_removeAllVerticesFromFace( face ) {

		if ( face.outside !== null ) {

			// reference to the first and last vertex of this face

			const start = face.outside;
			let end = face.outside;

			while ( end.next !== null && end.next.face === face ) {

				end = end.next;

			}

			this.assigned.removeSubList( start, end );

			// fix references

			start.prev = end.next = null;
			face.outside = null;

			return start;

		}

	}
Removes all the visible vertices that a given face is able to see which are stored in
the 'assigned' vertex list.

@private
@param {Face} face - The target face.
@return {VertexNode|undefined} A reference to this convex hull.