m4x3 - vs

Computes the product of a 4-component vector and a 3x4 matrix.

Syntax

where

• dst is the destination register.
• src0 is a source register.
• src1 is a source register that represents a 3x4 matrix. This means it represents 4 constant registers.

Remarks

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.