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Tapestry: An Efficient Mesh-based Display Representation for Interactive Rendering

Simmons, Maryann
Technical Report Identifier: CSD-01-1153
August 2001

Abstract: This thesis introduces the tapestry, an efficient mesh-based display representation, and explores its use for interactive rendering.

Interactive, realistic rendering of complex environments is a longstanding goal in the field of computer graphics. Traditionally, polygon-based hardware rendering pipelines have supported interactive viewing, while off-line global illumination methods have provided high quality imagery. Incorporating both realism and fast display update into a single system, however, continues to pose a challenge. The tapestry display representation is proposed as a means of closing the gap between existing paradigms by incorporating the benefits of point sampling techniques and polygon rendering pipelines into a single interactive framework.

A tapestry is a 2.5D triangle mesh with spherical Delaunay topology that is used as an efficient, view-dependent display representation. The tapestry acts as a cache of rendered point samples. The point samples are used as the vertices of the triangle mesh and can come from any sample generator such as a polygon renderer or ray tracer. The mesh can be rendered from any viewpoint, and the Delaunay condition ensures good quality reconstructions -- even with a sparse sampling. The mesh has 2D topology relative to the viewpoint from which it is generated, enabling efficient mesh construction algorithms. We present robust mesh update algorithms based on geometric constraints. The mesh can be evolved across viewpoints allowing maximal re-use of samples while maintaining the geometric constraints. The tapestry mesh can be rendered rapidly utilizing existing graphics hardware. We introduce new techniques for adaptive sampling and tapestry construction using graphics hardware.

We demonstrate the use of the tapestry as a static display representation in a polygon-based walkthrough environment, and as a dynamic display representation as an interactive front-end for ray-tracing. A new interactive rendering framework based on a fully dynamic tapestry is presented and evaluated. By decoupling the display representation from the sample generator through caching and reconstruction, and by providing an efficient, output-sensitive display representation, the tapestry makes interactive exploration of visually and geometrically complex environments possible even on low-end machines.

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