code: function ( inVertexX, inVertexY ) {			// private
  		var vertex = {
  				id: this.vertices.length,	// vertex id, representing input sequence
  				x: inVertexX,				// coordinates
  				y: inVertexY,
  			};
  		this.vertices.push( vertex );
  		return	vertex;
  	}
docs: /*	Operations