Molds and dies with sculptured surfaces are usually fabricated using numerically controlled (NC) 3-axis milling machines with a spherical cutter. Fine and precise visualization of the workpiece shape resulted by an NC miffing operation is necessary for manufacturing a product with good surface quality. Result shape of the workpiece can be computed by geometrically simulating the miffing process using solid models of the tool swept volume and the stock object. Miffing simulation method based on a discrete representation of the workpiece model is widely used. This method approximates the workpiece shape as a collection of thin cubic solids called dexels. Direct displaying of dexels is not suitable for the visualization because of the staircase error remaining on the model surface. In this paper, the authors propose two technologies for improving the visualization quality of the workpiece model in the dexel representation. The first method realizes correct and smooth rendering of the model using the surface normal information at the top point of each dexel. In order to realize the precise rendering without consuming the extra memory, the second method localizes the visible portion of the workpiece and transforms ouly such portion to very fine dexels. An experimental program is implemented and high quality visualization of some complex milling results is demonstrated.
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