texm3x2tex - ps
Performs the final row of a 3x2 matrix multiply and uses the result to do a texture lookup. texm3x2tex must be used in conjunction with the texm3x2pad - ps instruction.
Syntax
texm3x2tex dst, src |
---|
where
- dst is the destination register.
- src is a source register.
Remarks
Pixel shader versions | 1_1 | 1_2 | 1_3 | 1_4 | 2_0 | 2_x | 2_sw | 3_0 | 3_sw |
---|---|---|---|---|---|---|---|---|---|
texm3x2tex | x | x | x |
The instruction is used as one of two instructions representing a 3x2 matrix multiply operation. This instruction must be used with the texm3x2pad - ps instruction.
When using these two instructions, texture registers must use the following sequence.
tex t(n) // Define tn as a standard 3-vector (tn must
// be defined in some way before it is used)
texm3x2pad t(m), t(n) // where m > n
// Perform first row of matrix multiply
texm3x2tex t(m+1), t(n) // Perform second row of matrix multiply
// to get (u,v) to sample texture
// associated with stage m+1
Here is more detail about how the 3x2 multiply is accomplished.
The texm3x2pad instruction performs the first row of the multiply to find u'.
u' = t(n)RGB * TextureCoordinates(stage m)UVW
The texm3x2tex instruction performs the second row of the multiply to find v'.
v' = t(n)RGB * TextureCoordinates(stage m+1)UVW
The texm3x2tex instruction samples the texture on stage (m+1) with (u',v') and stores the result in t(m+1).
t(m+1)RGB = TextureSample(stage m+1)RGB using (u', v' ) as coordinates
Examples
Here is an example shader with the texture maps and the texture stages identified.
ps_1_1
tex t0 // Bind texture in stage 0 to register t0
texm3x2pad t1, t0 // First row of matrix multiply
texm3x2tex t2, t0 // Second row of matrix multiply to get (u,v)
// with which to sample texture in stage 2
mov r0, t2 // Output result
This example requires the following textures in the following texture stages.
- Stage 0 takes a map with (x,y,z) perturbation data.
- Stage 1 holds texture coordinates. No texture is required in the texture stage.
- Stage 2 holds both texture coordinates as well as a 2D texture set at that texture stage.
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