code: public OGCGeometry getGeometry(DeferredObject[] args) {
  		if (isConstant) {
  			if (constantGeometry == null) {
  				constantGeometry = getGeometry(args[argIndex]);
  			} 
  			
  			return constantGeometry;
  		} else {
  			// not constant, so we have to rebuild the geometry
  			// on every call
  			return getGeometry(args[argIndex]);
  		}
  	}
docs: Reads the corresponding geometry from the deferred object list
  or returns the cached geometry if argument is constant.
  
  @param args
  @return