Instant Visibility

Abstract

We present an online occlusion culling system which computes visibility in parallel to the rendering pipeline. We show how to use point visibility algorithms to quickly calculate a tight potentially visible set (PVS) which is valid for several frames, by shrinking the occluders used in visibility calculations by an adequate amount. These visibility calculations can be performed on a visibility server, possibly a distinct computer communicating with the display host over a local network. The resulting system essentially combines the advantages of online visibility processing and region‐based visibility calculations, allowing asynchronous processing of visibility and display operations. We analyze two different types of hardware‐based point visibility algorithms and address the problem of bounded calculation time which is the basis for true real‐time behavior. Our results show reliable, sustained 60 Hz performance in a walkthrough with an urban environment of nearly 2 million polygons, and a terrain flyover.

On error bound estimation for motion prediction

“…In order to show the performance of our method in estimating the error bound in a real application, we have incorporated it into an area-based visibility culling algorithm for virtual walkthrough [17]. With a point-based visibility culling algorithm, a potential visibility set (PVS) is computed for rendering based on a given view point [8].…”

“…With a point-based visibility culling algorithm, a potential visibility set (PVS) is computed for rendering based on a given view point [8]. However, if all occluders visible from a given location (360 o ) are shrinked by an ε-distance, the resulting PVS will be valid even if the viewer moves inside a circular region of radius ε-distance centered at the given location [17]. With such an area-based visibility culling algorithm, we no longer need to compute the PVS at every step as the user navigates in a virtual environment.…”

Stereoscopic urban visualization based on graphics processor unit

“…On-line algorithms calculate the visibility during run-time. 12 However, the scalability is limited if no simplifying assumptions are made. To overcome this, geometry-reduction techniques such as view-dependent simplification schemes can be incorporated.…”

“…1͒. Wonka et al 12 shrink occluders by using a sphere constructed around 2.5-D occluders.In Ref. 16, instead of a sphere, the authors calculate erosion of the occluder using a convex shape, which is the union of the edge convex hulls of the object.…”

Interactive view-dependent rendering with conservative occlusion culling in complex environments

“…Many occlusion culling algorithms have been designed for specialized environments, including architectural models based on cells and portals [Airey et al 1990;Teller 1992;Luebke and Georges 1995] and urban datasets composed of large occluders [Coorg and Teller 1997;Hudson et al 1997;Schaufler et al 2000;Wonka et al 2000;Wonka et al 2001]. These approaches generally precompute a potentially visible set (PVS) for a region.…”