code: function buildSideFaces() {
  
  			var start = verticesArray.length / 3;
  			var layeroffset = 0;
  			sidewalls( contour, layeroffset );
  			layeroffset += contour.length;
  
  			for ( h = 0, hl = holes.length; h < hl; h ++ ) {
  
  				ahole = holes[ h ];
  				sidewalls( ahole, layeroffset );
  
  				//, true
  				layeroffset += ahole.length;
  
  			}
  
  
  			scope.addGroup( start, verticesArray.length / 3 - start, 1 );
  
  
  		}
docs: Create faces for the z-sides of the shape