The fast identification of shadow regions due to area light sources is necessary for realistic rendering and for discontinuity meshing for global illumination. A new shadow-determination algorithm is presented that uses a data structure, called a backprojection, to represent the visible portion of a light source from any point in the scene. A complete discontinuity meshing algorithm is described for polyhedral scenes and area light sources, which includes an important class of light/geometry interactions that have not been implemented before. A fast incremental algorithm for computing backprojections is also described. The use of spatial subdivision, and heuristics based on computed statistics of typical scenes, results in efficient mesh and backprojection computation. Results of the implementation show that the use of the backprojection and discontinuity meshing permits accelerated high-quality rendering of shadows using both ray-casting and polygon-rendering with interpolants. CR C...

this article, we emphasize practical issues; an earlier survey by Bern and Eppstein [24] emphasized theoretical results. Although there is inevitably some overlap between these two surveys, we intend them to be complementary.

Appeared in Computational Geometry -- Theory and Applications 13, 1999, 65-90. Software design solutions are presented for combinatorial data structures, such as polyhedral surfaces and planar maps, tailored for program libraries in computational geometry. Design issues considered are flexibility, time and space efficiency, and ease-of-use. We focus on topological aspects of polyhedral surfaces and evaluate edge-based representations with respect to our design goals. A design for polyhedral surfaces in a halfedge data structure is developed following the generic programming paradigm known from the Standard Template Library STL for C++. Connections are shown to planar maps and face-based structures. Key words: Library design; Generic programming; Combinatorial data structure; Polyhedral surface; Halfedge data structure 1 Introduction Combinatorial structures, such as planar maps, are fundamental in computational geometry. In order to be useful in practice, a solid library for compu...

Design solutions for a program library are presented for combinatorial data structures in computational geometry, such as planar maps and polyhedral surfaces. Design issues considered are genericity, flexibility, time and space efficiency, and ease-of-use. We focus on topological aspects of polyhedral surfaces. Edge-based representations for polyhedrons are evaluated with respect to the design goals. A design for polyhedral surfaces in a halfedge data structure is developed following the generic programming paradigm known from the Standard Template Library STL for C++. Connections are shown to planar maps and face-based structures managing holes in facets. 1 Introduction Combinatorial structures, such as planar maps, are fundamental in computational geometry. In order to use computational geometry in practice, a solid library must provide generic and flexible solutions as one of its fundamental cornerstones. Other design criteria are time and space efficiency. Ease-of-use is necessar...

Our work in the area of non-photo-realistic rendering (NPR) focuses on visualising 3D models in a cartoon rendering style: the geometrical objects are internally coloured using two or three colours, while simultaneously using an explicit outline. Many NPR techniques are timeconsuming processes, whereas we aim at real-time rendering performance on mainstream graphics PC hardware without losing a high image quality. Particular emphasis is also put on getting smooth transition borders between the bi-tonal cartoon-colours by applying an object precision triangle subdivision technique. Rapidly finding these transition borders as well as silhouette edges is a topic of a new algorithm. As silhouette lines and light effects are useful indicators for computer vision, this algorithm also looks interesting for applications in that field.

vii Acknowledgements viii 1. Introduction 1 1.1 What is Computer Sculpting? : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1.2 The Free-Form Design Problem in Computer Graphics : : : : : : : : : : : : 2 1.3 Contributions of this Thesis : : : : : : : : : : : : : : : : : : : : : : : : : : : 4 2. Related Work 6 2.1 Polygonal Mesh Sculpting : : : : : : : : : : : : : : : : : : : : : : : : : : : : 6 2.2 Virtual Tools : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9 2.3 Other Approaches to Sculpting : : : : : : : : : : : : : : : : : : : : : : : : : 11 2.3.1 FFD-Based Systems : : : : : : : : : : : : : : : : : : : : : : : : : : : 11 2.3.2 Hierarchical B-Spline Refinement : : : : : : : : : : : : : : : : : : : : 12 2.3.3 2 1/2 D Paint Systems : : : : : : : : : : : : : : : : : : : : : : : : : : 13 3. Features of the System 14 3.1 Polygonal Mesh Modeling : : : : : : : : : : : : : : : : : : : : : : : : : : : : 14 3.2 Mesh Refinement Operations : : : : : : : : : : : : : ...

The fast identification of shadow regions due to area light sources is necessary for realistic rendering and for discontinuity meshing for global illumination. A new shadow-determination algorithm is presented that uses a data structure, called a backprojection, to represent the visible portion of a light source from any point in the scene. A complete discontinuity meshing algorithm is described for polyhedral scenes and area light sources, which includes an important class of light/geometry interactions that have not been implemented before. A fast incremental algorithm for computing backprojections is also described. The use of spatial subdivision, and heuristics based on computed statistics of typical scenes, results in efficient mesh and backprojection computation. Results of the implementation show that the use of the backprojection and discontinuity meshing permits accelerated high-quality rendering of shadows using both ray-casting and polygon-rendering with interpolants.

Abstract not found