Method and apparatus for efficient depth prepass

An apparatus comprising:

• a graphics pipeline;
• a specified portion of a graphics pipeline to perform a first pass on graphics data with only depth rendering active to perform Zmax-mask occlusion culling using data indicating rasterizer sample coverage;
• a coarse depth buffer to be initialized by the specified portion of the graphics pipeline during the first pass, the coarse depth buffer storing depth data at a level of granularity less than that stored in a per-pixel depth buffer, wherein the per-pixel depth buffer includes no per-pixel depth data during the first pass, and wherein updates to the coarse depth buffer are determined based on coverage and depth information received from a rasterizer, and wherein following the first pass a hierarchical representation of the depth data is added to a memory/cache hierarchy;
• and
• the graphics pipeline to perform a second pass on the graphics data following the first pass utilizing values in the coarse depth buffer initialized by the first pass.

A non-transitory machine-readable medium having program code stored thereon which, when executed by a machine, causes the machine to perform the operations of:

• performing a first pass through a specified portion of a graphics pipeline with only depth rendering active to perform Zmax-mask occlusion culling using data indicating rasterizer sample coverage;
• initializing a coarse depth buffer within the specified portion of the graphics pipeline during the first pass, the coarse depth buffer storing depth data at a level of granularity less than that stored in a per-pixel depth buffer, wherein the per-pixel depth buffer includes no per-pixel depth data during the first pass, and wherein updates to the coarse depth buffer are determined based on coverage and depth information received from a rasterizer, and wherein following the first pass a hierarchical representation of the depth data is added to a memory/cache hierarchy;
• and
• performing a second pass through the graphics pipeline following the first pass, the second pass utilizing the full graphics pipeline and further utilizing values in the coarse depth buffer initialized by the first pass.