Incremental algorithms for collision detection between polygonalmodels

Fast and accurate collision detection between general polygonal models is a fundamental problem in physically based and geometric modeling, robotics, animation, and computer-simulated environments. Most earlier collision detection algorithms are either restricted to a class of models (such as convex polytopes) or are not fast enough for practical applications. The authors present an incremental algorithm for collision detection between general polygonal models in dynamic environments. The algorithm combines a hierarchical representation with incremental computation to rapidly detect collisions. It makes use of coherence between successive instances to efficiently determine the number of object features interacting. For each pair of objects, it tracks the closest features between them on their respective convex hulls. It detects the objects' penetration using pseudo internal Voronoi cells and constructs the penetration region, thus identifying the regions of contact on the convex hulls. The features associated with these regions are represented in a precomputed hierarchy. The algorithm uses a coherence based approach to quickly traverse the precomputed hierarchy and check for possible collisions between the features. They highlight its performance on different applications     

Debugging multithreaded programs with MPD

MPD, a multiprocessor debugger, is described. In MPD, users specify sequential or parallel event (breakpoint) expressions and associated actions; MPD automatically generates code to recognize these patterns of events and invokes the corresponding actions when the event expressions are satisfied during the program execution. The richness of the expression-specification language gives users a great deal of precision in formulating queries, obviating tedious searches through long traces of multithreaded software. Implementation issues are discussed