HCoop / clinton / guile-figl.git / blame
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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>gluPickMatrix</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluPickMatrix"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluPickMatrix — define a picking region</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">gluPickMatrix</b>(</code></td><td>GLdouble </td><td><var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLdouble </td><td><var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLdouble </td><td><var class="pdparam">delX</var>, </td></tr><tr><td> </td><td>GLdouble </td><td><var class="pdparam">delY</var>, </td></tr><tr><td> </td><td>GLint * </td><td><var class="pdparam">viewport</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>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p> | |
| 4 | Specify the center of a picking region in window coordinates. | |
| 5 | </p></dd><dt><span class="term"><em class="parameter"><code>delX</code></em>, </span><span class="term"><em class="parameter"><code>delY</code></em></span></dt><dd><p> | |
| 6 | Specify the width and height, respectively, of the picking region in window | |
| 7 | coordinates. | |
| 8 | </p></dd><dt><span class="term"><em class="parameter"><code>viewport</code></em></span></dt><dd><p> | |
| 9 | Specifies the current viewport (as from a <a class="citerefentry" href="glGetIntegerv.xml"><span class="citerefentry"><span class="refentrytitle">glGetIntegerv</span></span></a> call). | |
| 10 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
| 11 | <code class="function">gluPickMatrix</code> creates a projection matrix that can be used to restrict drawing | |
| 12 | to a small region of the viewport. | |
| 13 | This is typically useful to | |
| 14 | determine what objects are being drawn near the cursor. | |
| 15 | Use <code class="function">gluPickMatrix</code> to | |
| 16 | restrict drawing to a small region around the cursor. | |
| 17 | Then, | |
| 18 | enter selection mode (with <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a>) and rerender the scene. | |
| 19 | All primitives that would have been drawn near | |
| 20 | the cursor are identified and stored in the selection buffer. | |
| 21 | </p><p> | |
| 22 | The matrix created by <code class="function">gluPickMatrix</code> is multiplied by the current matrix just | |
| 23 | as if <a class="citerefentry" href="glMultMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glMultMatrix</span></span></a> is called with the generated matrix. | |
| 24 | To effectively use the generated pick matrix for picking, | |
| 25 | first call <a class="citerefentry" href="glLoadIdentity.xml"><span class="citerefentry"><span class="refentrytitle">glLoadIdentity</span></span></a> to load an identity matrix onto the | |
| 26 | perspective matrix stack. | |
| 27 | Then call <code class="function">gluPickMatrix</code>, | |
| 28 | and, finally, call a command (such as <a class="citerefentry" href="gluPerspective.xml"><span class="citerefentry"><span class="refentrytitle">gluPerspective</span></span></a>) | |
| 29 | to multiply the perspective matrix by the pick matrix. | |
| 30 | </p><p> | |
| 31 | When using <code class="function">gluPickMatrix</code> to pick NURBS, be careful to turn off the NURBS | |
| 32 | property | |
| 33 | <code class="constant">GLU_AUTO_LOAD_MATRIX</code>. If <code class="constant">GLU_AUTO_LOAD_MATRIX</code> is not | |
| 34 | turned off, then any NURBS surface rendered is subdivided differently with | |
| 35 | the pick matrix than the way it was subdivided without the pick matrix. | |
| 36 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="example"></a><h2>Example</h2><p> | |
| 37 | When rendering a scene as follows: | |
| 38 | </p><pre class="programlisting"> | |
| 39 | glMatrixMode(GL_PROJECTION); | |
| 40 | glLoadIdentity(); | |
| 41 | gluPerspective(...); | |
| 42 | glMatrixMode(GL_MODELVIEW); | |
| 43 | /* Draw the scene */ | |
| 44 | </pre><p> | |
| 45 | a portion of the viewport can be selected as a pick region like this: | |
| 46 | </p><pre class="programlisting"> | |
| 47 | glMatrixMode(GL_PROJECTION); | |
| 48 | glLoadIdentity(); | |
| 49 | gluPickMatrix(x, y, width, height, viewport); | |
| 50 | gluPerspective(...); | |
| 51 | glMatrixMode(GL_MODELVIEW); | |
| 52 | /* Draw the scene */ | |
| 53 | </pre><p> | |
| 54 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
| 55 | <a class="citerefentry" href="gluPerspective.xml"><span class="citerefentry"><span class="refentrytitle">gluPerspective</span></span></a>, | |
| 56 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a>, | |
| 57 | <a class="citerefentry" href="glLoadIdentity.xml"><span class="citerefentry"><span class="refentrytitle">glLoadIdentity</span></span></a>, | |
| 58 | <a class="citerefentry" href="glMultMatrix.xml"><span class="citerefentry"><span class="refentrytitle">glMultMatrix</span></span></a>, | |
| 59 | <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> | |
| 60 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
| 61 | Copyright <span class="trademark"></span>© 1991-2006 | |
| 62 | Silicon Graphics, Inc. This document is licensed under the SGI | |
| 63 | Free Software B License. For details, see | |
| 64 | <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. | |
| 65 | </p></div></div></body></html> |