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1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> | |
3 | <!-- saved from url=(0013)about:internet --> | |
4 | <?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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glClear</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glClear"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glClear — clear buffers to preset values</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glClear</b>(</code>GLbitfield <var class="pdparam">mask</var><code>)</code>;</p></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>mask</code></em></span></dt><dd><p> | |
5 | Bitwise OR of masks that indicate the buffers to be cleared. | |
6 | The three masks are | |
7 | <code class="constant">GL_COLOR_BUFFER_BIT</code>, | |
8 | <code class="constant">GL_DEPTH_BUFFER_BIT</code>, and | |
9 | <code class="constant">GL_STENCIL_BUFFER_BIT</code>. | |
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">glClear</code> sets the bitplane area of the window to values previously selected | |
12 | by <code class="function">glClearColor</code>, <code class="function">glClearDepth</code>, and | |
13 | <code class="function">glClearStencil</code>. | |
14 | Multiple color buffers can be cleared simultaneously by selecting | |
15 | more than one buffer at a time using <a href="glDrawBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>. | |
16 | </p><p> | |
17 | The pixel ownership test, | |
18 | the scissor test, | |
19 | dithering, and the buffer writemasks affect the operation of <code class="function">glClear</code>. | |
20 | The scissor box bounds the cleared region. | |
21 | Alpha function, | |
22 | blend function, | |
23 | logical operation, | |
24 | stenciling, | |
25 | texture mapping, | |
26 | and depth-buffering are ignored by <code class="function">glClear</code>. | |
27 | </p><p> | |
28 | <code class="function">glClear</code> takes a single argument that is the bitwise OR of several | |
29 | values indicating which buffer is to be cleared. | |
30 | </p><p> | |
31 | The values are as follows: | |
32 | </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_COLOR_BUFFER_BIT</code></span></dt><dd><p> | |
33 | Indicates the buffers currently enabled for color | |
34 | writing. | |
35 | </p></dd><dt><span class="term"><code class="constant">GL_DEPTH_BUFFER_BIT</code></span></dt><dd><p> | |
36 | Indicates the depth buffer. | |
37 | </p></dd><dt><span class="term"><code class="constant">GL_STENCIL_BUFFER_BIT</code></span></dt><dd><p> | |
38 | Indicates the stencil buffer. | |
39 | </p></dd></dl></div><p> | |
40 | The value to which each buffer is cleared depends on the setting of the | |
41 | clear value for that buffer. | |
42 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> | |
43 | If a buffer is not present, | |
44 | then a <code class="function">glClear</code> directed at that buffer has no effect. | |
45 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
46 | <code class="constant">GL_INVALID_VALUE</code> is generated if any bit other than the three defined | |
47 | bits is set in <em class="parameter"><code>mask</code></em>. | |
48 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p> | |
49 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_DEPTH_CLEAR_VALUE</code> | |
50 | </p><p> | |
51 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_COLOR_CLEAR_VALUE</code> | |
52 | </p><p> | |
53 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_STENCIL_CLEAR_VALUE</code> | |
54 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
55 | <code class="function">glClearColor</code>, | |
56 | <code class="function">glClearDepth</code>, | |
57 | <code class="function">glClearStencil</code>, | |
58 | <a href="glColorMask.xml"><span class="citerefentry"><span class="refentrytitle">glColorMask</span></span></a>, | |
59 | <a href="glDepthMask.xml"><span class="citerefentry"><span class="refentrytitle">glDepthMask</span></span></a>, | |
60 | <a href="glDrawBuffer.xml"><span class="citerefentry"><span class="refentrytitle">glDrawBuffer</span></span></a>, | |
61 | <a href="glScissor.xml"><span class="citerefentry"><span class="refentrytitle">glScissor</span></span></a>, | |
62 | <a href="glStencilMask.xml"><span class="citerefentry"><span class="refentrytitle">glStencilMask</span></span></a> | |
63 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
64 | Copyright <span class="trademark"></span>© 1991-2006 | |
65 | Silicon Graphics, Inc. This document is licensed under the SGI | |
66 | Free Software B License. For details, see | |
67 | <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. | |
68 | </p></div></div></body></html> |