>,
   9                     <code class="constant">GLU_CULLING</code>,
  10                     <code class="constant">GLU_AUTO_LOAD_MATRIX</code>,
  11                     <code class="constant">GLU_PARAMETRIC_TOLERANCE</code>,
  12                     <code class="constant">GLU_SAMPLING_METHOD</code>,
  13                     <code class="constant">GLU_U_STEP</code>,
  14                     <code class="constant">GLU_V_STEP</code>, or
  15                     <code class="constant">GLU_NURBS_MODE</code>.
  16                 </p></dd><dt><span class="term"><em class="parameter"><code>value</code></em></span></dt><dd><p>
  17                     Specifies the value of the indicated property.
  18                     It may be a numeric value or one of
  19                     <code class="constant">GLU_OUTLINE_POLYGON</code>,
  20                     <code class="constant">GLU_FILL</code>,
  21                     <code class="constant">GLU_OUTLINE_PATCH</code>,
  22                     <code class="constant">GLU_TRUE</code>,
  23                     <code class="constant">GLU_FALSE</code>,
  24                     <code class="constant">GLU_PATH_LENGTH</code>,
  25                     <code class="constant">GLU_PARAMETRIC_ERROR</code>,
  26                     <code class="constant">GLU_DOMAIN_DISTANCE</code>,
  27                     <code class="constant">GLU_NURBS_RENDERER</code>, or
  28                     <code class="constant">GLU_NURBS_TESSELLATOR</code>.
  29                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  30             <code class="function">gluNurbsProperty</code> is used to control properties stored in a NURBS object. These
  31             properties affect the way that a NURBS curve is rendered. The accepted
  32             values for <em class="parameter"><code>property</code></em> are as follows:
  33         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLU_NURBS_MODE</code></span></dt><dd><p>
  34                         <em class="parameter"><code>value</code></em> should be set to be either <code class="constant">GLU_NURBS_RENDERER</code> or
  35                         <code class="constant">GLU_NURBS_TESSELLATOR</code>. When set to <code class="constant">GLU_NURBS_RENDERER</code>, NURBS objects
  36                         are tessellated into OpenGL primitives and sent to the pipeline for
  37                         rendering. When set to <code class="constant">GLU_NURBS_TESSELLATOR</code>, NURBS objects are
  38                         tessellated into OpenGL primitives but the vertices, normals, colors, and/or textures are
  39                         retrieved back through a callback interface (see <a class="citerefentry" href="gluNurbsCallback.xml"><span class="citerefentry"><span class="refentrytitle">gluNurbsCallback</span></span></a>). This allows the user to cache the
  40                         tessellated results for further processing.
  41                         The initial value is <code class="constant">GLU_NURBS_RENDERER</code>.
  42                     </p></dd><dt><span class="term"><code class="constant">GLU_SAMPLING_METHOD</code> </span></dt><dd><p>
  43                         Specifies how a NURBS surface should be
  44                         tessellated.
  45                         <em class="parameter"><code>value</code></em> may be one of <code class="constant">GLU_PATH_LENGTH</code>,
  46                         <code class="constant">GLU_PARAMETRIC_ERROR</code>,  <code class="constant">GLU_DOMAIN_DISTANCE</code>,
  47                         <code class="constant">GLU_OBJECT_PATH_LENGTH</code>, or
  48                         <code class="constant">GLU_OBJECT_PARAMETRIC_ERROR</code>.
  49                         When set to <code class="constant">GLU_PATH_LENGTH</code>, the surface is rendered so that
  50                         the maximum length, in
  51                         pixels, of the edges of the tessellation polygons is no greater than
  52                         what is specified by <code class="constant">GLU_SAMPLING_TOLERANCE</code>.
  53                     </p><p>
  54                         <code class="constant">GLU_PARAMETRIC_ERROR</code> specifies that the surface is rendered in such a
  55                         way that the value specified by <code class="constant">GLU_PARAMETRIC_TOLERANCE</code> describes the
  56                         maximum distance, in pixels, between the tessellation polygons and the
  57                         surfaces they approximate.
  58                     </p><p>
  59                         <code class="constant">GLU_DOMAIN_DISTANCE</code> allows users to specify, in parametric coordinates,
  60                         how many sample points per unit length are taken in <span class="emphasis"><em>u</em></span>, <span class="emphasis"><em>v</em></span>
  61                         direction.
  62                     </p><p>
  63                         <code class="constant">GLU_OBJECT_PATH_LENGTH</code>  is similar to <code class="constant">GLU_PATH_LENGTH</code>
  64                         except that it is view independent; that is, the surface is rendered so that the maximum length, in object space, of edges of the tessellation polygons is no greater than what is specified by <code class="constant">GLU_SAMPLING_TOLERANCE</code>.
