Radiance interpolants for accelerated bounded-error ray tracing

Ray tracers, which sample radiance, are usually regarded as offline renderi ng algorithms that are too slow for interactive use. In this article we pre sent a system that exploits object-space, ray-space, image-space, and tempo ral coherence to accelerate ray tracing. Our system uses per-surface interp olants to approximate radiance while conservatively bounding error. The tec hniques introduced in this article should enhance both interactive and batc h ray tracers. Our approach explicitly decouples the two primary operations of a ray trace r-shading and visibility determination-and accelerates each of them indepen dently. Shading is accelerated by quadrilinearly interpolating lazily acqui red radiance samples. Interpolation error does not exceed a user-specified bound, allowing the user to control performance/quality tradeoffs. Error is bounded by adaptive sampling at discontinuities and radiance nonlinearitie s. Visibility determination at pixels is accelerated by reprojecting interpola nts as the user's viewpoint changes. A fast scan-line algorithm then achiev es high performance without sacrificing image quality. For a smoothly varyi ng viewpoint, the combination of lazy interpolants and reprojection substan tially accelerates the ray tracer. Additionally, an efficient cache managem ent algorithm keeps the memory footprint of the system small with negligibl e overhead.