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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>glSelectBuffer</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glSelectBuffer"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glSelectBuffer — establish a buffer for selection mode values</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">glSelectBuffer</b>(</code></td><td>GLsizei </td><td><var class="pdparam">size</var>, </td></tr><tr><td> </td><td>GLuint * </td><td><var class="pdparam">buffer</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>size</code></em></span></dt><dd><p> | |
4 | Specifies the size of <em class="parameter"><code>buffer</code></em>. | |
5 | </p></dd><dt><span class="term"><em class="parameter"><code>buffer</code></em></span></dt><dd><p> | |
6 | Returns the selection data. | |
7 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
8 | <code class="function">glSelectBuffer</code> has two arguments: | |
9 | <em class="parameter"><code>buffer</code></em> is a pointer to an array of unsigned integers, | |
10 | and <em class="parameter"><code>size</code></em> indicates the size of the array. | |
11 | <em class="parameter"><code>buffer</code></em> returns values from the name stack | |
12 | (see <a class="citerefentry" href="glInitNames.xml"><span class="citerefentry"><span class="refentrytitle">glInitNames</span></span></a>, <a class="citerefentry" href="glLoadName.xml"><span class="citerefentry"><span class="refentrytitle">glLoadName</span></span></a>, <a class="citerefentry" href="glPushName.xml"><span class="citerefentry"><span class="refentrytitle">glPushName</span></span></a>) | |
13 | when the rendering mode is <code class="constant">GL_SELECT</code> (see <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a>). | |
14 | <code class="function">glSelectBuffer</code> must be issued before selection mode is enabled, | |
15 | and it must not be issued while the rendering mode is <code class="constant">GL_SELECT</code>. | |
16 | </p><p> | |
17 | A programmer can use selection to determine which primitives | |
18 | are drawn into some region of a window. | |
19 | The region is defined by the current modelview and perspective matrices. | |
20 | </p><p> | |
21 | In selection mode, no pixel fragments are produced from rasterization. | |
22 | Instead, | |
23 | if a primitive or a raster position intersects the clipping | |
24 | volume defined by the viewing frustum | |
25 | and the user-defined clipping planes, | |
26 | this primitive causes a selection hit. | |
27 | (With polygons, no hit occurs if the polygon is culled.) | |
28 | When a change is made to the name stack, | |
29 | or when <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> is called, | |
30 | a hit record is copied to <em class="parameter"><code>buffer</code></em> if any hits have occurred since the | |
31 | last such event | |
32 | (name stack change or | |
33 | <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> call). | |
34 | The hit record consists of the number of names in the name stack at the | |
35 | time of the event, followed by the minimum and maximum depth values | |
36 | of all vertices that hit since the previous event, | |
37 | followed by the name stack contents, | |
38 | bottom name first. | |
39 | </p><p> | |
40 | Depth values (which are in the range [0,1]) are multiplied by | |
41 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> | |
42 | ||
43 | <mml:mrow> | |
44 | <mml:msup><mml:mn>2</mml:mn> | |
45 | <mml:mn>32</mml:mn> | |
46 | </mml:msup> | |
47 | <mml:mo>-</mml:mo> | |
48 | <mml:mn>1</mml:mn> | |
49 | </mml:mrow> | |
50 | </mml:math>, | |
51 | before being placed in the hit record. | |
52 | </p><p> | |
53 | An internal index into <em class="parameter"><code>buffer</code></em> is reset to 0 whenever selection mode | |
54 | is entered. | |
55 | Each time a hit record is copied into <em class="parameter"><code>buffer</code></em>, | |
56 | the index is incremented to point to the cell just past the end | |
57 | of the block of names\(emthat is, to the next available cell | |
58 | If the hit record is larger than the number of remaining locations in <em class="parameter"><code>buffer</code></em>, | |
59 | as much data as can fit is copied, | |
60 | and the overflow flag is set. | |
61 | If the name stack is empty when a hit record is copied, | |
62 | that record consists of 0 followed by the minimum and maximum depth values. | |
63 | </p><p> | |
64 | To exit selection mode, call <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> with an argument | |
65 | other than <code class="constant">GL_SELECT</code>. | |
66 | Whenever <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> is called while the render mode is <code class="constant">GL_SELECT</code>, | |
67 | it returns the number of hit records copied to <em class="parameter"><code>buffer</code></em>, | |
68 | resets the overflow flag and the selection buffer pointer, | |
69 | and initializes the name stack to be empty. | |
70 | If the overflow bit was set when <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> was called, | |
71 | a negative hit record count is returned. | |
72 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> | |
73 | The contents of <em class="parameter"><code>buffer</code></em> is undefined until <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> is called | |
74 | with an argument other than <code class="constant">GL_SELECT</code>. | |
75 | </p><p> | |
76 | <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>/<a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a> primitives and calls to <a class="citerefentry" href="glRasterPos.xml"><span class="citerefentry"><span class="refentrytitle">glRasterPos</span></span></a> | |
77 | can result in hits. <a class="citerefentry" href="glWindowPos.xml"><span class="citerefentry"><span class="refentrytitle">glWindowPos</span></span></a> will always generate a selection hit. | |
78 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
79 | <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>size</code></em> is negative. | |
80 | </p><p> | |
81 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glSelectBuffer</code> is called while the | |
82 | render mode is <code class="constant">GL_SELECT</code>, | |
83 | or if <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> is called with argument <code class="constant">GL_SELECT</code> before | |
84 | <code class="function">glSelectBuffer</code> is called at least once. | |
85 | </p><p> | |
86 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glSelectBuffer</code> | |
87 | is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a> | |
88 | and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>. | |
89 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p> | |
90 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_NAME_STACK_DEPTH</code> | |
91 | </p><p> | |
92 | <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SELECTION_BUFFER_SIZE</code> | |
93 | </p><p> | |
94 | <a class="citerefentry" href="glGetPointerv.xml"><span class="citerefentry"><span class="refentrytitle">glGetPointerv</span></span></a> with argument <code class="constant">GL_SELECTION_BUFFER_POINTER</code> | |
95 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
96 | <a class="citerefentry" href="glFeedbackBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glFeedbackBuffer</span></span></a>, | |
97 | <a class="citerefentry" href="glInitNames.xml"><span class="citerefentry"><span class="refentrytitle">glInitNames</span></span></a>, | |
98 | <a class="citerefentry" href="glLoadName.xml"><span class="citerefentry"><span class="refentrytitle">glLoadName</span></span></a>, | |
99 | <a class="citerefentry" href="glPushName.xml"><span class="citerefentry"><span class="refentrytitle">glPushName</span></span></a>, | |
100 | <a class="citerefentry" href="glRenderMode.xml"><span class="citerefentry"><span class="refentrytitle">glRenderMode</span></span></a> | |
101 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
102 | Copyright <span class="trademark"></span>© 1991-2006 | |
103 | Silicon Graphics, Inc. This document is licensed under the SGI | |
104 | Free Software B License. For details, see | |
105 | <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. | |
106 | </p></div></div></body></html> |