Multi-projector systems are increasingly being used to provide large-scale and high-resolution displays for next-generation interactive 3D graphics applications, including large-scale data visualization, immersive virtual environments, and collaborative design. These systems must include a very high-performance and scalable 3D rendering subsystem in order to generate high-resolution images at real-time frame rates. This paper describes a sort-first parallel rendering system for a scalable display wall system built with a network of PCs, graphics accelerators, and portable projectors. The main challenge is to develop scalable algorithms to partition and assign rendering tasks effectively under the performance and functionality constraints of system area networks, PCs, and commodity 3-D graphics accelerators. We have developed three coarse-grained partitioning algorithms, incorporated them into a working prototype system, and run initial experiments aimed at evaluating algorithmic trade-offs and performance bottlenecks in such a system. Results of our experiments indicate that the coarse-grained characteristics of the sort-first architecture are well suited for constructing a parallel rendering system running on a PC cluster.