m4x4

Computes the product of the input vector and a 4x4 matrix.

m4x4 dest, src0, src1

Registers

dest

Destination register.

src0

Input source register.

src1

Input source register.

To learn more about registers, see Registers.

Remarks

The following code fragment shows the operations performed by the m4x4 instruction.

 
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);
dest.w = (src0.x * src4.x) + (src0.y * src4.y) + (src0.z * src4.z);

The input vector is in register src0, the input 3x4 matrix is in register src1 (and the next three higher registers in the same register file--as shown in the expansion below).

This operation is commonly used for transforming a position by a projection matrix. This macro instruction is implemented as a series of dot products as shown below.

m4x4   r5, v0, c3

which is performed as four dot products:
dp4   r5.x, v0, c3
dp4   r5.y, v0, c4
dp4   r5.z, v0, c5
dp4   r5.w, v0, c6

The swizzle and negate modifiers are not allowed on this instruction.

Example

// This example transforms the object with the view and projection matrix.

// shader file
vs.1.0
m4x4 oPos, v0, c0	; transform vertices by view/projection matrix
mov oD0, c4 	; output constant color

// The resultant green object is shown below.

// Additional code is used to initialize the constant registers.

D3DXMATRIX mat, matView, matProj;
D3DXMatrixMultiply(&mat, &matView, &matProj);
D3DXMatrixTranspose(&mat, &mat);
// set C0 with the view and projection matrix
m_pd3dDevice->SetVertexShaderConstant(0, &mat, 4);

// set register c4
float colorGreen[4] = {0, 1, 0, 0};
m_pd3dDevice->SetVertexShaderConstant(4, &colorGreen, 1);

// The first SetVertexShaderConstant method binds the c0 register 
// with the first row of the view/projection matrix (rows 2, 3, and 4 are 
// bound to registers C2, C3, and c4 also). The m4x4 instruction (in the 
// shader file) loads the data.
// The second SetVertexShaderConstant method binds the c4 register 
// with the data for the color green.