Lines Classification in the Conformal Space R^(n+1,1)

International audienceLines classification is the central tool for visibility calculation in dimension $n\ge 2$. It has been previously expressed in Grassmann Algebra, allowing to work with any couple of 2-vectors, which may represent two real lines or not. This article discusses about the nature of lines in the conformal model, searching if such a classification is still valid in R^(n+1,1). First, it shows that the projective classification can be expressed in terms of a {meet} operator. Then, given two real lines, the classification still works in the conformal model, but also allowing us to propound some techniques to identify lines and circles among general 3-vectors

Efficient Real-Time Rendering of Building Information Models

A Building Information Model (BIM) is a powerful concept, since it allows both 2D-drawings and 3D-models of buildings or facilities to be extracted from the same source of data. Compared to a general 3D-CAD model a BIM is a different kind of representation, since it defines not only geometrical data but also information regarding spatial relations and semantics. However, because of the large number of individual objects and high geometric complexity, 3D-data obtained from a BIM are not easily used for real-time rendering without further processing. In this paper we present a culling system specifically designed for efficient real-time rendering of BIM’s. By utilizing the unique properties of a BIM we can form the required data structures without manual modification or expensive preprocessing of the input data. Using hardware occlusion queries together with additional mechanisms based on specific BIM-data, the presented system achieves good culling efficiency for both indoor and outdoor cases

Dynamic worlds in miniature

The World in Miniature (WIM) metaphor allows users to interact and travel efficiently in virtual environments. In addition to the first-person perspective offered by typical VR applications, the WIM offers a second dynamic viewpoint through a hand-held miniature copy of the virtual environment. In the original WIM paper the miniature was a scaled down replica of the whole environment, thus limiting the technique to simple models being manipulated at a single level of scale. Several WIM extensions have been proposed where the replica shows only a part of the virtual environment. In this paper we present an improved visualization of WIM that supports arbitrarily-complex, densely-occluded scenes. In particular, we discuss algorithms for selecting the region of the virtual environment which will be covered by the miniature copy and efficient algorithms for handling 3D occlusion from an exocentric viewpoint.Peer ReviewedPostprint (author’s final draft

Enabling scalability by partitioning virtual environments using frontier sets

We present a class of partitioning scheme that we have called frontier sets. Frontier sets build on the notion of a potentially visible set (PVS). In a PVS, a world is subdivided into cells and for each cell all the other cells that can be seen are computed. In contrast, a frontier set considers pairs of cells, A and B. For each pair, it lists two sets of cells (two frontiers), FAB and FBA. By definition, from no cell in FAB is any cell in FBA visible and vice versa. Our initial use of frontier sets has been to enable scalability in distributed networking. This is possible because, for example, if at time t0 Player1 is in cell A and Player2 is in cell B, as long as they stay in their respective frontiers, they do not need to send update information to each other. In this paper we describe two strategies for building frontier sets. Both strategies are dynamic and compute frontiers only as necessary at runtime. The first is distance-based frontiers. This strategy requires precomputation of an enhanced potentially visible set. The second is greedy frontiers. This strategy is more expensive to compute at runtime, however it leads to larger and thus more efficient frontiers. Network simulations using code based on the Quake II engine show that frontiers have significant promise and may allow a new class of scalable peer-to-peer game infrastructures to emerge

Implementing software occlusion culling for real-time applications

The visualization of complex virtual scenes can be significantly accelerated by applying Occlusion Culling. In this work we introduce a variant of the Hierarchical Occlusion Map method to be used in Real-Time applications. To avoid using real objects geometry we generate specialized conservative Occluders based on Axis Aligned Bounding Boxes which are converted into coplanar quads and then rasterized in CPU using a downscaled Depth Buffer. We implement this method in a 3D scene using a software occlusion map rasterizer module specifically optimized to rasterize Occluder quads into a Depth Buffer. We demonstrate that this approach effectively increases the number of occluded objects without generating significant runtime overhead.Eje: Workshop Computación gráfica, imágenes y visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

Techniques and algorithms for immersive and interactive visualization of large datasets

Advances in computing power have made it possible for scientists to perform atomistic simulations of material systems that range in size, from a few hundred thousand atoms to one billion atoms. An immersive and interactive walkthrough of such datasets is an ideal method for exploring and understanding the complex material processes in these simulations. However rendering such large datasets at interactive frame rates is a major challenge. A scalable visualization platform is developed that is scalable and allows interactive exploration in an immersive, virtual environment. The system uses an octree based data management system that forms the core of the application. This reduces the amount of data sent to the pipeline without a per-atom analysis. Secondary algorithms and techniques such as modified occlusion culling, multiresolution rendering and distributed computing are employed to further speed up the rendering process. The resulting system is highly scalable and is capable of visualizing large molecular systems at interactive frame rates on dual processor SGI Onyx2 with an InfinteReality2 graphics pipeline

Scalable Winner Determination in Advertising Auctions

Internet search results are a growing and highly profitable advertising platform. Search providers auction advertising slots to advertisers on their search result pages. Due to the high volume of searches and the users' low tolerance for search result latency, it is imperative to resolve these auctions fast. Current approaches restrict the expressiveness of bids in order to achieve fast winner determination, which is the problem of allocating slots to advertisers so as to maximize the expected revenue given the advertisers' bids. The goal of our work is to permit more expressive bidding, thus allowing advertisers to achieve complex advertising goals, while still providing fast and scalable techniques for winner determination. We also discuss the application of our framework to advertising in massively multiplayer online games.NS

A stratified rendering algorithm for virtual walkthroughs of large environments

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 73-74).by Rebecca Wen Fei Xiong.M.S