Method multiply

packages/melonjs/src/math/matrix3d.ts:162–252

* multiply both matrix * @param m - Other matrix (Matrix3d or Matrix2d) * @returns Reference to this object for method chaining

(m: Matrix3d | Matrix2d)

	 * @returns Reference to this object for method chaining
	 */
	multiply(m: Matrix3d | Matrix2d) {
		const a = this.val;
		const b = m.val;

		// if the input is a Matrix2d (9 elements), promote to 4x4 layout inline
		// Matrix2d: [a,b,0, c,d,0, tx,ty,1] → 4x4: [a,b,0,0, c,d,0,0, 0,0,1,0, tx,ty,0,1]
		let b00: number, b01: number, b02: number, b03: number;
		let b10: number, b11: number, b12: number, b13: number;
		let b20: number, b21: number, b22: number, b23: number;
		let b30: number, b31: number, b32: number, b33: number;

		if (b.length === 9) {
			b00 = b[0];
			b01 = b[1];
			b02 = 0;
			b03 = 0;
			b10 = b[3];
			b11 = b[4];
			b12 = 0;
			b13 = 0;
			b20 = 0;
			b21 = 0;
			b22 = 1;
			b23 = 0;
			b30 = b[6];
			b31 = b[7];
			b32 = 0;
			b33 = 1;
		} else {
			b00 = b[0];
			b01 = b[1];
			b02 = b[2];
			b03 = b[3];
			b10 = b[4];
			b11 = b[5];
			b12 = b[6];
			b13 = b[7];
			b20 = b[8];
			b21 = b[9];
			b22 = b[10];
			b23 = b[11];
			b30 = b[12];
			b31 = b[13];
			b32 = b[14];
			b33 = b[15];
		}

		const a00 = a[0];
		const a01 = a[1];
		const a02 = a[2];
		const a03 = a[3];
		const a10 = a[4];
		const a11 = a[5];
		const a12 = a[6];
		const a13 = a[7];
		const a20 = a[8];
		const a21 = a[9];
		const a22 = a[10];