_addVertexToFace( vertex, face ) {

		vertex.face = face;

		if ( face.outside === null ) {

			this.assigned.append( vertex );

		} else {

			this.assigned.insertBefore( face.outside, vertex );

		}

		face.outside = vertex;

		return this;

	}
Adds a vertex to the 'assigned' list of vertices and assigns it to the given face.

@private
@param {VertexNode} vertex - The vertex to add.
@param {Face} face - The target face.
@return {ConvexHull} A reference to this convex hull.