set( coefficients ) {

		for ( let i = 0; i < 9; i ++ ) {

			this.coefficients[ i ].copy( coefficients[ i ] );

		}

		return this;

	}
Sets the given SH coefficients to this instance by copying
the values.

@param {Array<Vector3>} coefficients - The SH coefficients.
@return {SphericalHarmonics3} A reference to this spherical harmonics.