Geoff Leach

An improved z-buffer CSG rendering algorithm

We present an improved z-buffer based CSG rendering algorithm, based on previous techniques using z-buffer parity based surface clipping. We show that while this type of algorithm has been reported as requiring O( ), (where is the number of primitives), an O( ) (where is depth complexity) algorithm may be substituted. For cases where is less than this translates into a significant performance gain. CR Categories: I.3.5 [Computing Methodologies]: Computer Graphics—Constructive solid geometry (CSG) I.3.3 [Computing Methodologies]: Computer Graphics—Display Algorithms I.3.1 [Computing Methodologies]: Computer Graphics—Hardware Architecture

Elements of a Three-dimensional Graphical User Interface

The graphical user interface (GUI) is now firmly established as the preferred user interface for end users in most situations. Just as decreasing hardware prices and increasing hardware capabilities made two-and-a-half dimensional (2 1/2 D) GUIs affordable in the early eighties and widespread in the ninetees, we believe declining hardware prices and increasing hardware capabilities will make three-dimensional (3D) GUIs possible and affordable in the near future. Three-dimensional GUIs raise many issues of design, metaphor and usability. In this paper we discuss elements of a prototype 3D GUI we are developing.

Improved CSG rendering using overlap graph subtraction sequences

The <i>Sequenced Convex Subtraction</i> (SCS) algorithm for <i>Constructive Solid Geometry</i> (CSG) sequentially subtracts convex volumes from the z-buffer. The performance of the algorithm is determined by the length of the subtraction sequence used. View-independent subtraction sequences are <i>O</i>(<i>n</i>²) in length. These can be reduced to <i>O</i>(<i>kn</i>) if the maximum depth complexity <i>k,</i> which ranges between 1 and <i>n,</i> is known or can be determined.We present an improvement to subtraction sequence generation which uses object space overlap information to give <i>O</i>(<i>n</i>) length sequences in the best case and (unchanged) <i>O</i>(<i>n</i>²) sequences in the worst case. The approach is based on what we term an <i>overlap graph.</i> We also discuss a unifying approach combining overlap graph based processing with the Sequenced Convex Subtraction (SCS) CSG rendering algorithm. Finally, we present experimental results which show performance improvements, depending on the spatial arrangements of objects.

An adaptive octree grid for GPU-based collision detection of deformable objects

In spatial subdivision-based collision detection methods on GPUs, uniform subdivision works well for even triangle spatial distributions, whilst for uneven cases non-uniform subdivision works better. Non-uniform subdivision techniques mainly include hierarchical grids and octrees. Hierarchical grids have been adopted for previous GPU-based approaches, due to their suitability for GPUs. However, octrees offer a better adaptation to distributions. One contribution of this paper is the use of an octree grid that takes a middle path between these two structures, and accelerates collision detection by significantly reducing the number of broad-phase tests which, due to their large quantity, are generally the main bottleneck in performance. Another contribution is to achieve further reduction in the number of tests in the broad phase using a two-stage scheme to improve octree subdivision. The octree grid approach is also able to address the issue of uneven triangle sizes, another common difficulty for spatial subdivision techniques. Compared to the virtual subdivision method which reports the fastest results among existing methods, speedups between 1.0

Virtual subdivision for GPU based collision detection of deformable objects using a uniform grid

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VRML molecular dynamics trajectories

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Hybrid Lighting for faster rendering of scenes with many lights

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