2010-2013
Khronos Group.
glDrawArraysIndirect
3G

# glDrawArraysIndirect

render primitives from array data, taking parameters from memory

## C Specification

                    void glDrawArraysIndirect
                    GLenum mode
                    const void *indirect

## 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 a structure containing the draw parameters.

## Description

`glDrawArraysIndirect` specifies multiple geometric primitives with very few subroutine calls. `glDrawArraysIndirect` behaves similarly to glDrawArraysInstancedBaseInstance, execept that the parameters to glDrawArraysInstancedBaseInstance 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  first;
            uint  baseInstance;
        } DrawArraysIndirectCommand;

        const DrawArraysIndirectCommand *cmd = (const DrawArraysIndirectCommand *)indirect;
        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 `glDrawArraysIndirect`, `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 `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 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,

## Copyright

Copyright 2010-2013 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/.