This paper identifies opportunities for customizing architectures for graphics applications, such as infrared simulation and geometric visualization. We have studied methods for exploiting custom data formats and datapath widths, and for optimizing graphics operations such as texture mapping and hidden-surface removal. Techniques for balancing the graphics pipeline and for run-time reconfiguration have been implemented. The customized architectures are captured in Handel-C, a C-like language supporting parallelism and flexible data size, and compiled for Xilinx 4000 and Virtex FPGAs. We have also developed an application-programming interface based on the OpenGL standard for automatic speedup of graphics applications, including the Quake 2 action game.