GS Textures

`06h/07h` TEX0_1/2

0-13 Base pointer in words/64
14-19 Buffer width in pixels/64
20-25 Texture format
- 00h=PSMCT32
- 01h=PSMCT24
- 02h=PSMCT16
- 0Ah=PSMCT16S
- 13h=PSMCT8
- 14h=PSMCT4
- 1Bh=PSMCT8H
- 24h=PSMCT4HL
- 2Ch=PSMCT4HH
- 30h=PSMZ32
- 31h=PSMZ24
- 32h=PSMZ16
- 3Ah=PSMZ16S
26-29 Texture width (width = min(2^value, 1024))
30-33 Texture height (height = min(2^value, 1024))
34 Alpha control (0=texture is RGB, 1=texture is RGBA)
35-36 Color function
- 0=Modulate
- 1=Decal
- 2=Highlight
- 3=Highlight2
37-50 CLUT base pointer in words/64
51-54 CLUT format
- 00h=PSMCT32
- 02h=PSMCT16
- 0Ah=PSMCT16S
55 CLUT uses CSM2 (0=CSM1)
56-60 CLUT entry offset/16 (In CSM2, this value must be 0)
61-63 CLUT cache control
- 0=Do not reload cache
- 1=Reload cache
- 2=Reload cache and copy CLUT base pointer to CBP0
- 3=Reload cache and copy CLUT base pointer to CBP1
- 4=IF CLUT base pointer != CBP0, reload cache and copy pointer to CBP0
- 5=IF CLUT base pointer != CBP1, reload cache and copy pointer to CBP1

`14h/15h` TEX1_1/2

0 LOD (level of detail) calculation method
- 0=LOD=(log2(1/abs(Q))<= 0 (reduced texture)
- 0=nearest
- 1=bilinear
- 2=nearest_mipmap_nearest
- 3=nearest_mipmap_bilinear
- 4=bilinear_mipmap_nearest
- 5=bilinear_mipmap_bilinear
9 Automatic calculation of mipmap levels 1-3 (0=use MIPTBP1)
19-20 L parameter
32-43 K parameter (signed fixed-point, 7 bits whole, 4 bits fractional)

16h/17h TEX2_1/2

20-25 Texture format (same as TEX0)
37-50 CLUT base pointer in words/64
51-54 CLUT format
55 CLUT uses CSM2 (0=CSM1)
56-60 CLUT entry offset/16
61-63 CLUT cache control (same as TEX0) TEX2 is a subset of TEX0. This is useful for modifying texture format and CLUT information when the texture base pointer, width, etc. must stay the same.

`3Fh` TEXFLUSH

Writing any value to this register will invalidate the texture cache. Do this in the following situations:

Using newly transferred texture data
Using newly transferred CLUT data or reloading the CLUT cache
Using framebuffer or zbuffer data as textures

Texture coordinates

The GS supports STQ texture coordinates and UV texel coordinates. The relationship between the two is as follows.

U=(S/Q)*TEX0.texwidth V=(T/Q)*TEX0.texheight

Q is defined by RGBAQ and used for perspective correction. It is not possible to use perspective correction when directly using UV coordinates.

`02h` ST

0-31 S (lower 8 bits are rounded down to zero)
32-63 T (lower 8 bits are rounded down to zero)

S and T are (mostly) IEEE 754-compliant single-precision floating-point values. For both S and T, the range [0.0, 1.0] refers to the whole texture.

`03h` UV

0-13 U
16-29 V

U and V are unsigned 10-bit fixed-point integers with a 4-bit fractional component. The ranges [0, TEXWIDTH] and [0, TEXHEIGHT] for U and V respectively refer to the whole texture.

Color function TEX0 defines four possible color functions that can be used to blend texture and vertex colors:

               RGB                            RGBA
  Modulate     Rv = (Rv * Rt) >> 7            <- Same
               Gv = (Gv * Gt) >> 7            <- Same
               Bv = (Bv * Bt) >> 7            <- Same
               Av = Av                        Av = (Av * At) >> 7
  Decal        Rv = Rt                        <- Same
               Gv = Gt                        <- Same
               Bv = Bt                        <- Same
               Av = Av                        Av = At
  Highlight    Rv = ((Rv * Rt) >> 7) + Av     <- Same
               Gv = ((Gv * Gt) >> 7) + Av     <- Same
               Bv = ((Bv * Bt) >> 7) + Av     <- Same
               Av = Av                        Av = At + Av
  Highlight2   Same as Highlight              Same as Highlight, but Av = At
  

GS Textures

06h/07h TEX0_1/2

14h/15h TEX1_1/2

3Fh TEXFLUSH