Approximate Ray‐Tracing on the GPU with Distance Impostors

Abstract

This paper presents a fast approximation method to obtain the point hit by a reflection or refraction ray. The calculation is based on the distance values stored in environment map texels. This approximation is used to localize environment mapped reflections and refractions, that is, to make them depend on where they occur. On the other hand, placing the eye into the light source, the method is also good to generate real-time caustics. Computing a map for each refractor surface, we can even evaluate multiple refractions without tracing rays. The method is fast and accurate if the scene consists of larger planar faces, when the results are similar to that of ray-tracing. On the other hand, the method suits very well to the GPU architecture, and can render ray-tracing and global illumination effects with few hundred frames per second. The primary application area of the proposed method is the introduction of these effects in games.

A Flexible Pinhole Camera Model for Coherent Nonuniform Sampling

“…Environment mapped reflections are incorrect for objects close to the reflector. Approximating these objects with billboards or depth images [18] improves reflection accuracy. Using CoNUS depth images as relief textures or to approximate reflected objects brings sampling flexibility without a considerable increase of the cost of ray / depth image intersection.…”

“…[17]), image-based rendering (e.g. [18]), and approximations of the reflected scene. We only discuss the fourth category since it is the category where the CoNUS specular reflection rendering method falls.…”

Indirect diffuse and glossy illumination on the GPU

“…Comparing to Lightcuts [Walter et al 2005], our clustering is simpler, but is executed in real-time by the graphics hardware, and replaces the cluster by an area light. The radiance values of the single cube map are then localized for the shaded points taking into account the distances of the environment, the shaded points, and of the reference point, similarly to the approximate ray-tracing method [Szirmay-Kalos et al 2005]. However, the new technique uses a different localization approach developed particularly for diffuse and glossy reflections.…”

“…a sphere or a cube) of the environment is intersected by the reflection ray to obtain the visible point. The Approximate RayTracing approach [Szirmay-Kalos et al 2005], on the other hand, stores the distance values between the reference point and the environment and applies an iterative process to identify the real hit point of those rays that are not originated in the reference point.…”

Depicting procedural caustics in single images

“…The third step projects the caustic map onto the scene. Several different variations have been proposed, including minimizing the number of photons [Szirmay-Kalos et al 2005], efficient schemes to collect photons in a caustic map [Wyman and Davis 2006], or computing caustics for each object, rather than for each light source [Wei and Kaihuai 2007]. Various techniques which improve quality and performance are also known [Kruger et al 2006;Wyman and Dachsbacher 2008;Wyman 2008].…”