update( plane, lightPosition4D ) {

		// based on https://www.opengl.org/archives/resources/features/StencilTalk/tsld021.htm

		const dot = plane.normal.x * lightPosition4D.x +
			  plane.normal.y * lightPosition4D.y +
			  plane.normal.z * lightPosition4D.z +
			  - plane.constant * lightPosition4D.w;

		const sme = _shadowMatrix.elements;

		sme[ 0 ] = dot - lightPosition4D.x * plane.normal.x;
		sme[ 4 ] = - lightPosition4D.x * plane.normal.y;
		sme[ 8 ] = - lightPosition4D.x * plane.normal.z;
		sme[ 12 ] = - lightPosition4D.x * - plane.constant;

		sme[ 1 ] = - lightPosition4D.y * plane.normal.x;
		sme[ 5 ] = dot - lightPosition4D.y * plane.normal.y;
		sme[ 9 ] = - lightPosition4D.y * plane.normal.z;
		sme[ 13 ] = - lightPosition4D.y * - plane.constant;

		sme[ 2 ] = - lightPosition4D.z * plane.normal.x;
		sme[ 6 ] = - lightPosition4D.z * plane.normal.y;
		sme[ 10 ] = dot - lightPosition4D.z * plane.normal.z;
		sme[ 14 ] = - lightPosition4D.z * - plane.constant;

		sme[ 3 ] = - lightPosition4D.w * plane.normal.x;
		sme[ 7 ] = - lightPosition4D.w * plane.normal.y;
		sme[ 11 ] = - lightPosition4D.w * plane.normal.z;
		sme[ 15 ] = dot - lightPosition4D.w * - plane.constant;

		this.matrix.multiplyMatrices( _shadowMatrix, this.meshMatrix );

	}
Updates the shadow mesh so it follows its shadow-casting reference mesh.

@param {Plane} plane - The plane onto the shadow mesh is projected.
@param {Vector4} lightPosition4D - The light position.