multiplyMatrices( a, b ) {

		const ae = a.elements;
		const be = b.elements;
		const te = this.elements;

		const a11 = ae[ 0 ], a12 = ae[ 3 ], a13 = ae[ 6 ];
		const a21 = ae[ 1 ], a22 = ae[ 4 ], a23 = ae[ 7 ];
		const a31 = ae[ 2 ], a32 = ae[ 5 ], a33 = ae[ 8 ];

		const b11 = be[ 0 ], b12 = be[ 3 ], b13 = be[ 6 ];
		const b21 = be[ 1 ], b22 = be[ 4 ], b23 = be[ 7 ];
		const b31 = be[ 2 ], b32 = be[ 5 ], b33 = be[ 8 ];

		te[ 0 ] = a11 * b11 + a12 * b21 + a13 * b31;
		te[ 3 ] = a11 * b12 + a12 * b22 + a13 * b32;
		te[ 6 ] = a11 * b13 + a12 * b23 + a13 * b33;

		te[ 1 ] = a21 * b11 + a22 * b21 + a23 * b31;
		te[ 4 ] = a21 * b12 + a22 * b22 + a23 * b32;
		te[ 7 ] = a21 * b13 + a22 * b23 + a23 * b33;

		te[ 2 ] = a31 * b11 + a32 * b21 + a33 * b31;
		te[ 5 ] = a31 * b12 + a32 * b22 + a33 * b32;
		te[ 8 ] = a31 * b13 + a32 * b23 + a33 * b33;

		return this;

	}
Multiples the given 3x3 matrices and stores the result
in this matrix.

@param {Matrix3} a - The first matrix.
@param {Matrix3} b - The second matrix.
@return {Matrix3} A reference to this matrix.