A method and apparatus are presented for five-axis NC milling process simulation and dimensional verification. An algorithm is utilized which employs a dexel representation of the workpiece and milling tool to reduce the complexity of the solid representation and associated Boolean operations. This representation is exploited to obtain high computational efficiency which affords real-time visual verification of milling processes. Simulation is presented as animated images while a unique discrete dexel verification algorithm simultaneously performs calculations of milling error between the emerging workpiece and actual design surfaces. Milling errors are depicted by levels of color on the milled workpiece. The verification result precisely reveals the quality of the tool paths in a realistic depiction of the actual process, which is helpful for determining tool path modifications and additional finishing processes. Several graphical results of a software implementation are included to demonstrate the capabilities and robustness of this verification algorithm.