  65                     </p><p>
  66                         <code class="constant">GLU_OBJECT_PARAMETRIC_ERROR</code> is similar to  <code class="constant">GLU_PARAMETRIC_ERROR</code> except that it is view independent; that is, the surface is rendered in such a way that the value specified by <code class="constant">GLU_PARAMETRIC_TOLERANCE</code> describes the maximum distance, in object space, between the tessellation polygons and the surfaces they approximate.
  67                     </p><p>
  68                         The initial value of <code class="constant">GLU_SAMPLING_METHOD</code> is <code class="constant">GLU_PATH_LENGTH</code>.
  69                     </p></dd><dt><span class="term"><code class="constant">GLU_SAMPLING_TOLERANCE</code></span></dt><dd><p>
  70                         Specifies the maximum length, in pixels or in object space length unit,
  71                         to use when the sampling method is set to <code class="constant">GLU_PATH_LENGTH</code> or
  72                         <code class="constant">GLU_OBJECT_PATH_LENGTH</code>.
  73                         The NURBS code is conservative when rendering a curve
  74                         or surface, so the actual length can be somewhat shorter. The initial
  75                         value is 50.0 pixels.
  76                     </p></dd><dt><span class="term"><code class="constant">GLU_PARAMETRIC_TOLERANCE</code></span></dt><dd><p>
  77                         Specifies the maximum distance, in pixels or in object space length unit,
  78                         to use when the sampling method is <code class="constant">GLU_PARAMETRIC_ERROR</code> or
  79                         <code class="constant">GLU_OBJECT_PARAMETRIC_ERROR</code>.
  80                         The initial value is 0.5.
  81                     </p></dd><dt><span class="term"><code class="constant">GLU_U_STEP</code></span></dt><dd><p>
  82                         Specifies the number of sample points per unit length taken
  83                         along the <span class="emphasis"><em>u</em></span> axis in parametric coordinates. It is needed when
  84                         <code class="constant">GLU_SAMPLING_METHOD</code> is set to <code class="constant">GLU_DOMAIN_DISTANCE</code>.
  85                         The initial value is 100.
  86                     </p></dd><dt><span class="term"><code class="constant">GLU_V_STEP</code></span></dt><dd><p>
  87                         Specifies the number of sample points per unit length taken
  88                         along the <span class="emphasis"><em>v</em></span> axis in parametric coordinate. It is needed when
  89                         <code class="constant">GLU_SAMPLING_METHOD</code> is set to <code class="constant">GLU_DOMAIN_DISTANCE</code>. The initial
  90                         value is 100.
  91                     </p></dd><dt><span class="term"><code class="constant">GLU_DISPLAY_MODE</code></span></dt><dd><p>
  92                         <em class="parameter"><code>value</code></em> can be set to
  93                         <code class="constant">GLU_OUTLINE_POLYGON</code>, <code class="constant">GLU_FILL</code>, or
  94                         <code class="constant">GLU_OUTLINE_PATCH</code>.
  95                         When <code class="constant">GLU_NURBS_MODE</code> is set to be <code class="constant">GLU_NURBS_RENDERER</code>,
  96                         <em class="parameter"><code>value</code></em> defines how a NURBS surface should be rendered.
  97                         When <em class="parameter"><code>value</code></em> is set to <code class="constant">GLU_FILL</code>, the surface is rendered as a
  98                         set of polygons. When <em class="parameter"><code>value</code></em> is set to
  99                         <code class="constant">GLU_OUTLINE_POLYGON</code>, the NURBS library draws only the outlines
 100                         of the polygons created by tessellation. When <em class="parameter"><code>value</code></em> is set to
 101                         <code class="constant">GLU_OUTLINE_PATCH</code> just the outlines of patches and trim
 102                         curves defined by the user are drawn.
 103                     </p><p>
 104                         When <code class="constant">GLU_NURBS_MODE</code> is set to be <code class="constant">GLU_NURBS_TESSELLATOR</code>,
 105                         <em class="parameter"><code>value</code></em> defines how a NURBS surface should be tessellated.
 106                         When <code class="constant">GLU_DISPLAY_MODE</code> is set to <code class="constant">GLU_FILL</code> or
 107                         <code class="constant">GLU_OUTLINE_POLYGON</code>,
 108                         the NURBS surface is tessellated into OpenGL triangle primitives that can be
 109                         retrieved back  through callback functions. If <code class="constant">GLU_DISPLAY_MODE</code> is set to
 110                         <code class="constant">GLU_OUTLINE_PATCH</code>, only the outlines of the patches and trim curves are generated as a sequence of line strips that can be retrieved back through callback functions.
