GPU Textures: Difference between revisions

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This page describes the [[GPU_Commands|GPU commands]] used for textures.
This page is obsolete, see [[GPU/Internal_Registers|here]] for GPU register information, including that of textures.
 
== General information ==
Individual texels in a texture are laid out in memory as a [http://en.wikipedia.org/wiki/Z-order_curve Z-order curve]. Mipmap data is stored directly following the main texture data.
 
== Texture unit setup: Register 0x80 ==
Register 0x80 is used to enable individual texture units.
 
{| class="wikitable" border="1"
!  Bit
!  Description
|-
| 0
| Enable texture unit 0.
|-
| 1
| Enable texture unit 1.
|-
| 2
| Enable texture unit 2.
|}
 
== Configuration of texture unit 0 ==
{| class="wikitable" border="1"
!  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.
 
{| class="wikitable" border="1"
!  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 [[GPU/Procedural_Texture_Generation|procedural texturing]] features.
 
== Texture parameters ==
{| class="wikitable" border="1"
!  Bit
!  Description
!  GL parameter name
|-
| 0
| Normally this is value 0.
|
|-
| 1
| 0 = point sampling (GL_NEAREST), 1 = linear interpolation (GL_LINEAR)
| GL_TEXTURE_MAG_FILTER
|-
| 2
| 0 = point sampling (GL_NEAREST*), 1 = linear interpolation (GL_LINEAR*)
| 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 = GL_CLAMP_TO_BORDER, 2 = GL_REPEAT, 3 = GL_MIRRORED_REPEAT
| GL_TEXTURE_WRAP_S
|-
| 15-12
| Same values as GL_TEXTURE_WRAP_S.
| GL_TEXTURE_WRAP_T
|-
| 24
| 0 = no LOD interpolation (GL_*_MIPMAP_NEAREST), 1 = linear LOD interpolation (GL_*_MIPMAP_LINEAR)
| 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 ==
{| class="wikitable" border="1"
!  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
| HILO8
|
|
|-
| 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
| I4
|
|
|-
| 0xB
| A4
| GL_ALPHA
| GL_UNSIGNED_NIBBLE_EXT
|-
| 0xC
| ETC1
| GL_ETC1_RGB8_OES
|
|-
| 0xD
| ETC1A4
|
|
|}
 
[[Category:GPU]]