| 1 | <?xml version="1.0" encoding="UTF-8"?> |
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| 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>glMultiDrawArraysIndirect - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glMultiDrawArraysIndirect"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glMultiDrawArraysIndirect — render multiple sets of primitives from array data, taking parameters from memory</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">glMultiDrawArraysIndirect</b>(</code></td><td>GLenum </td><td><var class="pdparam">mode</var>, </td></tr><tr><td> </td><td>const void * </td><td><var class="pdparam">indirect</var>, </td></tr><tr><td> </td><td>GLsizei </td><td><var class="pdparam">drawcount</var>, </td></tr><tr><td> </td><td>GLsizei </td><td><var class="pdparam">stride</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>mode</code></em></span></dt><dd><p> |
| 5 | Specifies what kind of primitives to render. |
| 6 | Symbolic constants |
| 7 | <code class="constant">GL_POINTS</code>, |
| 8 | <code class="constant">GL_LINE_STRIP</code>, |
| 9 | <code class="constant">GL_LINE_LOOP</code>, |
| 10 | <code class="constant">GL_LINES</code>, |
| 11 | <code class="constant">GL_LINE_STRIP_ADJACENCY</code>, |
| 12 | <code class="constant">GL_LINES_ADJACENCY</code>, |
| 13 | <code class="constant">GL_TRIANGLE_STRIP</code>, |
| 14 | <code class="constant">GL_TRIANGLE_FAN</code>, |
| 15 | <code class="constant">GL_TRIANGLES</code>, |
| 16 | <code class="constant">GL_TRIANGLE_STRIP_ADJACENCY</code>, |
| 17 | <code class="constant">GL_TRIANGLES_ADJACENCY</code>, and |
| 18 | <code class="constant">GL_PATCHES</code> |
| 19 | are accepted. |
| 20 | </p></dd><dt><span class="term"><em class="parameter"><code>indirect</code></em></span></dt><dd><p> |
| 21 | Specifies the address of an array of structures containing the draw parameters. |
| 22 | </p></dd><dt><span class="term"><em class="parameter"><code>drawcount</code></em></span></dt><dd><p> |
| 23 | Specifies the the number of elements in the array of draw parameter structures. |
| 24 | </p></dd><dt><span class="term"><em class="parameter"><code>stride</code></em></span></dt><dd><p> |
| 25 | Specifies the distance in basic machine units between elements of the draw parameter array. |
| 26 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> |
| 27 | <code class="function">glMultiDrawArraysIndirect</code> specifies multiple geometric primitives |
| 28 | with very few subroutine calls. <code class="function">glMultiDrawArraysIndirect</code> behaves |
| 29 | similarly to a multitude of calls to <a href="glDrawArraysInstancedBaseInstance.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstancedBaseInstance</span></span></a>, |
| 30 | execept that the parameters to each call to <a href="glDrawArraysInstancedBaseInstance.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstancedBaseInstance</span></span></a> |
| 31 | are stored in an array in memory at the address given by <em class="parameter"><code>indirect</code></em>, separated |
| 32 | by the stride, in basic machine units, specified by <em class="parameter"><code>stride</code></em>. If <em class="parameter"><code>stride</code></em> |
| 33 | is zero, then the array is assumed to be tightly packed in memory. |
| 34 | </p><p> |
| 35 | The parameters addressed by <em class="parameter"><code>indirect</code></em> are packed into an array of structures, |
| 36 | each element of which takes the form (in C): |
| 37 | </p><pre class="programlisting"> typedef struct { |
| 38 | uint count; |
| 39 | uint primCount; |
| 40 | uint first; |
| 41 | uint baseInstance; |
| 42 | } DrawArraysIndirectCommand;</pre><p> |
| 43 | </p><p> |
| 44 | A single call to <code class="function">glMultiDrawArraysIndirect</code> is equivalent, assuming no errors |
| 45 | are generated to: |
| 46 | </p><pre class="programlisting"> GLsizei n; |
| 47 | for (n = 0; n < drawcount; n++) |
| 48 | { |
| 49 | const DrawArraysIndirectCommand *cmd; |
| 50 | if (stride != 0) |
| 51 | { |
| 52 | cmd = (const DrawArraysIndirectCommand *)((uintptr)indirect + n * stride); |
| 53 | } |
| 54 | else |
| 55 | { |
| 56 | cmd = (const DrawArraysIndirectCommand *)indirect + n; |
| 57 | } |
