This paper presents a new technique for rendering caustics on non-Lambertian surfaces. The method is based on an extension of the photon map which removes previous restrictions limiting the usage to Lambertian surfaces. We add information about the incoming direction to the photons and this allows us to combine the photon map with arbitrary reflectance functions. By using a cone-filter we improve the quality of the radiance estimate in particular at discontinuities. Furthermore we introduce balancing of the photon map which not only reduces the memory requirements but also significantly reduces the rendering time. We have used the method to render caustics on surfaces with reflectance functions varying from Lambertian to glossy specular.
Keywords: Caustics, Photon Map, Filtering, Monte Carlo Ray Tracing, Rendering.
Henrik Wann Jensen: "Rendering Caustics on Non-Lambertian Surfaces". Computer Graphics Forum, vol. 16 (1), pp. 57-64, March 1997