Showing papers by "Michael Garland published in 2001"

Hierarchical face clustering on polygonal surfaces

Abstract: Many graphics applications, and interactive systems in particular, rely on hierarchical surface representations to efficiently process very complex models. Considerable attention has been focused on hierarchies of surface approximations and their construction via automatic surface simplification. Such representations have proven effective for adapting the level of detail used in real time display systems. However, other applications such as ray tracing, collision detection, and radiosity benefit from an alternative multiresolution framework: hierarchical partitions of the original surface geometry. We present a new method for representing a hierarchy of regions on a polygonal surface which partition that surface dinto a set of face clusters. These clusters, which are connected sets of faces, represent the aggregate properties of the original surface at different scales rather than providing geometric approximations of varying complexity. We also describe the combination of an effective error metric and a novel algorithm for constructing these hierarchies. CR Categories: I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling—surface and object representations

Efficient adaptive simplification of massive meshes

Abstract: The growing availability of massive polygonal models, and the inability of most existing visualization tools to work with such data, has created a pressing need for memory-efficient methods capable of simplifying very large meshes. In this paper, we present a method for performing adaptive simplification of polygonal meshes that are too large to fit in-core. Our algorithm performs two passes over an input mesh. In the first pass, the model is quantized using a uniform grid, and surface information is accumulated in the form of quadrics and dual quadrics. This sampling is then used to construct a BSP-tree in which the partitioning planes are determined by the dual quadrics. In the final pass, the original vertices are clustered using the BSP-tree, yielding an adaptive approximation of the original mesh. The BSP-tree describes a natural simplification hierarchy, making it possible to generate a progressive transmission and construct level-of-detail representations. In this way, the algorithm provides some of the features associated with more expensive edge contraction methods while maintaining greater computational efficiency. In addition to performing adaptive simplification, our algorithm exhibits output-sensitive memory requirements and allows fine control over the size of the simplified mesh.

Finding and removing features from polyhedra

Abstract: Geometric models of solids often contain small features that we would like to isolate and remove. Examples include bumps, holes, tabs, notches, and decorations. Feature removal can be desirable for numerous reasons, including economical meshing and finite element simulation, analysis of feature purpose, and compact shape representation. In this work, an algorithm is presented that inputs a polyhedral solid, identifies and ranks its candidate features, and outputs solid models of the feature and the original object with the feature removed. Ranking permits a user or higher level software to quickly find the most desirable features for the task at hand. Features are defined in terms of portions of the surface that are classified differently from the rest of the solid’s surface with respect to one or more split planes. This approach to feature definition is more general than many previous methods, and generalizes naturally to quadric surfaces and other implicit surfaces.