Implicit trimmed surfaces are rarely studied since they have no parametric domai n. A method which is related to modeling and rendering of implicit trimmed surfa ces is presented in this paper. First the projection plane is transformed into xy-plane in which the regular grids are partitioned and trimmed areas are d efined by a parametric/implicit curve, then the grids left after trimming are pr ojected onto the implicit surfaces so as to realize polygonization of the implic it trimmed surfaces.