Highly detailed geometric models are rapidly becoming commonplace in computer graphics. These models, often represented as complex triangle meshes, challenge rendering performance, transmission bandwidth, and storage capacities. This paper introduces the progressive mesh (PM) representation, a new scheme for storing and transmitting arbitrary triangle meshes. This efficient, lossless, continuous-resolution representation addresses several practical problems in graphics: smooth geomorphing of level-of-detail approximations, progressive transmission, mesh compression, and selective refinement. In addition, we present a new mesh simplification procedure for constructing a PM representation from an arbitrary mesh. The goal of this optimization procedure is to preserve not just the geometry of the original mesh, but more importantly its overall appearance as defined by its discrete and scalar appearance attributes such as material identifiers, color values, normals, and texture coordinates. We demonstrate construction of the PM representation and its applications using several practical models.

We construct smooth parameterizations of irregular connectivity triangulations of arbitrary genus 2-manifolds. Our algorithm uses hierarchical simplification to efficiently induce a parameterization of the original mesh over a base domain consisting of a small number of triangles. This initial parameterization is further improved through a hierarchical smoothing procedure based on Loop subdivision applied in the parameter domain. Our method supports both fully automatic and user constrained operations. In the latter, we accommodate point and edge constraints to force the align- # wailee@cs.princeton.edu + wim@bell-labs.com # ps@cs.caltech.edu cowsar@bell-labs.com dpd@cs.princeton.edu ment of iso-parameter lines with desired features. We show how to use the parameterization for fast, hierarchical subdivision connectivity remeshing with guaranteed error bounds. The remeshing algorithm constructs an adaptively subdivided mesh directly without first resorting to uniform subdivision followed by subsequent sparsification. It thus avoids the exponential cost of the latter. Our parameterizations are also useful for texture mapping and morphing applications, among others.

We describe a multiresolution representation for meshes based on subdivision. Subdivision is a natural extension of the existing patch-based surface representations. At the same time subdivision algorithms can be viewed as operating directly on polygonal meshes, which makes them a useful tool for mesh manipulation. Combination of subdivision and smoothing algorithms of Taubin [26] allows us to construct a set of algorithms for interactive multiresolution editing of complex meshes of arbitrary topology. Simplicity of the essential algorithms for re nement and coarsi cation allows to make them local and adaptive, considerably improving their efficiency. We have built a scalable interactive multiresolution editing system based on such algorithms.

This paper presents a technique for adapting existing motion of a human-like character to have the desired features that are specified by a set of constraints. This problem can be typically formulated as a spacetime constraint problem. Our approach combines a hierarchical curve fitting technique with a new inverse kinematics solver. Using the kinematics solver, we can adjust the configuration of an articulated figure to meet the constraints in each frame. Through the fitting technique, the motion displacement of every joint at each constrained frame is interpolated and thus smoothly propagated to frames. We are able to adaptively add motion details to satisfy the constraints within a specified tolerance by adopting a multilevel B-spline representation which also provides a speedup for the interpolation. The performance of our system is further enhanced by the new inverse kinematics solver. We present a closed-form solution to compute the joint angles of a limb linkage. This analytical m...

Wavelets have been making an appearance in many pure and applied areas of science and engineering. Computer graphics with its many and varied computational problems has been no exception to this rule. In these notes we will attempt to motivate and explain the basic ideas behind wavelets and what makes them so successful in application areas. The main

Normal meshes are new fundamental surface descriptions inspired by differential geometry. A normal mesh is a multiresolution mesh where each level can be written as a normal offset from a coarser version. Hence the mesh can be stored with a single float per vertex. We present an algorithm to approximate any surface arbitrarily closely with a normal semi-regular mesh. Normal meshes can be useful in numerous applications such as compression, filtering, rendering, texturing, and modeling.

Wavelets are a powerful tool for planar image processing. The resulting algorithms are straightforward, fast, and efficient. With the recently developed spherical wavelets this framework can be transposed to spherical textures. We describe a class of processing operators which are diagonal in the wavelet basis and which can be used for smoothing and enhancement. Since the wavelets (filters) are local in space and frequency, complex localized constraints and spatially varying characteristics can be incorporated easily. Examples from environment mapping and the manipulation of topography/bathymetry data are given.

A whole variety of different techniques for simulating global illumination in virtual environments have been developed over recent years. Each technique, including Radiosity, Monte-Carlo ray- or photon tracing, and directional-dependent Radiance computations, is best suited for simulating only some special case environments. None of these techniques is currently able to efficiently simulate all important lighting effects in non-trivial scenes. In this paper, we describe a new approach for efficiently combining different global illumination algorithms to yield a composite lighting simulation: Lighting Networks. Lighting Networks can exploit the advantages of each algorithm and can combine them in such a way as to simulate lighting effects that could only be computed at great costs by any single algorithm. Furthermore, this approach allows a user to configure the Lighting Network to compute only specific lighting effects that are important for a given task, while avoiding a costly simulation of the full global illumination in a scene. We show how the light paths computed by a Lighting Network can be described using regular expressions. This mapping allows us to analyze the composite lighting simulation and ensure completeness and redundant-free computations. Several examples demonstrate the advantages and unique lighting effects that can be obtained using this technique. 1

er In this thesis, we investigate the computational methods for both diffuse and general reflections in realistic image synthesis and propose two new approaches: the overrelaxation solution and the Bernstein polynomial solution. One of the major concerns with the radiosity method is its expensive computing time and memory requirements. In this thesis, we analyze the convergence behavior of the progressive refinement radiosity method and propose two overrelaxation algorithms: the gathering and shooting solution and the positive overshooting solution. We modify the conventional shooting method to make the optimal use of the visibility information computed in each iteration. Based on a concise record of the history of the unshot light energy distribution, a solid convergence speed-up is achieved. Though a great effort has been made to extend the radiosity method to accommodate general non-diff...