%mathent; ]> 2010-2014 Khronos Group. glDrawElementsIndirect 3G glDrawElementsIndirect render indexed primitives from array data, taking parameters from memory void glDrawElementsIndirect GLenum mode GLenum type const void *indirect mode Specifies what kind of primitives to render. Symbolic constants GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, and GL_TRIANGLES, are accepted. type Specifies the type of data in the buffer bound to the GL_ELEMENT_ARRAY_BUFFER binding. indirect Specifies the address of a structure containing the draw parameters. glDrawElementsIndirect specifies multiple indexed geometric primitives with very few subroutine calls. glDrawElementsIndirect behaves similarly to glDrawElementsInstanced, execpt that the parameters to glDrawElementsInstanced are stored in memory at the address given by indirect. The parameters addressed by indirect are packed into a structure that takes the form (in C): typedef struct { uint count; uint primCount; uint firstIndex; uint reservedMustBeZero; uint reservedMustBeZero2; } DrawElementsIndirectCommand; glDrawElementsIndirect is equivalent to: void glDrawElementsIndirect(GLenum mode, GLenum type, const void * indirect) { const DrawElementsIndirectCommand *cmd = (const DrawElementsIndirectCommand *)indirect; glDrawElementsInstanced(mode, cmd->count, type, cmd->firstIndex + size-of-type, cmd->primCount); } If a buffer is bound to the GL_DRAW_INDIRECT_BUFFER binding at the time of a call to glDrawElementsIndirect, 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. Note that indices stored in client memory are not supported. If no buffer is bound to the GL_ELEMENT_ARRAY_BUFFER binding, an error will be generated. The results of the operation are undefined if either of the reservedMustBeZero or reservedMustBeZero2 members of the parameter structure are non-zero. However, no error is generated in this case. Vertex attributes that are modified by glDrawElementsIndirect have an unspecified value after glDrawElementsIndirect returns. Attributes that aren't modified remain well defined. GL_INVALID_ENUM is generated if mode is not an accepted value. GL_INVALID_OPERATION is generated if no buffer is bound to the GL_ELEMENT_ARRAY_BUFFER binding, or if such a buffer's data store is currently mapped. 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. glDrawElementsIndirect glDrawArrays, glDrawArraysInstanced, glDrawArraysIndirect, glDrawElements, glDrawRangeElements, Copyright 2010-2014 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/.