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by gens 1969 days ago
It is used, and most every other compression technique was/is used in video games.

I was thinking of using LZ4, but it doesn't really work that great on floating point, and images are already compressed (png, jpg, and even BCn, can't be compressed much further). So idk. Good thing about lz4 is that it's very simple[0] and probably faster then memcpy().

http://ticki.github.io/blog/how-lz4-works/
1 comments
garaetjjte 1969 days ago
>and even BCn, can't be compressed much further

S3TC is block compression, so if there is repeating data in images it will compress quite well.

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gens 1969 days ago
I tried compressing BC7 (from AMD-s Compressonator) using lz4c and it wasn't much.

Just re-ran it (with -hc, version 1.9.3(latest now)) and: "Compressed 5592544 bytes into 5413783 bytes ==> 96.80%".

7z with "7z a -mx=9 -t7z asd.7z albedo_PNG_BC7_1.KTX" does 5592544 bytes to 4844707 bytes (down to ~87%).

Original file is 10227047 bytes (PNG, RGBA), i can't remember if the ktx has mipmaps.

EDIT: Note that the image is fairly noisy (gravel). Could/should be better with more "artificial" textures.

I don't know if ktx does some extra compression, but, looking at it, i doubt it.

PS I think that BC could be massaged at compression to be better compressible, and i think i read something about that. Don't remember.

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garaetjjte 1969 days ago
Yes, it depends on content and won't do much for grainy surfaces. I don't have AAA game quality textures to compare, but I think for usual textured model it is still worthwhile. eg. this https://milek7.pl/.stuff/somelocotex.png weights 16MiB uncompressed, 5.1MiB as PNG, 5.3MiB as DXT5, and 2.1MiB as DXT5-in-LZ4. (mipmaps included in DXT5)

>PS I think that BC could be massaged at compression to be better compressible, and i think i read something about that. Don't remember.

There's Oodle BC7Prep from RAD Game Tools: http://www.radgametools.com/oodletexture.htm

EDIT: RAD page states that "BC7 blocks that are often very difficult to compress", so that might be also a factor why my DXT5 test compressed much better than your BC7.

EDIT2: Yeah, with BC7 LZ4 only compresses it down to 4.6MiB.

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