 111                     </p><p>
 112                         The initial value is <code class="constant">GLU_FILL</code>.
 113                     </p></dd><dt><span class="term"><code class="constant">GLU_CULLING</code></span></dt><dd><p>
 114                         <em class="parameter"><code>value</code></em> is a boolean value that, when set to <code class="constant">GLU_TRUE</code>, indicates that
 115                         a NURBS curve should be discarded prior to tessellation if its control points
 116                         lie outside the current viewport. The initial value is <code class="constant">GLU_FALSE</code>.
 117                     </p></dd><dt><span class="term"><code class="constant">GLU_AUTO_LOAD_MATRIX</code></span></dt><dd><p>
 118                         <em class="parameter"><code>value</code></em> is a boolean value. When set to <code class="constant">GLU_TRUE</code>, the NURBS code
 119                         downloads the projection matrix, the modelview matrix, and the
 120                         viewport from the GL server to compute sampling and
 121                         culling
 122                         matrices for each NURBS curve that is rendered. Sampling and culling matrices
 123                         are required to determine the tessellation of a NURBS surface into line segments
 124                         or polygons and to cull a NURBS surface if it lies outside the viewport.
 125                     </p><p>
 126                         If this mode is set to <code class="constant">GLU_FALSE</code>, then the program needs
 127                         to provide a projection matrix, a modelview matrix, and a viewport
 128                         for the NURBS renderer to use to construct sampling and culling matrices.
 129                         This can be done with the <a class="citerefentry" href="gluLoadSamplingMatrices.xml"><span class="citerefentry"><span class="refentrytitle">gluLoadSamplingMatrices</span></span></a> function.
 130                         This mode is initially set to <code class="constant">GLU_TRUE</code>.
 131                         Changing it from <code class="constant">GLU_TRUE</code> to <code class="constant">GLU_FALSE</code> does not affect
 132                         the sampling and culling matrices until
 133                         <a class="citerefentry" href="gluLoadSamplingMatrices.xml"><span class="citerefentry"><span class="refentrytitle">gluLoadSamplingMatrices</span></span></a>
 134                         is called.
 135                     </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
 136             If <code class="constant">GLU_AUTO_LOAD_MATRIX</code> is true, sampling and culling may be
 137             executed incorrectly if NURBS routines are compiled into a display list.
 138         </p><p>
 139             A <em class="parameter"><code>property</code></em> of
 140             <code class="constant">GLU_PARAMETRIC_TOLERANCE</code>,
 141             <code class="constant">GLU_SAMPLING_METHOD</code>,
 142             <code class="constant">GLU_U_STEP</code>, or
 143             <code class="constant">GLU_V_STEP</code>,
 144             or a <em class="parameter"><code>value</code></em> of
 145             <code class="constant">GLU_PATH_LENGTH</code>,
 146             <code class="constant">GLU_PARAMETRIC_ERROR</code>,
 147             <code class="constant">GLU_DOMAIN_DISTANCE</code>
 148             are only available if the GLU version is 1.1 or greater. They are not
 149             valid parameters in GLU 1.0.
 150         </p><p>
 151             <a class="citerefentry" href="gluGetString.xml"><span class="citerefentry"><span class="refentrytitle">gluGetString</span></span></a> can
 152             be used to determine the GLU version.
 153         </p><p>
 154             <code class="constant">GLU_NURBS_MODE</code> is only available if the GLU version is 1.3 or
 155             greater.
 156         </p><p>
 157             The <code class="constant">GLU_OBJECT_PATH_LENGTH</code> and <code class="constant">GLU_OBJECT_PARAMETRIC_ERROR</code>
 158             values for the <code class="constant">GLU_SAMPLING_METHOD</code> property are only available if
 159             the GLU version is 1.3 or greater.
 160         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 161             <a class="citerefentry" href="gluGetNurbsProperty.xml"><span class="citerefentry"><span class="refentrytitle">gluGetNurbsProperty</span></span></a>,
 162             <a class="citerefentry" href="gluGetString.xml"><span class="citerefentry"><span class="refentrytitle">gluGetString</span></span></a>,
 163             <a class="citerefentry" href="gluLoadSamplingMatrices.xml"><span class="citerefentry"><span class="refentrytitle">gluLoadSamplingMatrices</span></span></a>,
 164             <a class="citerefentry" href="gluNewNurbsRenderer.xml"><span class="citerefentry"><span class="refentrytitle">gluNewNurbsRenderer</span></span></a>,
 165             <a class="citerefentry" href="gluNurbsCallback.xml"><span class="citerefentry"><span class="refentrytitle">gluNurbsCallback</span></span></a>
 166         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 167             Copyright <span class="trademark"></span>© 1991-2006
 168             Silicon Graphics, Inc. This document is licensed under the SGI
 169             Free Software B License. For details, see
 170             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 171         </p></div></div></body></html>