yet another PlayStationPortable Documentation

27 Graphic Formats

27.1 1555 ABGR

`15`	`8`	`7`	`0`
`abbb`	`bbgg`	`gggr`	`rrrr`

bit(s)		description
	a	alpha
	b	blue
	g	green
	r	red

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27.2 4444 ABGR

`15`	`8`	`7`	`0`
`aaaa`	`bbbb`	`gggg`	`rrrr`

bit(s)		description
	a	alpha
	b	blue
	g	green
	r	red

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27.3 565 BGR

`15`	`8`	`7`	`0`
`bbbb`	`bggg`	`gggr`	`rrrr`

bit(s)		description
	b	blue
	g	green
	r	red

index

27.4 8888 ABGR

`31`	`24`	`23`	`16`	`15`	`8`	`7`	`0`
`aaaa`	`aaaa`	`bbbb`	`bbbb`	`gggg`	`gggg`	`rrrr`	`rrrr`

bit(s)		description
	a	alpha
	b	blue
	g	green
	r	red

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27.5 swizzling

Internally, the GE processes textures as 16 bytes by 8 rows blocks (independent of actual pixelformat, so a 32*32 32-bit texture is a 128*32 texture from the swizzlings point of view). When you are not swizzling, this means it will have to do scattered reads from the texture as it moves the block into its texture-cache, which has a big impact on performance. To improve on this, you can re-order your textures into these blocks so that it can fetch one entire block by reading sequentially.

00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F
20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F
40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F
60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F
70 71 72 73 74 75 76 77 78 79 7A 7B 7C 7D 7E 7F 0G 0H 0I 0J 0K 0L 0M 0N 0O 0P 0Q 0R 0S 0T 0U 0V
1G 1H 1I 1J 1K 1L 1M 1N 1O 1P 1Q 1R 1S 1T 1U 1V
2G 2H 2I 2J 2K 2L 2M 2N 2O 2P 2Q 2R 2S 2T 2U 2V
3G 3H 3I 3J 3K 3L 3M 3N 3O 3P 3Q 3R 3S 3T 3U 3V
4G 4H 4I 4J 4K 4L 4M 4N 4O 4P 4Q 4R 4S 4T 4U 4V
5G 5H 5I 5J 5K 5L 5M 5N 5O 5P 5Q 5R 5S 5T 5U 5V
6G 6H 6I 6J 6K 6L 6M 6N 6O 6P 6Q 6R 6S 6T 6U 6V
7G 7H 7I 7J 7K 7L 7M 7N 7O 7P 7Q 7R 7S 7T 7U 7V

The block above is a 32 bytes by 8 lines texture block (so it could be a 8*8 32-bit block, or a 16*8 16-bit block). Each pixel is represented here by a vertical index (first value) of 0-7. The second index is the horizontal index, ranging from 0-U. When reorganizing this for swizzling, we will order the data so that when the GE needs to read something in the first 16×8 block, if can just fetch that entire block, instead of offsetting into the texture for each line it has to read. The resulting swizzled portion looks like this:

0G 0H 0I 0J 0K 0L 0M 0N 0O 0P 0Q 0R 0S 0T 0U 0V 1G 1H 1I 1J 1K 1L 1M 1N 1O 1P 1Q 1R 1S 1T 1U 1V
2G 2H 2I 2J 2K 2L 2M 2N 2O 2P 2Q 2R 2S 2T 2U 2V 3G 3H 3I 3J 3K 3L 3M 3N 3O 3P 3Q 3R 3S 3T 3U 3V
4G 4H 4I 4J 4K 4L 4M 4N 4O 4P 4Q 4R 4S 4T 4U 4V 5G 5H 5I 5J 5K 5L 5M 5N 5O 5P 5Q 5R 5S 5T 5U 5V
6G 6H 6I 6J 6K 6L 6M 6N 6O 6P 6Q 6R 6S 6T 6U 6V 7G 7H 7I 7J 7K 7L 7M 7N 7O 7P 7Q 7R 7S 7T 7U 7V

Notice how the rectangular 16*8 blocks have ended up as sequential data, ready for direct reading by the GE.

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27.6 S3TC Compression

Texture formats 8, 9 and 10 are DXT1, DXT3 and DXT5. The hardwares format is a little different from the standard (as you'd find in a .DDS file, for example).

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27.6.1 DXT1

For DXT1, each 4x4 texel block has 2 16-bit 565 colours, and 16 2-bit per-texel fields (8 bytes/block). The PSP hardware expects the per-texel bits to come first, followed by the two colours. Colours are in RGB 565 format.

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27.6.2 DXT3

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27.6.3 DXT5

For DXT3 and DXT5, each 4x4 block has 8 bytes of alpha data followed by 8 bytes of pixel data. The PSP reverses this, so it wants the pixel data followed by alpha data. Also, the pixel data is normally encoded in the same way as the DXT1 blocks, which is also true for the PSP. The encoding is the same as for DXT1 textures, the colours are in RGB 565 format.

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