The blue-c Distributed Scene Graph

In this paper we present a distributed scene graph architecture for use in the blue-c, a novel collaborative immersive virtual environment. We extend the widely used OpenGL Performer toolkit to provide a distributed scene graph maintaining full synchronization down to vertex and texel level. We propose a synchronization scheme including customizable, relaxed locking mechanisms. We demonstrate the functionality of our toolkit with two prototype applications in our high-performance virtual reality and visual simulation environment

Stride scheduling for time-critical collision detection

We present an event-based scheduling method for time-critical collision detection that meets real-time constraints by balancing and prioritizing computation spent on inter-section tests without starvation. We test each potentially colliding pair of objects at a different frequency, with un-bounded temporal resolution. We show that believability is preserved by adaptively prioritizing intersection tests to re-duce errors in collision detection, using information about the objects and scene. Through the combination of kinetic sweep and prune with stride scheduling we continuously interleave rendering, broad phase collision pruning, nar-row phase intersection testing, and collision response. Our method accrues no per-frame overhead and is interruptible at any point in collision detection, even the broad phase.

Photons from axial-vector radiative decay in a hadron gas

Strange and non-strange axial-vector meson radiative decays contribute to photon production in hadron gas. One- and two-hadron radiative decay modes of $b_{1}(1235)$, $a_{1}(1260)$ and $K_{1}(1270)$ are studied. At 200 MeV temperature and for a narrow range in photon energies they contribute more to the net thermal photon production rate than $\pi\rho\rightarrow \pi\gamma$, $\pi\pi\rightarrow \rho\gamma$ or $\rho\rightarrow\pi\pi\gamma$. They provide significant contribution to the rate for photon energies as high as 1.5--2.0 GeV. For higher energies they are less important.Comment: 10 pages + 7 figures uuencoded in separate file, MSUCL-92

Damping Rate of a Hard Photon in a Relativistic Plasma

The damping rate of a hard photon in a hot relativistic QED and QCD plasma is calculated using the resummation technique by Braaten and Pisarski.Comment: 4 pages, REVTeX, 2 figures (not included), UGI-MT-94-0

Thermal photon production rate from non-equilibrium quantum field theory

In the framework of closed time path thermal field theory we investigate the production rate of hard thermal photons from a QCD plasma away from equilibrium. Dynamical screening provides a finite rate for chemically non-equilibrated distributions of quarks and gluons just as it does in the equilibrium situation. Pinch singularities are shown to be absent in the real photon rate even away from equilibrium.Comment: 10 pages RevTex, 2 ps figures include

Multiresolution Surface and Volume Representations

We present a wavelet-based geometry compression pipeline in the context of hierarchical surface and volume representations. Due to the increasing complexity of geometric models used in a vast number of different application field, new methods have to be devised that enable one to store, transmit and manipulate large amounts of data. Based on a multiresolution wavelet representation, we have developed a complete compression pipeline suitable for geometric data on uniform grids in two and three dimensions. Local and global oracles in wavelet space are employed to control the approximation error in lossy compression settings. Two geometry simplification schemes, which are able to build hierarchical mesh representations, are an essential part of the pipeline. In contrast to the two wavelet-based approximation schemes with each other using several two- and three-dimensional data sets and provide an extensive error and performance analysis. These results emphasize the individual strengths and weaknesses of each of the discussed methods and concepts

Multiresolution Surface and Volume Representations

We present a wavelet-based geometry compression pipeline in the context of hierarchical surface and volume representations. Due to the increasing complexity of geometric models used in a vast number of different application fields, new methods have to be devised that enable one to store, transmit and manipulate large amounts of data. Based on a multiresolution wavelet representation, we have developed a complete compression pipeline suitable for geometric data on uniform grids in two and three dimensions. Local and global oracles in wavelet space are employed to control the approximation error in lossy compression settings. Two geometry simplification schemes, which are able to build hierarchical mesh representations, are an essential part of the pipeline. In contrast to the two wavelet-based approximation schemes, we have devised the progressive tetrahedralization method, an extension of the popular progressive meshes into volumetric settings. We compare the three approximation schemes with each other using several two- and three-dimensional data sets and provide an extensive error and performance analysis. These results emphasize the individual strengths and weaknesses of each of the discussed methods and concepts

Kinetic Sweep and Prune for Multi-Body Continuous Motion

We propose an acceleration scheme for real-time many-body dynamic collision de-tection. We kinetize the sweep and prune method for many-body collision pruning, extending its application to dynamic collision detection via kinetic data structures. In doing so, we modify the method from sample-rate driven to event-driven, with no more events than the original method processed, also removing the per-frame overhead, allowing our method to scale well in terms of frame-rates. Unlike many schemes for many-body collision pruning, ours performs well in both sparse and dense environments, with few or many collisions. Key words: Methodology and Techniques–Graphics data structures and data types; Three-Dimensional Graphics and Realism-Virtual reality; Dynamic collision detection; Kinetic data structure