upstream-man-pages/man2/glClipPlane.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glClipPlane">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glClipPlane</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glClipPlane</refname>
  17         <refpurpose>specify a plane against which all geometry is clipped</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glClipPlane</function></funcdef>
  23                 <paramdef>GLenum <parameter>plane</parameter></paramdef>
  24                 <paramdef>const GLdouble * <parameter>equation</parameter></paramdef>
  25             </funcprototype>
  26         </funcsynopsis>
  27     </refsynopsisdiv>
  28     <!-- eqn: ignoring delim $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>plane</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specifies which clipping plane is being positioned.
  36                     Symbolic names of the form <constant>GL_CLIP_PLANE</constant><emphasis>i</emphasis>,
  37                     where <emphasis>i</emphasis> is an integer between 0 and <constant>GL_MAX_CLIP_PLANES</constant>
  38                     <inlineequation><mml:math>
  39                         <!-- eqn: - 1:-->
  40                         <mml:mn>-1</mml:mn>
  41                     </mml:math></inlineequation>,
  42                     are accepted.
  43                 </para>
  44             </listitem>
  45         </varlistentry>
  46         <varlistentry>
  47             <term><parameter>equation</parameter></term>
  48             <listitem>
  49                 <para>
  50                     Specifies the address of an array of four double-precision floating-point values.
  51                     These values are interpreted as a plane equation.
  52                 </para>
  53             </listitem>
  54         </varlistentry>
  55         </variablelist>
  56     </refsect1>
  57     <refsect1 id="description"><title>Description</title>
  58         <para>
  59             Geometry is always clipped against the boundaries of a six-plane frustum
  60             in <emphasis>x</emphasis>, <emphasis>y</emphasis>, and <emphasis>z</emphasis>.
  61             <function>glClipPlane</function> allows the specification of additional planes,
  62             not necessarily perpendicular to the <emphasis>x</emphasis>, <emphasis>y</emphasis>, or <emphasis>z</emphasis> axis,
  63             against which all geometry is clipped.
  64             To determine the maximum number of additional clipping planes, call
  65             <citerefentry><refentrytitle>glGetIntegerv</refentrytitle></citerefentry> with argument <constant>GL_MAX_CLIP_PLANES</constant>. All
  66             implementations support at least six such clipping planes.
  67             Because the resulting clipping region is the intersection
  68             of the defined half-spaces,
  69             it is always convex.
  70         </para>
  71         <para>
  72             <function>glClipPlane</function> specifies a half-space using a four-component plane equation.
  73             When <function>glClipPlane</function> is called,
  74             <parameter>equation</parameter> is transformed by the inverse of the modelview matrix
  75             and stored in the resulting eye coordinates.
  76             Subsequent changes to the modelview matrix have no effect on the
  77             stored plane-equation components.
  78             If the dot product of the eye coordinates of a vertex with the
  79             stored plane equation components is positive or zero,
  80             the vertex is <emphasis>in</emphasis> with respect to that clipping plane.
  81             Otherwise, it is <emphasis>out</emphasis>.
  82         </para>
  83         <para>
  84             To enable and disable clipping planes, call
  85             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with the argument
  86             <constant>GL_CLIP_PLANE</constant><emphasis>i</emphasis>,
  87             where <emphasis>i</emphasis> is the plane number.
  88         </para>
  89         <para>
  90             All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates
  91             and are
  92             disabled.
  93         </para>
  94     </refsect1>
  95     <refsect1 id="notes"><title>Notes</title>
  96         <para>
  97             It is always the case that <constant>GL_CLIP_PLANE</constant>
  98             <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
  99             = <constant>GL_CLIP_PLANE0</constant> +
 100             <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>.
 101         </para>
 102     </refsect1>
 103     <refsect1 id="errors"><title>Errors</title>
 104         <para>
 105             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>plane</parameter> is not an accepted value.
 106         </para>
 107         <para>
 108             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glClipPlane</function>
 109             is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
 110             and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
 111         </para>
 112     </refsect1>
 113     <refsect1 id="associatedgets"><title>Associated Gets</title>
 114         <para>
 115             <citerefentry><refentrytitle>glGetClipPlane</refentrytitle></citerefentry>
 116         </para>
 117         <para>
 118             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_CLIP_PLANE</constant><emphasis>i</emphasis>
 119         </para>
 120     </refsect1>
 121     <refsect1 id="seealso"><title>See Also</title>
 122         <para>
 123             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>
 124         </para>
 125     </refsect1>
 126     <refsect1 id="Copyright"><title>Copyright</title>
 127         <para>
 128             Copyright <trademark class="copyright"></trademark> 1991-2006
 129             Silicon Graphics, Inc. This document is licensed under the SGI
 130             Free Software B License. For details, see
 131             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 132         </para>
 133     </refsect1>
 134 </refentry>