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m3x3 - vs

  • Článek

Multiplies a 3-component vector by a 3x3 matrix.

Syntax

m3x3 dst, src0, src1

 

where

  • dst is the destination register. Result is a 3-component vector.
  • src0 is a source register representing a 3-component vector.
  • src1 is a source register representing a 3x3 matrix, which corresponds to the first of 3 consecutive registers.

Remarks

Vertex shader versions 1_1 2_0 2_x 2_sw 3_0 3_sw
m3x3 x x x x x x

 

The xyz mask is required for the destination register. Negate and swizzle modifiers are allowed for src0 but not for src1.

The following code fragment shows the operations performed.

dest.x = (src0.x * src1.x) + (src0.y * src1.y) + (src0.z * src1.z);
dest.y = (src0.x * src2.x) + (src0.y * src2.y) + (src0.z * src2.z);
dest.z = (src0.x * src3.x) + (src0.y * src3.y) + (src0.z * src3.z);

The input vector is in register src0. The input 3x3 matrix is in register src1, and the next two higher registers, as shown in the expansion below. A 3D result is produced, leaving the other element of the destination register (dest.w) unaffected.

This operation is commonly used for transforming normal vectors during lighting computations. This instruction is implemented as a pair of dot products as shown below.

m3x3 r0.xyz, r1, c0  which will be expanded to:

dp3   r0.x, r1, c0
dp3   r0.y, r1, c1
dp3   r0.z, r1, c2

Vertex Shader Instructions