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Now showing 1 - 4 of 4
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    Image-Based Rendering of Surfaces from Volume Data
    (The Eurographics Association, 2001) Chen, Baoquan; Kaufman, Arie; Tang, Qingyu; K. Mueller and A. Kaufman
    We present an image-based rendering technique to accelerate rendering of surfaces from volume data. We cache the fully volume rendered image (called keyview) and use it to generate novel views without ray-casting every pixel. This is achieved by first constructing an underlying surface model of the volume and then texture mapping the keyview onto the geometry.When the novel view moves slightly away from the keyview, most of the original visible regions in the keyview are still visible in the novel view. Therefore, we only need to cast rays for pixels in the newly visible regions, which usually occupy only a small portion of the whole image, resulting in a substantial speedup. We have applied our technique to a virtual colonoscopy system and have obtained an interactive navigation speed through a 512<sup>3</sup> size patient colon. Our experiments demonstrate an average of an order of magnitude speedup over that of traditional volume rendering, compromising very little on image quality.
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    Accelerating Voxel-Based Terrain Rendering with Keyframe-Free Image-Based Rendering
    (The Eurographics Association, 2001) Qin, Jiafa; MingWan,; Qu, Huamin; Kaufman, Arie; K. Mueller and A. Kaufman
    We propose a voxel-based terrain rendering method which incorporates a novel keyframe-free image-based rendering algorithm and a new heuristic ray coherence raycasting algorithm. The current image is generated by warping the previous image with a revised 3D warping algorithm and filling holes by raycasting, accelerated by ray coherence and multiresolution ray traversal. This method not only achieves good performance, but also allows arbitrary viewing directions. We further accelerate the rendering with multiprocessor parallelism and have achieved a real-time rendering rate of 30Hz on a 16-processor SGI Power Challenge.
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    Real-Time Volume Rendering for Virtual ColonoscopyS
    (The Eurographics Association, 2001) Li, Wei; Kaufman, Arie; Kreeger, Kevin; K. Mueller and A. Kaufman
    We present a volume rendering system that is capable of generating high-quality images of large volumetric data (e.g., 512<sup>3</sup>) in real time (30 frames or more per second). The system is particularly suitable for applications that generate densely occluded scenes of large data sets, such as virtual colonoscopy. The central idea is to divide the volume into sets of axis-aligned slabs. The union of the slabs approximates the shape of a colon. We render sub-volumes enclosed by the slabs and blend the slab images. We use the slab structure to accelerate volume rendering in various aspects. First, empty voxels outside the slabs are skipped. Second, fast view-volume clipping and occlusion culling are applied based on the slabs. Third, slab images are reused for nearby viewpoints. In addition, the slabs can be created very efficiently and they can be used to approximate perspective rendering with parallel projection, so that our system can benefit from fast parallel projection hardware and algorithms. We use image-warping to reduce the artifacts due to the approximation.
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    Two-Pass Image and Volume Rotation
    (The Eurographics Association, 2001) Chen, Baoquan; Kaufman, Arie; K. Mueller and A. Kaufman
    We present a novel two-pass approach for both 2D image and 3D volume rotation. Each pass is a pseudo shear. However, it has a similar regularity as a pure shear in that a beam remains rigid while being sheared. Furthermore, the 3D pseudo shear guarantees that beams within one major axis slice remain in the same directional plane after the shearing. These properties make it feasible to implement the pseudo shears on a multi-pipelined hardware or a massively parallel machine. Compared with the existing decompositions, ours offer a minimum number of shears to realize an arbitrary 3D rotation. Our decomposition also preserves the image/volume quality by guaranteeing no minification for the first pass shear.