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GLMULTIDRAWARRAYSIND(3G)	 OpenGL Manual	      GLMULTIDRAWARRAYSIND(3G)

NAME
       glMultiDrawArraysIndirect - render multiple sets of primitives from
       array data, taking parameters from memory

C SPECIFICATION
       void glMultiDrawArraysIndirect(GLenum mode, const void *indirect,
				      GLsizei drawcount, GLsizei stride);

PARAMETERS
       mode
	   Specifies what kind of primitives to render. Symbolic constants
	   GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES,
	   GL_LINE_STRIP_ADJACENCY, GL_LINES_ADJACENCY, GL_TRIANGLE_STRIP,
	   GL_TRIANGLE_FAN, GL_TRIANGLES, GL_TRIANGLE_STRIP_ADJACENCY,
	   GL_TRIANGLES_ADJACENCY, and GL_PATCHES are accepted.

       indirect
	   Specifies the address of an array of structures containing the draw
	   parameters.

       drawcount
	   Specifies the the number of elements in the array of draw parameter
	   structures.

       stride
	   Specifies the distance in basic machine units between elements of
	   the draw parameter array.

DESCRIPTION
       glMultiDrawArraysIndirect specifies multiple geometric primitives with
       very few subroutine calls.  glMultiDrawArraysIndirect behaves similarly
       to a multitude of calls to glDrawArraysInstancedBaseInstance(), execept
       that the parameters to each call to glDrawArraysInstancedBaseInstance()
       are stored in an array in memory at the address given by indirect,
       separated by the stride, in basic machine units, specified by stride.
       If stride is zero, then the array is assumed to be tightly packed in
       memory.

       The parameters addressed by indirect are packed into an array of
       structures, each element of which takes the form (in C):

	       typedef	struct {
		   uint	 count;
		   uint	 primCount;
		   uint	 first;
		   uint	 baseInstance;
	       } DrawArraysIndirectCommand;

       A single call to glMultiDrawArraysIndirect is equivalent, assuming no
       errors are generated to:

	       GLsizei n;
	       for (n = 0; n < drawcount; n++)
	       {
		   const DrawArraysIndirectCommand  *cmd;
		   if (stride != 0)
		   {
		       cmd = (const DrawArraysIndirectCommand  *)((uintptr)indirect + n * stride);
		   }
		   else
		   {
		       cmd = (const DrawArraysIndirectCommand  *)indirect + n;
		   }

		   glDrawArraysInstancedBaseInstance(mode,  cmd->first,	 cmd->count,  cmd->primCount, cmd->baseInstance);
	       }

       If a buffer is bound to the GL_DRAW_INDIRECT_BUFFER binding at the time
       of a call to glMultiDrawArraysIndirect, indirect is interpreted as an
       offset, in basic machine units, into that buffer and the parameter data
       is read from the buffer rather than from client memory.

       In contrast to glDrawArraysInstancedBaseInstance(), the first member of
       the parameter structure is unsigned, and out-of-range indices do not
       generate an error.

       Vertex attributes that are modified by glMultiDrawArraysIndirect have
       an unspecified value after glMultiDrawArraysIndirect returns.
       Attributes that aren't modified remain well defined.

NOTES
       The baseInstance member of the DrawArraysIndirectCommand structure is
       defined only if the GL version is 4.2 or greater. For versions of the
       GL less than 4.2, this parameter is present but is reserved and should
       be set to zero. On earlier versions of the GL, behavior is undefined if
       it is non-zero.

       glMultiDrawArraysIndirect is available only if the GL version is 4.3 or
       greater.

ERRORS
       GL_INVALID_ENUM is generated if mode is not an accepted value.

       GL_INVALID_VALUE is generated if stride is not a multiple of four.

       GL_INVALID_VALUE is generated if drawcount is negative.

       GL_INVALID_OPERATION is generated if a non-zero buffer object name is
       bound to an enabled array or to the GL_DRAW_INDIRECT_BUFFER binding and
       the buffer object's data store is currently mapped.

       GL_INVALID_OPERATION is generated if a geometry shader is active and
       mode is incompatible with the input primitive type of the geometry
       shader in the currently installed program object.

       GL_INVALID_OPERATION is generated if mode is GL_PATCHES and no
       tessellation control shader is active.

SEE ALSO
       glDrawArrays(), glDrawArraysInstanced(), glDrawElements(),
       glDrawRangeElements(), glDrawArraysIndirect(),
       glMultiDrawElementsIndirect()

COPYRIGHT
       Copyright © 2012 Khronos Group. This material may be distributed
       subject to the terms and conditions set forth in the Open Publication
       License, v 1.0, 8 June 1999.  http://opencontent.org/openpub/.

AUTHORS
       opengl.org

opengl.org			  03/16/2013	      GLMULTIDRAWARRAYSIND(3G)
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