A large amount of computation for various data types is required in 3D graphics rendering processing. A rendering engine has been designed, which consists of triangle setup, edge walk, and a span processor. Especially, new optimum direction processing algorithm (ODPA)is devised to reduce the computing time. ODPA finds the optimum processing direction to minimize processing time for eath triangle, while conventional methods process form left to right. Experimental resuits show that ODPA can reduce the number of clock cycles for edge walk processing by 25% and the amount of computation by 33% when compared to the typical Uni-direction edge functions algorithm.