Displacement mapping and shell mapping add fine-scale geometric features to meshes and can significantly enhance the realism of an object’s surface representation. Both methods generate geometry within a layer between the base mesh and its offset mesh called a shell. It is not easy to simultaneously achieve high ray tracing performance, low memory consumption, interactive feedback, and ease of implementation, partly because the mapping between shell and texture space is nonlinear. This paper introduces a new efficient approach to perform acceleration structure traversal and intersection tests against microtriangles entirely in texture space by formulating nonlinear rays as degree-2 rational functions. Our method simplifies the implementation of tessellation-free displacement mapping and smooth shell mapping and works even if base mesh triangles are degenerated in uv space.

Abstract Ray tracing is an inherent part of photorealistic image synthesis algorithms. The problem of ray tracing is to find the nearest intersection with a given ray and scene. Although this geometric operation is relatively simple, in practice, we have to evaluate billions of such operations as the scene consists of millions of primitives, and the image synthesis algorithms require a high number of samples to provide a plausible result. Thus, scene primitives are commonly arranged in spatial data structures to accelerate the search. In the last two decades, the bounding volume hierarchy (BVH) has become the de facto standard acceleration data structure for ray tracing‐based rendering algorithms in offline and recently also in real‐time applications. In this report, we review the basic principles of bounding volume hierarchies as well as advanced state of the art methods with a focus on the construction and traversal. Furthermore, we discuss industrial frameworks, specialized hardware architectures, other applications of bounding volume hierarchies, best practices, and related open problems.

Arnold is a physically based renderer for feature-length animation and visual effects. Conceived in an era of complex multi-pass rasterization-based workflows struggling to keep up with growing demands for complexity and realism, Arnold was created to take on the challenge of making the simple and elegant approach of brute-force Monte Carlo path tracing practical for production rendering. Achieving this required building a robust piece of ray-tracing software that can ingest large amounts of geometry with detailed shading and lighting and produce images with high fidelity, while scaling well with the available memory and processing power. Arnold’s guiding principles are to expose as few controls as possible, provide rapid feedback to artists, and adapt to various production workflows. In this article, we describe its architecture with a focus on the design and implementation choices made during its evolutionary development to meet the aforementioned requirements and goals. Arnold’s workhorse is a unidirectional path tracer that avoids the use of hard-to-manage and artifact-prone caching and sits on top of a ray-tracing engine optimized to shoot and shade billions of spatially incoherent rays throughout a scene. A comprehensive API provides the means to configure and extend the system’s functionality, to describe a scene, render it, and save the results.

Global illumination drastically improves visual realism of interactive applications. Although many interactive techniques are available, they have some limitations or employ coarse approximations. For example, general instant radiosity often has numerical error, because the sampling strategy fails in some cases. This problem can be reduced by a bidirectional sampling strategy that is often used in off-line rendering. However, it has been complicated to implement in real-time applications. This paper presents a simple real-time global illumination system based on bidirectional path tracing. The proposed system approximates bidirectional path tracing by using rasterization on a commodity DirectX® 11 capable GPU. Moreover, for glossy surfaces, a simple and efficient artifact suppression technique is also introduced.

In interactive applications such as video games, light maps are often used to generate realistic images. However, baking light maps is time consuming because it is necessary to compute global illumination. This sketch presents a simple and fast rendering system for light maps. Our system exploits ray-bundles on DirectX®11 capable GPUs and outperforms ray tracing based methods. Furthermore, it supports tessellation for DirectX 11 games.

Abstract There are two major ways of calculating ray and parametric surface intersections in rendering. The first is through the use of tessellated triangles, and the second is to use parametric surfaces together with numerical methods such as Newton's method. Both methods are computationally expensive and complicated to implement. In this paper, we focus on Phong Tessellation and introduce a simple direct ray tracing method for Phong Tessellation. Our method enables rendering smooth surfaces in a computationally inexpensive yet robust way.

pixels, 5 seconds); a low polygon head model (800x800 pixels, 8 seconds); a low polygon head model rendered with our method (800x800 pixels, 11 seconds). Note that the silhouettes and shadow boundaries are smooth in our method. There are two major ways of calculating ray and parametric surface intersections in rendering. The first is through the use of micropolygons, and the second is to use parametric surfaces such as NURBS surface together with numerical methods such as Newton Raphson. Both methods are computationally expensive and complicated to implement. In this paper, we introduce a direct ray tracing method for Phong Tessellation. Our method gives analytic solutions that can be readily derived by hand and enables rendering smooth surfaces in a computationally inexpensive yet robust way. 1

Many shading models have been proposed for human hair fibers (see, for example, [Marschner et al. 2003]) and they are used successfully in film productions. Not much attention, however, has been paid to animal furs. The models developed for human hair fibers may not be suitable for animal fur since the scale patterns, medullary types, and pigments are different from those of humans, and greatly different between animals [Deedrick and Koch 2004b]. In this paper we propose an empirical shader to reproduce the detailed appearance of animal fur.

This paper introduces a simple and robust progressive global illumination algorithm based on photon mapping. Progressive photon mapping is a multi-pass algorithm where the first pass is ray tracing followed by any number of photon tracing passes. Each photon tracing pass results in an increasingly accurate global illumination solution that can be visualized in order to provide progressive feedback. Progressive photon mapping uses a new radiance estimate that converges to the correct radiance value as more photons are used. It is not necessary to store the full photon map, and unlike standard photon mapping it possible to compute a global illumination solution with any desired accuracy using a limited amount of memory. Compared with existing Monte Carlo ray tracing methods progressive photon mapping provides an efficient and robust alternative in the presence of complex light transport such as caustics and in particular reflections of caustics.