Documentation / @interstellar-tools/equations / matMul3

Function: matMul3()

function matMul3(A: Matrix3x3Type, B: Matrix3x3Type): Matrix3x3Type;

Defined in: helpers/mat-mul3.ts:46

Multiply two 3×3 matrices (row-major).

Computes:

$$\mathbf{C}=\mathbf{A}\mathbf{B}$$

Using standard matrix multiplication:

$$C_{r,c}=\sum _{k=0}^2{A}_{r,k}{B}_{k,c}$$

Layout:

• Matrices are treated as row-major: M[row][col].

Common usage:

• Compose rotations / direction cosine matrices (DCMs), e.g. R = R3 * R1 * R3.
• Compose linear transforms in 3D geometry and mapping pipelines.

Parameters

Parameter	Type	Description
A	Matrix3x3Type	Left matrix (3×3, row-major).
B	Matrix3x3Type	Right matrix (3×3, row-major).

Returns

Matrix3x3Type

The product matrix A * B (3×3, row-major).

Example

const A: Matrix3x3Type = [
  [1, 2, 3],
  [0, 1, 4],
  [5, 6, 0]
];

const B: Matrix3x3Type = [
  [-2, 1, 0],
  [3, 0, 0],
  [4, 5, 1]
];

const C = matMul3(A, B);
// C is A*B