Browsing by Subject "Quadtrees"

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    Representing objects as rays, or how to pile up an octree?
    (Elsevier, 1989) Akman, V.; Franklin, Wm. R.
    Quadtrees, octrees, and in general k-trees have established themselves as useful hierarchical data structures in computer graphics, image processing, and solid modeling. A fundamental operation in a system based on k-trees is the construction of a k-tree. Here, we review a new way of doing this operation. Basically, we have invented a method to store an object as a set of rays and an algorithm for converting such a set into a k-tree. (For example, in 3D a ray is a thin parallelepiped.) The algorithm is conceptually simple, works for any k, and piles up, using an approach we call stacking, a k-tree from the rays very fast. It produces a minimal k-tree and does not lead to intermediate storage swell. For large-scale realistic objects, which consist of many thousands of rays, the algorithm debunks the "expensive octree creation" myth. © 1989.
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    Stereoscopic view-dependent visualization of terrain height fields
    (IEEE, 2002) Güdükbay, Uğur; Yilmaz, T.
    Visualization of large geometric environments has always been an important problem of computer graphics. In this paper, we present a framework for the stereoscopic view-dependent visualization of large scale terrain models. We use a quadtree based multiresolution representation for the terrain data. This structure is queried to obtain the view-dependent approximations of the terrain model at different levels of detail. In order not to lose depth information, which is crucial for the stereoscopic visualization, we make use of a different simplification criterion, namely, distance-based angular error threshold. We also present an algorithm for the construction of stereo pairs in order to speed up the view-dependent stereoscopic visualization. The approach we use is the simultaneous generation of the triangles for two stereo images using a single draw-list so that the view frustum culling and vertex activation is done only once for each frame. The cracking problem is solved using the dependency information stored for each vertex. We eliminate the popping artifacts that can occur while switching between different resolutions of the data using morphing. We implemented the proposed algorithms on personal computers and graphics workstations. Performance experiments show that the second eye image can be produced approximately 45 percent faster than drawing the two images separately and a smooth stereoscopic visualization can be achieved at interactive frame rates using continuous multiresolution representation of height fields.