Edit

Share via

m4x3 - vs

  • Article

Multiplies a 4-component vector by a 4x3 matrix.

Syntax

m4x3 dst, src0, src1

 

where

  • dst is the destination register. Result is a 3-component vector.
  • src0 is a source register representing a 4-component vector.
  • src1 is a source register representing a 4x3 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
m4x3 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) + (src0.w * src1.w);
dest.y = (src0.x * src2.x) + (src0.y * src2.y) + (src0.z * src2.z) + (src0.w * src2.w);
dest.z = (src0.x * src3.x) + (src0.y * src3.y) + (src0.z * src3.z) + (src0.w * src3.w);

The input vector is in register src0. The input 4x3 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 a position vector by a matrix that has no projective effect, such as occurs in model-space transformations. This instruction is implemented as a pair of dot products as shown below.

m4x3   r0.xyz, r1, c0    will be expanded to:

dp4   r0.x, r1, c0
dp4   r0.y, r1, c1
dp4   r0.z, r1, c2

Swizzle and negate modifiers are invalid for the src1 register. The dst and src0 register cannot be the same.

Vertex Shader Instructions