Advances in 3D scanning technologies have enabled the practical creation of meshes with hundreds of millions of polygons. Traditional algorithms for display, simplification, and progressive transmission of meshes are impractical for data sets of this size. We describe a system for representing and progressively displaying these meshes that combines a multiresolution hierarchy based on bounding spheres with a rendering system based on points. A single data structure is used for view frustum culling, backface culling, level-of-detail selection, and rendering. The representation is compact and can be computed quickly, making it suitable for large data sets. Our implementation, written for use in a large-scale 3D digitization project, launches quickly, maintains a user-settable interactive frame rate regardless of object complexity or camera position, yields reasonable image quality during motion, and refines progressively when idle to a high final image quality. We have demonstrated the system on scanned models containing hundreds of millions of samples.

Modeling arbitrary real objects is difficult and rendering textured models typically does not result in realistic images. We describe a new method for displaying scanned real objects, called view-based rendering. The method takes as input a collection of colored range imagescovering the objectand creates a collection of partial object models. These partial models are rendered separately using traditional graphics hardware and blended together using various weights and soft z-buffering. We demonstrate interactive viewing of real, non-trivial objects that would be difficult to model using traditional methods.

Interactive rendering requires rapid visual feedback. The render cache is a new method for achieving this when using high-quality pixel-oriented renderers such as ray tracing that are usually considered too slow for interactive use. The render cache provides visual feedback at a rate faster than the renderer can generate complete frames, at the cost of producing approximate images during camera and object motion. The method works both by caching previous results and reprojecting them to estimate the current image and by directing the renderer's sampling to more rapidly improve subsequent images. Our

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We present a method for interactive rendering of large outdoor scenes. Complex polygonal plant models and whole plant populations are represented by relatively small sets of point and line primitives. This enables us to show landscapes faithfully using only a limited percentage of primitives. In addition, a hierarchical data structure allows us to smoothly reduce the geometrical representation to any desired number of primitives. The scene is hierarchically divided into local portions of geometry to achieve large reduction factors for distant regions. Additionally, the data reduction is adapted to the visual importance of geometric objects. This allows us to maintain the visual fidelity of the representation while reducing most of the geometry drastically. With our system, we are able to interactively render very complex landscapes with good visual quality.

We present a new sampling method for procedural and complex geometries, which allows interactive point-based modeling and rendering of such scenes. For a variety of scenes, object-space point sets can be generated rapidly, resulting in a sufficiently dense sampling of the final image. We present an integrated approach that exploits the simplicity of the point primitive. For procedural objects a hierarchical sampling scheme is presented that adapts sample densities locally according to the projected size in the image. Dynamic procedural objects and interactive user manipulation thus become possible. The same scheme is also applied to on-the-fly generation and rendering of terrains, and enables the use of an efficient occlusion culling algorithm. Furthermore, by using points the system enables interactive rendering and simple modification of complex objects (e.g., trees). For display, hardware-accelerated 3-D point rendering is used, but our sampling method can be used by any other point-rendering approach.

Figure 1: Our method captures and renders existing trees from photographs, by estimating opacity in a volume, then generating and displaying view-dependent textures attached to cells of the volume. (a) One of the original photographs of an oak. (b) The α mask used for the opacity estimation. Two cross slices of the resulting opacity are shown in (c). A synthetic image of the original view, using our view-dependent rendering, is shown in (d). Textures are attached to billboards in cells of the volume and are generated based on estimated opacity. Reconstructing and rendering trees is a challenging problem due to the geometric complexity involved, and the inherent difficulties of capture. In this paper we propose a volumetric approach to capture and render trees with relatively sparse foliage. Photographs of such trees typically have single pixels containing the blended projection of numerous leaves/branches and background. We show how we estimate opacity values on a recursive grid, based on alphamattes extracted from a small number of calibrated photographs of a tree. This data structure is then used to render billboards attached to the centers of the grid cells. Each billboard is assigned a set of view-dependent textures corresponding to each input view. These textures are generated by approximating coverage masks based on opacity and depth from the camera. Rendering is performed using a view-dependent texturing algorithm. The resulting volumetric tree structure has low polygon count, permitting interactive rendering of realistic 3D trees. We illustrate the implementation of our system on several different real trees, and show that we can insert the resulting model in virtual scenes.

This paper describes the successful combination of pre-generated and dynamically updated image-based representations to accelerate the visualization of complex virtual environments. We introduce a new type of impostor, which has the desirable property of limiting de-occlusion errors to a user-specified amount. This impostor, composed of multiple layers of textured meshes, replaces the distant geometry and is much faster to draw. It captures the relevant depth complexity in the model without resorting to a complete sampling of the scene. We show that layers can be dynamically updated during visualization. This guarantees bounded scene complexity in each frame and also exploits temporal coherence to improve image quality when possible. We demonstrate the strengths of this approach in the context of city walkthroughs.

Interactive walkthrough applications require detailed 3D models to give users a sense of immersion in an environment. Traditionally these models are built using computer-aided design tools to define geometry and material properties. But creating detailed models is time-consuming and it is also difficult to reproduce all geometric and photometric subtleties of real-world scenes. Computer vision attempts to alleviate this problem by extracting geometry and photogrammetry from images of the realworld scenes. However, these models are still limited in the amount of detail they recover.

Abstract. The goal of this paper is the interactive rendering of 3D trees covering a landscape, with shading and shadows consistent with the lighting conditions. We propose a new IBR representation, consisting of a hierarchy of Bidirectional Textures, which resemble 6D lightfields. A hierarchy of visibility cube-maps is associated to this representation to improve the performance of shadow calculations. An example of hierarchy for a given tree can be a small branch plus its leaves (or needles), a larger branch, and the entire tree. A Bidirectional Texture (BT) provides a billboard image of a shaded object for each pair of view and light directions. We associate a BT for each level of the hierarchy. When rendering, the appropriate level of detail is selected depending on the distance of the tree from the viewpoint. The illumination reaching each level is evaluated using a visibility cube-map. Thus, we very efficiently obtain the shaded rendering of a tree with shadows without loosing details, contrary to mesh simplification methods. We achieved 7 to 20 fps fly-throughs of a scene with 1000 trees. Keywords: Real-time rendering, natural scenes, forests, IBR, levels of detail, billboards