An efficient FPGA-based axis-aligned box tool for embedded computer graphics

Abstract

One of the most heavily used kernels of many ray tracing algorithms is the intersection test for a ray with an Axis-Aligned Bounding Box (AABB). Floating point imprecision leads to incorrect ray/AABB intersection test results, which can lead not only to a substantial error in the photorealism of the image during rendering, by producing visually objectionable holes ( false misses ), but also to significant penalties to the ray tracer’s performance and the power consumed, since the traversal is unnecessary ( false hits ). This work suggests a novel architecture that uses carefully-designed directed rounding and intervals for eliminating false misses and for investigating the trade-offs between false hit error rate, area and throughput when downscaling from high precision to low precision. The flexibility of FPGAs in terms of computational structure, pipelin- ing and parallelism in conjunction with the massively parallel floating point operations in ray/AABB tests, makes them a very efficient choice for custom precision hardware computation. A fully-pipelined high-throughput architecture designed in RTL is demonstrated, featuring the provable elimination of false misses while quantifying false hits.