GLAPI/glDrawArraysIndirect

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glDrawArraysIndirect
Core in version 4.4
Core since version 4.0
Core ARB extension ARB_draw_indirect

glDrawArraysIndirect: render primitives from array data, taking parameters from memory

Function Definition

 void glDrawArraysIndirect(GLenum mode​, const void *indirect​);
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 a byte offset (cast to a pointer type) into the buffer bound to GL_DRAW_INDIRECT_BUFFER​, which designates the starting point of the structure containing the draw parameters.

Description

glDrawArraysIndirect specifies multiple geometric primitives with very few subroutine calls. glDrawArraysIndirect behaves similarly to glDrawArraysInstancedBaseInstance, except that the parameters to glDrawArraysInstancedBaseInstance are stored in the buffer bound to GL_DRAW_INDIRECT_BUFFER​, offset by indirect​ bytes.

The parameters referenced by indirect​ are packed into a structure that takes the form (in C):

    typedef  struct {
        uint  count;
        uint  instanceCount;
        uint  first;
        uint  baseInstance;
    } DrawArraysIndirectCommand;
 
    const DrawArraysIndirectCommand  *cmd  = (const DrawArraysIndirectCommand  *)indirect;
    glDrawArraysInstancedBaseInstance(mode,  cmd->first,  cmd->count,  cmd->instanceCount, cmd->baseInstance);

indirect​ is interpreted as an offset, in basic machine units, into the buffer bound to GL_DRAW_INDIRECT_BUFFER​ at the time of the call. The parameter data stored there is read from the buffer and executed.

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 glDrawArraysIndirect have an unspecified value after glDrawArraysIndirect 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.

Errors

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

GL_INVALID_OPERATION​ is generated if buffer object name zero is bound to the GL_DRAW_INDIRECT_BUFFER​ binding.

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

glBindVertexArray, glDrawArrays, glDrawArraysInstanced, glDrawArraysInstancedBaseInstance, glDrawElementsIndirect, glMultiDrawArrays, glMultiDrawArraysIndirect

Copyright

Copyright © 2010 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/.