For almost two decades researchers have argued that ray tracing will eventually become faster than the rasterization technique that completely dominates todays graphics hardware. However, this has not happened yet. Ray tracing is still exclusively being used for off-line rendering of photorealistic images and it is commonly believed that ray tracing is simply too costly to ever challenge rasterization-based algorithms for interactive use. However, there is hardly any scientific analysis that supports either point of view. In particular there is no evidence of where the crossover point might be, at which ray tracing would eventually become faster, or if such a point does exist at all.

Rasterization hardware provides interactive frame rates for rendering dynamic scenes, but lacks the ability of ray tracing required for efficient global illumination simulation. Existing ray tracing based methods yield high quality renderings but are far too slow for interactive use. We present a new parallel global illumination algorithm that perfectly scales, has minimal preprocessing and communication overhead, applies highly efficient sampling techniques based on randomized quasi-Monte Carlo integration, and benefits from a fast parallel ray tracing implementation by shooting coherent groups of rays. Thus a performance is achieved that allows for applying arbitrary changes to the scene, while simulating global illumination including shadows from area light sources, indirect illumination, specular effects, and caustics at interactive frame rates. Ceasing interaction rapidly provides high quality renderings.

In a distribution ray tracer, the crucial part of the direct lighting calculation is the sampling strategy for shadow ray testing. Monte Carlo integration with importance sampling is used to carry out this calculation. Importance sampling involves the design of integrand-specific probability density functions which are used to generate sample points for the numerical quadrature. Probability density functions are presented that aid in the direct lighting calculation from luminaires of various simple shapes. A method for defining a probability density function over a set of luminaires is presented that allows the direct lighting calculation to be carried out with one sample, regardless of the number of luminaires. CR Categories and Subject Descriptors: G.1.4 [Mathematical Computing]: Quadrature and Numerical Differentiation; I.3.0 [Computer Graphics]: General; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism. Additional Key Words and Phrases: direct lighting, importanc...

This paper presents a new interactive rendering and display technique for complex scenes with expensive shading, such as global illumination. Our approach combines sparsely sampled shading (points) and analytically computed discontinuities (edges) to interactively generate high-quality images. The edge-and-point image is a new compact representation that combines edges and points such that fast, table-driven interpolation of pixel shading from nearby point samples is possible, while respecting discontinuities. The edge-and-point renderer is extensible, permitting the use of arbitrary shaders to collect shading samples. Shading discontinuities, such as silhouettes and shadow edges, are found at interactive rates. Our software implementation supports interactive navigation and object manipulation in scenes that include expensive lighting effects (such as global illumination) and geometrically complex objects. For interactive rendering we show that high-quality images of these scenes can be rendered at 8–14 frames per second on a desktop PC: a speedup of 20–60 over a ray tracer computing a single sample per pixel.

this paper, we present a system that exploits object-space, rayspace, image-space and temporal coherence to accelerate ray tracing. Our system uses per-surface interpolants to approximate radiance, while conservatively bounding error. The techniques we introduce in this paper should enhance both interactive and batch ray tracers.

: This paper presents a new importance sampling strategy for Monte Carlo ray tracing in which a rough estimate of the irradiance based on the photon map is combined with the local reflection model to construct more efficient probability density functions that can be used in an importance sampling scheme. The algorithm gives unbiased results, handles arbitrary reflection models and it is particularly efficient in scenes with highly non-uniform indirect illumination. Initial results and comparisons with traditional importance sampling strategies indicate a reduction in the noise level of more than 70% Key Words: Global Illumination, Path Tracing, Importance Sampling, Photon Map 1 Introduction Photorealistic rendering requires accurate simulation of global illumination and much work has been done in this area in the last 10 years. The problem was actually solved in 1986 by Kajiya [6] using a method called path tracing. This method is basically a brute force Monte Carlo simulat...

In this paper we present a 5D tree structure to cache illumination information gained during Monte Carlo ray tracing. The structure is elegant and simple to use. It is adaptive and makes abstraction of the complexity of the input scene automatically. We then show how the information in this structure can be used to reduce the variance of the Monte Carlo process. Unlike earlier approaches the techniques presented here do not introduce a bias in the results.

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Algorithms for image synthesis render photo-realistic imagery, given the description of a scene. Physically based rendering specifically stresses the physical correctness of the algorithms and their results. The algorithms perform an accurate simulation of the behaviour of light, in order to faithfully render global illumination effects such as soft shadows, glossy reflections and indirect illumination. In this dissertation we investigate image-based Monte Carlo rendering algorithms. We pay special attention to their correctness, their versatility and their efficiency. First of all, we discuss theoretical frameworks that describe the global illumination problem. These formal mathematical models are the first step to ensure the correctness of the eventual results. Moreover, they allow to apply standard numerical techniques to compute a solution. We give an overview of existing models, which are based on the rendering equation and the potential equation. We then introduce a model based ...

Distribution ray tracing uses Monte Carlo integration to solve the rendering equation. This technique was introduced by Cook et. al, and was notable because of its simplicity and its ability to simulate areal luminaires, camera lens e ects, motion blur, and imperfect specular re ection[5]. Distribution