We describe an adaptive display algorithm for interactive frame rates during visualization of very complex virtual environments. The algorithm relies upon a hierarchical model representation in which objects are described at multiple levels of detail and can be drawn with various rendering algorithms. The idea behind the algorithm is to adjust image quality adaptively to maintain a uniform, user-specified target frame rate. We perform a constrained optimization to choose a level of detail and rendering algorithm for each potentially visible object in order to generate the "best" image possible within the target frame time. Tests show that the algorithm generates more uniform frame rates than other previously described detail elision algorithms with little noticeable difference in image quality during visualization of complex models. CR Categories and Subject Descriptors: [Computer Graphics]: I.3.3 Picture/Image Generation -- viewing algorithms; I.3.5 Computational Geometry and Object...

The InfiniteReality TM graphics system is the first general-purpose workstation system specifically designed to deliver 60Hz steady frame rate high-quality rendering of complex scenes. This paper describes the InfiniteReality system architecture and presents novel features designed to handle extremely large texture databases, maintain control over frame rendering time, and allow user customization for diverse video output requirements. Rendering performance expressed using traditional workstation metrics exceeds seven million lighted, textured, antialiased triangles per second, and 710 million textured antialiased pixels filled per second.

"Fish tank virtual reality" refers to the use of a standard graphics workstation to achieve real-time display of three-dimensional scenes using stereopsis and dynamic head-coupled perspective. Fish tank VR has a number of advantages over head-mounted immersion VR which make it more practical for many applications. After discussing the characteristics of fish tank VR, we describe a set of three experiments conducted to study the benefits of fish tank VR over a traditional workstation graphics display. These experiments tested user performance under two conditions: (a) whether or not stereoscopic display was used and (b) whether or not the perspective display was coupled dynamically to the positions of a user's eyes. Subjects using a comparison protocol consistently preferred headcoupling without stereo over stereo without head-coupling. Error rates in a tree tracing task similar to one used by Sollenberger and Milgram showed an order of magnitude improvement for headcoupled stereo over ...

3D visual simulation systems must present a world, including terrain, cultural features and 3D icons, in real-time at a level of detail which supports the use for which the system is intended. A “simple ” world lends itself to blasting all the polygons through the workstation’s existing graphics pipeline. However, a “simple ” world is not very realistic and/or does not operate in real-time. For complex worlds, such as that modeled in NPSNET, providing high fidelity in real-time requires the use of hierarchical data structures. We explore the implementation of such a structure on the world modeled by NPSNET utilizing quadtrees.

This paper describes algorithms for predictive database management used in The UC Berkeley Building Walkthrough System. The algorithms forecast a range of possible observer viewpoints during upcoming frames and use precomputed cell visibility information to determine a set of objects likely to be visible to the observer in the near future. For each of these objects, detail elision techniques determine which levels of detail must be stored in a memory resident cache. Cache management algorithms determine which objects to load into memory from disk, and which to replace when the cache is full. Using these algorithms, the system is able to maintain real-time frame rates during interactive visualization of large building models with furniture and radiosity illumination. Key Words: Interactive Visualization, Database Systems, Computer-Aided Architectural Design. 1 Introduction Today, graphics workstations offer a great potential for real-time display of complex 3D environments. An interac...

Database and Display Algorithms for Interactive Visualization of Architectural Models by Thomas Allen Funkhouser Doctor of Philosophy in Computer Science University of California at Berkeley Professor Carlo H. S'equin , Chair This thesis describes a system for interactive walkthroughs of large, fully furnished architectural models. Realistic-looking architectural models with furniture may consist of millions of polygons and require gigabytes of data -- far more than today's workstations can render at interactive frame rates or fit into memory simultaneously. In order to achieve interactive walkthroughs of such large building models, a system must store in memory and render only a small portion of the model in each frame; that is, the portion seen by the observer. As the observer "walks" through the model, some parts of the model become visible and others become invisible; some objects appear larger and others appear smaller. The challenge is to identify the relevant portions of the m...

Realistic-looking architectural models with furniture may consist of millions of polygons and require gigabytes of data -- far more than today's workstations can render at interactive frame rates or store in physical memory. We have developed data structures and algorithms for identifying a small portion of a large model to load into memory and render during each frame of an interactive walkthrough. Our algorithms rely upon an efficient display database that represents a building model as a set of objects, each of which can be described at multiple levels of detail, and contains an index of spatial cells with precomputed cell-to-cell and cell-toobject visibility information. As the observer moves through the model interactively, a real-time visibility algorithm traces sightline beams through transparent cell boundaries to determine a small set of objects potentially visible to the observer. An optimization algorithm dynamically selects a level of detail and rendering algorithm with whi...

this article, we examine some of the work that has been done in these two fields and explore where they are heading. First, we review their often-confusing terminology and provide a brief historical overview. Since both fields rely largely on relatively unusual, and largely immature, hardware technologies, we next provide a high-level introduction to important hardware issues. This is followed by a description of the key approaches to system architecture used by current researchers. We then build on the background provided by these sections to lay out a set of current research issues and directions for future work. Throughout, we attempt to emphasize the many ways in which virtual environments and ubiquitous computing can complement each other, creating an exciting new form of multimedia computing that is far more powerful than either approach would make possible alone.

This paper describes a mechanism for improving rendering rates dynamically during runtime in an interactive threedimensional graphics application. Well-known techniques such as transforming hierarchical geometry into a flat list and removing redundant graphics primitives are often performed off-line on static databases, or continuously every rendering frame. In addition, these optimizations are usually performed over the whole database. We observe that much of the database remains static for a fixed period of time, while other portions are modified continuously (e.g. the camera position), or are repeatedly modified during some finite interval (e.g. during user interaction). We have implemented a runtime optimization mechanism which is sensitive to repeated, local database changes. This mechanism employs timing strategies which optimize only when the cost of optimization will be amortized over a sufficient number of frames. Using this optimization scheme, we observe a rendering speedup of roughly 2.5 in existing applications. We discuss our initial implementation of this mechanism, the improved timing measurements, the issues and assumptions we made, and future improvements. 0

Terrain surfaces are often approximated by geometric meshes to permit efficient rendering. This paper describes how the complexity of an approximating irregular mesh can be varied across its domain in order to minimise the number of displayed facets while ensuring that the rendered surface meets pre-determined resolution requirements. We first present a generalised scheme to represent a mesh over a continuous range of resolutions using the output from conventional single-resolution approximation methods. We then describe an algorithm which extracts a surface from this representation such that the resolution of the surface is enhanced only in specific areas of interest. We prove that the extracted surface is complete, minimal, satisfies the given resolution constraints and meets the Delaunay triangulation criterion if possible. In addition, we present a method of performing smooth visual transitions between selectivelyrefined meshes to permit efficient animation of a terrain scene. 1 In...