glDispatchComputeIndirect - OpenGL 4 Reference Pages

Name

glDispatchComputeIndirect — launch one or more compute work groups using parameters stored in a buffer

C Specification

void glDispatchComputeIndirect( GLintptr indirect);

Parameters

indirect: The offset into the buffer object currently bound to the GL_DISPATCH_INDIRECT_BUFFER buffer target at which the dispatch parameters are stored.

Description

glDispatchComputeIndirect launches one or more compute work groups using parameters stored in the buffer object currently bound to the GL_DISPATCH_INDIRECT_BUFFER target. Each work group is processed by the active program object for the compute shader stage. While the individual shader invocations within a work group are executed as a unit, work groups are executed completely independently and in unspecified order. indirect contains the offset into the data store of the buffer object bound to the GL_DISPATCH_INDIRECT_BUFFER target at which the parameters are stored.

The parameters addressed by indirect are packed a structure, which takes the form (in C):

    typedef  struct {
        uint  num_groups_x;
        uint  num_groups_y;
        uint  num_groups_z;
    } DispatchIndirectCommand;

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

    cmd = (const DispatchIndirectCommand  *)indirect;
    glDispatchComputeIndirect(cmd->num_groups_x, cmd->num_groups_y, cmd->num_groups_z);
    }

Unlike glDispatchCompute, no error is generated if any of the num_groups_x, num_groups_y or num_groups_z members of the DispatchIndirectCommand is larger than the value of GL_MAX_COMPUTE_WORK_GROUP_COUNT for the corresponding dimension. In such circumstances, behavior is undefined and may lead to application termination.

Errors

GL_INVALID_OPERATION is generated if there is no active program for the compute shader stage.

GL_INVALID_VALUE is generated if indirect is less than zero or not a multiple of four.

GL_INVALID_OPERATION is generated if no buffer is bound to the GL_DISPATCH_INDIRECT_BUFFER target or if the command would source data beyond the end of the buffer object's data store.

Associated Gets

glGet with argument GL_MAX_COMPUTE_WORK_GROUP_COUNT