Stencil buffer data compression

摘要

A raster operations (ROP) unit is configured to compress stencil values included in a stencil buffer. The ROP unit divides the stencil values into groups, subdivides each group into two halves, and selects an anchor value for each half. If the difference between each of the stencil values and the corresponding anchor lies within an offset range, and the difference between the two anchors lies within a delta range, then the group is compressible. For a compressible group, the ROP unit encodes the anchor value, offsets from anchors, and an anchor delta. This encoding enables the ROP unit to operate on the compressed group instead of the uncompressed stencil values, reducing the number of memory and computational operations associated with the stencil values. Consequently, the ROP unit reduces memory bandwidth use, reduces power consumption, and increases rendering rate compared to conventional ROP units that implement less flexible compression techniques.

主权项

1. A computer-implemented method for compressing stencil values, the method comprising:
selecting a first anchor for a first batch of stencil values that includes a first stencil value; selecting a second anchor for a second batch of stencil values that includes a second stencil value; computing a first offset that is included in a first plurality of offsets based on the first stencil value and the first anchor, wherein the first plurality is associated with the first batch; computing a second offset that is included in a second plurality of offsets based on the second stencil value and the second anchor, wherein the second plurality is associated with the second batch; computing an anchor delta based on the first anchor and the second anchor; and storing the first anchor, the anchor delta, the first plurality of offsets, and the second plurality of offsets in a memory as a first compressed stencil data instead of storing the first batch and the second batch in the memory as uncompressed stencil data.