Random accessible lossless parameter data compression for tile based 3D computer graphics systems
A method and apparatus are provided for compressing vertex parameter data in a 3D computer graphic system, where the vertex parameter data is a data block relating to a plurality of vertices used for rendering an image. The data relating to each vertex includes multiple byte data relating to at least one parameter. The parameters include X, Y and Z coordinates and further coordinates for texturing and shading. The multiple byte data is divided into individual bytes and bytes with corresponding byte positions relating to each vertex are grouped together to form a plurality of byte blocks.
1. A method of compressing data in a processing system, the data comprising a plurality of values, the values having a same multiple-byte format, the method comprising:
grouping together bytes with corresponding byte significance to form a plurality of byte blocks; and
compressing a byte block of the plurality of byte blocks using a compression algorithm comprising:
on determining that all the bytes of the byte block have the same byte value, replacing all the bytes of the said byte block with a single byte having the said same byte value to form a compressed byte block.
2. The method of claim 1 , wherein the method further comprises:
providing a flag to indicate that the compressed byte block has been compressed by replacing all of the bytes of the byte block with the said same byte value.
3. The method of claim 1 wherein the processing system comprises a computer graphics system.
4. The method of claim 3 , wherein the computer graphics system comprises a tile-based 3D computer graphics system.
5. The method of claim 1 , wherein the plurality of values are parameter values.
6. The method of claim 1 , wherein the data is vertex parameter data, and wherein the plurality of values relate to a respective plurality of vertices.
7. The method of claim 6 , wherein the vertex parameter data is randomly accessible from the compressed byte block.
8. An apparatus configured to compress data in a processing system, wherein the data comprises a plurality of values, the values having a same multiple-byte format;
wherein the apparatus is configured to:
group together bytes with corresponding byte significance to form a plurality of byte blocks;
wherein the apparatus comprises at least one compression unit configured to compress a byte block of the plurality of byte blocks using a compression algorithm, the compression comprising:
on determining that all the bytes of the byte block have the same byte value, replacing all the bytes of the said byte block with a single byte having the said same byte value to form a compressed byte block.
9. The apparatus of claim 8 , wherein the apparatus is further configured to
provide a flag to indicate that the compressed byte block has been compressed by replacing all of the bytes of the byte block with the said same byte value.
10. The apparatus of claim 9 wherein the processing system comprises a computer graphics system.
11. The apparatus of claim 10 wherein the computer graphics system comprises a tile-based 3D computer graphics system.
12. The apparatus of claim 8 , further comprising a memory configured to store the compressed byte block.
13. A method of reconstructing values from compressed data in a processing system, the values having a same multiple-byte format, wherein the compressed data comprises a compressed byte block comprising a byte value, the method comprising:
decompressing the compressed byte block to provide a decompressed byte block, the decompressing comprising using the byte value of the compressed byte block for each byte value of the decompressed byte block, and
reconstructing values having the same multiple-byte format by using the decompressed byte block to represent, in the values, bytes with corresponding byte significance.
14. The method of claim 13 wherein the processing system comprises a computer graphics system.
15. The method of claim 14 , wherein the computer graphics system comprises a tile-based 3D computer graphics system.
16. The method of claim 13 , wherein the values are parameter values.
17. An apparatus for reconstructing values from compressed data in a processing system, the values having a same multiple-byte format, wherein the compressed data comprises a compressed byte block comprising a byte value, the apparatus comprising:
at least one decompression unit configured to
decompress the compressed byte block to provide a decompressed byte block, comprising using the byte value of the compressed byte block for each byte value of the decompressed byte block, and
reconstruct values having the same multiple-byte format by using the decompressed byte block to represent, in the values, bytes with corresponding byte significance.
18. The apparatus of claim 17 , wherein the processing system comprises a computer graphics system.
19. The apparatus of claim 18 , wherein the computer graphics system comprises a tile-based 3D computer graphics system.
20. The apparatus of claim 17 , further comprising a memory configured to store the decompressed byte block.