| 58 | |
| 59 | glDrawArraysInstancedBaseInstance(mode, cmd->first, cmd->count, cmd->primCount, cmd->baseInstance); |
| 60 | }</pre><p> |
| 61 | </p><p> |
| 62 | If a buffer is bound to the <code class="constant">GL_DRAW_INDIRECT_BUFFER</code> binding at the time |
| 63 | of a call to <code class="function">glMultiDrawArraysIndirect</code>, <em class="parameter"><code>indirect</code></em> |
| 64 | is interpreted as an offset, in basic machine units, into that buffer and the parameter |
| 65 | data is read from the buffer rather than from client memory. |
| 66 | </p><p> |
| 67 | In contrast to <a href="glDrawArraysInstancedBaseInstance.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstancedBaseInstance</span></span></a>, |
| 68 | the <code class="code">first</code> member of the parameter structure is unsigned, and out-of-range indices |
| 69 | do not generate an error. |
| 70 | </p><p> |
| 71 | Vertex attributes that are modified by <code class="function">glMultiDrawArraysIndirect</code> have an |
| 72 | unspecified value after <code class="function">glMultiDrawArraysIndirect</code> returns. Attributes that aren't |
| 73 | modified remain well defined. |
| 74 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> |
| 75 | The <em class="parameter"><code>baseInstance</code></em> member of the <em class="parameter"><code>DrawArraysIndirectCommand</code></em> |
| 76 | structure is defined only if the GL version is 4.2 or greater. For versions of the GL less than 4.2, |
| 77 | this parameter is present but is reserved and should be set to zero. On earlier versions of the GL, |
| 78 | behavior is undefined if it is non-zero. |
| 79 | </p><p> |
| 80 | <code class="function">glMultiDrawArraysIndirect</code> is available only if the GL version is 4.3 or greater. |
| 81 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> |
| 82 | <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>mode</code></em> is not an accepted value. |
| 83 | </p><p> |
| 84 | <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>stride</code></em> is not a multiple |
| 85 | of four. |
| 86 | </p><p> |
| 87 | <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>drawcount</code></em> is negative. |
| 88 | </p><p> |
| 89 | <code class="constant">GL_INVALID_OPERATION</code> is generated if a non-zero buffer object name is bound to an |
| 90 | enabled array or to the <code class="constant">GL_DRAW_INDIRECT_BUFFER</code> binding and the buffer object's data store is currently mapped. |
| 91 | </p><p> |
| 92 | <code class="constant">GL_INVALID_OPERATION</code> is generated if a geometry shader is active and <em class="parameter"><code>mode</code></em> |
| 93 | is incompatible with the input primitive type of the geometry shader in the currently installed program object. |
| 94 | </p><p> |
| 95 | <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>mode</code></em> is <code class="constant">GL_PATCHES</code> |
| 96 | and no tessellation control shader is active. |
| 97 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> |
| 98 | <a href="glDrawArrays.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArrays</span></span></a>, |
| 99 | <a href="glDrawArraysInstanced.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArraysInstanced</span></span></a>, |
| 100 | <a href="glDrawElements.xml"><span class="citerefentry"><span class="refentrytitle">glDrawElements</span></span></a>, |
| 101 | <a href="glDrawRangeElements.xml"><span class="citerefentry"><span class="refentrytitle">glDrawRangeElements</span></span></a>, |
| 102 | <a href="glDrawArraysIndirect.xml"><span class="citerefentry"><span class="refentrytitle">glDrawArraysIndirect</span></span></a>, |
| 103 | <a href="glMultiDrawElementsIndirect.xml"><span class="citerefentry"><span class="refentrytitle">glMultiDrawElementsIndirect</span></span></a> |
| 104 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> |
| 105 | Copyright <span class="trademark"></span>© 2012 Khronos Group. |
| 106 | This material may be distributed subject to the terms and conditions set forth in |
| 107 | the Open Publication License, v 1.0, 8 June 1999. |
| 108 | <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>. |
| 109 | </p></div></div></body></html> |