This page describes the GPU commands used for textures.
General information
Individual texels in a texture are laid out in memory as a Z-order curve.
Texture unit setup: Register 0x80
Register 0x80 is used to enable individual texture units.
| Bit
|
Description
|
| 0
|
Enable texture unit 0.
|
| 1
|
Enable texture unit 1.
|
| 2
|
Enable texture unit 2.
|
Configuration of texture unit 0
| Register ID
|
Description
|
| 0x0081
|
Border color (unverified)
|
| 0x0082
|
Bits 16-31 are the texture width. Bits 0-15 are the texture height. The maximum texture size in either direction is 1024.
|
| 0x0083
|
Texture parameters (filtering, wrapping), see below.
|
| 0x0084
|
LOD setup?
|
| 0x0085
|
Physical address of texture data (divided by 8).
|
| 0x0086
|
Physical address of texture data for cube mapping?
|
| 0x0087
|
Physical address of texture data for cube mapping?
|
| 0x0088
|
Physical address of texture data for cube mapping?
|
| 0x0089
|
Physical address of texture data for cube mapping?
|
| 0x008A
|
Physical address of texture data for cube mapping?
|
| 0x008B
|
Shadow related?
|
| 0x008E
|
Texture format (see below)
|
Configuration of texture units 1 and 2
Texture units 1 and 2 use a configuration block similar to the one of texture unit 0. They are based at registers 0x0091 and 0x0099.
| Index word
|
Description
|
| 0-4
|
Same as for texture unit 0
|
| 5
|
Texture format (see below)
|
Configuration of texture unit 3
The configuration block for texture unit 3 seems to be vastly different from the other texture units. Instead, registers 0x00A8 through 0x00B7 are used to configure procedural texturing features.
Texture parameters
| Bit
|
Description
|
GL parameter name
|
| 0
|
Normally this is value 0.
|
|
| 1
|
0 = GL_NEAREST, 1 = GL_LINEAR.
|
GL_TEXTURE_MAG_FILTER
|
| 2
|
1 = GL_LINEAR, GL_LINEAR_MIPMAP_NEAREST, or GL_LINEAR_MIPMAP_LINEAR. Value zero otherwise.
|
GL_TEXTURE_MIN_FILTER
|
| 3
|
Unused?
|
?
|
| 5-4
|
2 = texture color type 0xC, 0 otherwise.(Enable/disable texture data compression?) 0 = unknown, 1 = unknown, 3 = same effect as value 2.
|
|
| 7-6
|
Unused
|
| 11-8
|
0 = GL_CLAMP_TO_EDGE, 1=unknown, 2=GL_REPEAT, 3=unknown.
|
GL_TEXTURE_WRAP_S
|
| 15-12
|
Same values as GL_TEXTURE_WRAP_S.
|
GL_TEXTURE_WRAP_T
|
| 24
|
1 = GL_NEAREST_MIPMAP_LINEAR, or GL_LINEAR_MIPMAP_LINEAR. Value zero otherwise.
|
GL_TEXTURE_MIN_FILTER
|
| 27-25
|
Unused?
|
| 30-28
|
When some flag=1: value1=GL_TEXTURE_2D, value0 when the input parameter is not GL_TEXTURE_2D. When some flag=0: 0=GL_TEXTURE_2D, 1-4=unknown.
|
?
|
| 31
|
Unused?
|
?
|
Texture color types
| Value
|
Description
|
GL Format
|
GL Data Type
|
| 0x0
|
RGBA8888
|
GL_RGBA
|
GL_UNSIGNED_BYTE
|
| 0x1
|
RGB888
|
GL_RGB
|
GL_UNSIGNED_BYTE
|
| 0x2
|
RGBA5551
|
GL_RGBA
|
GL_UNSIGNED_SHORT_5_5_5_1
|
| 0x3
|
RGB565
|
GL_RGB
|
GL_UNSIGNED_SHORT_5_6_5
|
| 0x4
|
RGBA4444
|
GL_RGBA
|
GL_UNSIGNED_SHORT_4_4_4_4
|
| 0x5
|
IA8
|
GL_LUMINANCE_ALPHA
|
GL_UNSIGNED_BYTE
|
| 0x6
|
|
|
|
| 0x7
|
I8
|
GL_LUMINANCE
|
GL_UNSIGNED_BYTE
|
| 0x8
|
A8
|
GL_ALPHA
|
GL_UNSIGNED_BYTE
|
| 0x9
|
IA44
|
GL_LUMINANCE_ALPHA
|
GL_UNSIGNED_BYTE_4_4_EXT
|
| 0xA
|
|
|
|
| 0xB
|
A4
|
GL_ALPHA
|
GL_UNSIGNED_NIBBLE_EXT
|
| 0xC
|
ETC1
|
GL_ETC1_RGB8_OES
|
|
| 0xD
|
ETC1A4
|
|
|