An ideal visibility algorithm should a) quickly reject most of the hidden geometry in a model and b) exploit the spatial and perhaps temporal coherence of the images being generated. Ray casting with spatial subdivision does well on criterion (a), but poorly on criterion (b). Traditional Z-buffer scan conversion does well on criterion (b), but poorly on criterion (a). Here we present a hierarchical Z-buffer scan-conversion algorithm that does well on both criteria. The method uses two hierarchical data structures, an object-space octree and an image-space Z pyramid, to accelerate scan conversion. The two hierarchical data structures make it possible to reject hidden geometry very rapidly while rendering visible geometry with the speed of scan conversion. For animation, the algorithm is also able to exploit temporal coherence. The method is well suited to models with high depth complexity, achieving orders of magnitude acceleration in some cases compared to ordinary Z-buffer scan conversion.

The most significant deficiency of most of today’s interactive ray tracers is that they are restricted to static walkthroughs. This restriction is due to the static nature of the acceleration structures used. While the best reported frame rates for static geometric models have been achieved using carefully constructed kd-trees, this article shows that bounding volume hierarchies (BVHs) can be used to efficiently ray trace large static models. More importantly, the BVH can be used to ray trace deformable models (sets of triangles whose positions change over time) with little loss of performance. A variety of efficiency techniques are used to achieve this performance, but three algorithmic changes to the typical BVH algorithm are mainly responsible. First, the BVH is built using a variant of the surface area heuristic conventionally used to build kd-trees. Second, the topology of the BVH is not changed over time so that only the bounding volumes need to be refit from frame-to-frame. Third, and most importantly, packets of rays are traced together through the BVH using a novel integrated packet-frustum traversal scheme. This traversal scheme elegantly combines the advantages of both packet traversal and frustum traversal and allows for rapid hierarchy descent for packets that hit bounding volumes as well as rapid exits for packets that miss. A BVH-based ray tracing system using these techniques is shown to achieve performance for deformable models comparable to that previously available only for static models.

We present a new ray-tracing algorithm for volume rendering which is designed to work efficiently when the data of interest is distributed sparsely through the volume. A simple preprocessing step identifies the voxels representing features of interest. Frequently this set of voxels, arbitrarily distributed in three dimensional space, is a small fraction of the original voxel grid. A mediancut space partitioning scheme, combined with bounding volumes to prune void spaces in the resulting search structure, is used to store the voxels of interest in a kd tree. The tree is then efficiently ray-traced to render the voxel data. The k-d tree is view independent and can be used for animation sequences involving changes in positions of the viewer or positions of lights. We have applied this search structure to render voxel data from MRI, CAT Scan and electron density distributions. 1 Introduction An increasingly important application of computer graphics technology is in providing visualiza...

Abstract--A ray tracing implementation is described that is based on an octree representation of a scene. Rays are traced through the scene by calculating the blocks through which they pass. This calculation is performed in a bottom-up manner through the use of neighbor finding. The octrees are assumed to be implemented by a pointer representation. The most basic operation in computer graphics is the conversion of an internal model of a three-dimensional scene into a two-dimensional scene that lies on the viewplane. The purpose is to generate an image of the

Recent interactive ray tracing performance has been mainly derived from the use of ray packets. Larger ray packets allow for significant amortization of both computations and memory accesses; however, the majority of primitives are still intersected by each ray in a packet. This paper discusses several methods to cull entire ray packets against common primitives (box, triangle, and sphere) that allows an arbitrary number of rays to be tested by a single test. This provides cheap “all miss ” or “all hit ” tests and may substantially improve the performance of an interactive ray tracer. The paper surveys current methods, provides details on three particular approaches using interval arithmetic, bounding planes, and corner rays, describes how the respective bounding primitives can be easily and efficiently constructed, and points out the relation among the different fundamental concepts.

The ray shooting problem arises in many different contexts. For example...

We present an experimental study of some of the important properties of space subdivision structures used to accelerate ray tracing. Location and orientation of partitioning planes, use of bounding volumes, methods to isolate void spaces in hierarchies and choice of traversal methods are examined to determine their effect on performance. This has resulted in the development of a new search structure based on k-d trees, which outperform acceleration schemes that exploit only a subset of the above characteristics. In addition to superior performance and greater adaptivity to scene characteristics, the flexibility of this structure allows it to terminate itself at the correct point, unlike the ad hoc schemes used by existing methods. This structure has been applied successfully to volume visualization applications, resulting in significant performance advantages. 1 Introduction A great deal of research has focused on discovering efficient ways to perform ray tracing, a sophisticated rend...

A hierarchical search structure for ray tracing based on k-d trees is introduced. This data

We present a new method to accelerate the process of finding nearest ray--object intersections in ray tracing. The algorithm consumes an amount of memory more or less linear in the number of objects. The basic ideas can be characterized with a modified BSP--tree and plane traversal. Plane traversal is a fast linear time algorithm to find the closest intersection point in a list of bounding volumes hit by a ray. We use plane traversal at every node of the high outdegree BSP--tree. Our implementation is competitive to fast ray tracing programs. We present a benchmark suite which allows for an extensive comparison of ray tracing algorithms. Keywords: ray tracing, space subdivision, plane traversal, octree, clustering, benchmark scenes 1 Introduction Ray tracing, the well known rendering technique which produces high quality images, simulates geometric optics by tracing rays of light from a virtual viewpoint into an object space. Realistic images are the result of applying illumination m...

In this article, we study some of the important characteristics that affect the performance of ray-tracing hierarchies. Location and orientation of space partitioning planes, the role of bounding volumes, void ares in the nodes of the hierarchy and hierarchy traversal methods are studied individually to determine their effect on performance. We then demonstrate how these characteristics can be combined to obtain object hierarchies that can out-perform some of the best known ray tracing hierarchies. Results are shown using standard ray-tracing benchmarks. CR categories and Subject Descriptors: I.3.3 [Computer Graphics]: Picture/Image Generation; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; General Terms: Algorithms, Graphics. Additional Key Words and Phrases: Ray tracing, computer graphics, bounding volume, extent, partitioning plane, hierarchy, search structure, traversal, characteristics. 1 Introduction In recent years, ray tracing has established itself as an...