We propose a highly memory-efficient representation for modeling and rendering urban buildings composed predominantly of rectangular block structures, which can be used to completely or partially represent most modern buildings. With the proposed representation, the data size required for modeling most buildings is more than two orders of magnitude less than using the conventional mesh representation. In addition, it substantially reduces the dependency on conventional texture maps, which are not space-efficient for defining visual details of building facades. The proposed representation can be stored and transmitted as images and can be rendered directly without any mesh reconstruction. A ray-casting based shader has been developed to render buildings thus represented on the GPU with a high frame rate to support interactive fly-by as well as street-level walk-through. Comparisons with standard geometric representations and recent urban modeling techniques indicate the proposed representation performs well when viewed from a short and long distance.

Abstract Image space photon mapping has the advantage of simple implementation on GPU without pre‐computation of complex acceleration structures. However, existing approaches use only a single image for tracing caustic photons, so they are limited to computing only a part of the global illumination effects for very simple scenes. In this paper we fully extend the image space approach by using multiple environment maps for photon mapping computation to achieve interactive global illumination of dynamic complex scenes. The two key problems due to the introduction of multiple images are 1) selecting the images to ensure adequate scene coverage; and 2) reliably computing ray‐geometry intersections with multiple images. We present effective solutions to these problems and show that, with multiple environment maps, the image‐space photon mapping approach can achieve interactive global illumination of dynamic complex scenes. The advantages of the method are demonstrated by comparison with other existing interactive global illumination methods.

Coarse piecewise linear approximation of surfaces causes undesirable polygonal appearance of silhouettes. We present an efficient method for smoothing the silhouettes of coarse triangle meshes using efficient 3D curve reconstruction and simple local re-meshing. It does not assume the availability of a fine mesh and generates only moderate amount of additional data at run time. Furthermore, polygonal feature edges are also smoothed in a unified framework. Our method is based on a novel interpolation scheme over silhouette triangles and this ensures that smooth silhouettes are faithfully reconstructed and always change continuously with respect to continuous movement of the view point or objects. We speed up computation with GPU assistance to achieve real-time rendering of coarse meshes with the smoothed silhouettes. Experiments show that this method outperforms previous methods for silhouette smoothing.

Shares some experience in designing a practical walkthrough system for indoor environments. We discuss issues from the design of efficient utility programs for building 3D models to the design of a walkthrough engine. Our utility programs allow the creation of the interior of a several-storied building in a few man-days. We also propose several rendering speedup techniques implemented in our walkthrough system. Tests have been carried out to benchmark the amount of speedup brought about by different techniques. One of these techniques, called dynamic visibility, proves to be more efficient than existing standard visibility preprocessing methods.