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Item Template-Based Volume Viewing(Blackwell Science Ltd and the Eurographics Association, 1992) Yagel, Roni; Kaufman, ArieWe present an efficient three-phase algorithm for volume viewing that is based on exploiting coherency between rays in parallel projection. The algorithm starts by building a ray-template and determining a special plane for projection - the base-plane. Parallel rays are cast into the volume from within the projected region of the volume on the base-plane, by repeating the sequence of steps specified in the ray-template. We carefully choose the type of line to be employed and the way the template is being placed on the base-plane in order to assure uniform sampling of the volume by the discrete rays. We conclude by describing an optimized software implementation of our algorithm and reporting its performance.Item Image-Based Rendering of Surfaces from Volume Data(The Eurographics Association, 2001) Chen, Baoquan; Kaufman, Arie; Tang, Qingyu; K. Mueller and A. KaufmanWe 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.Item Building a Full Scale VLSI-Based Volume Visualization System(The Eurographics Association, 1990) Bakalash, Reuven; Kaufman, Arie; Xu, Zhong; Richard Grimsdale and Arie KaufmanThe hardware realization of an advanced prototype of the Cube volume visualization system, Cube-3, is presented. The primary hardware component of Cube is a viewing and rendering multiprocessor with distributed 3D voxel memory. Cube-3 design is based on our experience with two earlier prototypes: Cube-1 realized in hard ware using printed circuit board technology and Cube-2 our first custom-designed VLSI implementation. Both prototypes are of reduced-size resolution (163 ) and can generate only orthographic views. Cube-3 is the next generation prototype of a full-scale resolution of 2563 voxels. It has been functionally extended to generate non-orthographic projec tions, 3D real-time transformations, and shading. The ability to project and manipulate volumetric images in real-time is attributed to a unique skewed memory organization, a generalized skewed mapping, a special ray projection bus, a congradient shading tech nique, and a new barrel-shifting mechanism. This paper specifically describes the latter mechanism.Item 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. KaufmanWe 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.Item Cube-4 Implementations on the Teramac Custom Computing Machine(The Eurographics Association, 1996) Kanus, Urs; Meißner, Michael; Straßer, Wolfgang; Pfister, Hanspeter; Kaufman, Arie; Amerson, Rick; Carter, Richard J.; Culbertson, Bruce; Kuekes, Phil; Snider, Greg; Bengt-Olaf Schneider and Andreas SchillingWe present two implementations of the Cube-4 volume rendering architecture on the Teramac custom computing machine. Cube-4 uses a slice parallel ray-casting algorithm that allows for a paral lel and pipelined implementation of ray-casting with tri-linear interpolation and surface normal estimation from interpolated samples. Shading, classification and compositing are part of rendering pipeline. With the partitioning schemes introduced in this paper, Cube-4 is capable of rendering large datasets with a limited number of pipelines. The Teramac hardware simulator at the Hewlett-Packard research laboratories, Palo Alto, CA, on which Cube-4 was implemented, belongs to the new class of custom computing machines. Teramac combines the speed of special-purpose hardware with the flexibility of general-purpose computel's. With Teramac as a development tool we were able to implement in just five weeks working Cube-4 prototypes, capable of rendering for example datasets of 1283 voxels in 0.65 seconds at 0,96 MHz processing frequency. The performance results from these implementations indicate real-time performance for high-resolution data-sets.Item Three Architectures for Volume Rendering(Blackwell Science Ltd and the Eurographics Association, 1995) Hesser, Jurgen; Manner, Reinhard; Knittel, Gunter; Strasser, Wolfgang; Pfister, Hanspeter; Kaufman, ArieVolume rendering is a key technique in scientific visualization that lends itself to significant exploitable parallelism. The high computational demands of real-time volume rendering and continued technological advances in the area of VLSl give impetus to the development of special-purpose volume rendering architectures. This paper presents and characterizes three recently developed volume rendering engines which are based on the ray-casting method. A taxonomy of the algorithmic variants of ray-casting and details of each ray-casting architecture are discussed. The paper then compares the machinefeatures and provides an outlook onfuture developments in the area of volume rendering hardware.Item Real-Time Volume Rendering for Virtual ColonoscopyS(The Eurographics Association, 2001) Li, Wei; Kaufman, Arie; Kreeger, Kevin; K. Mueller and A. KaufmanWe 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.Item Hybrid Volume and Polygon Rendering with Cube Hardware(The Eurographics Association, 1999) Kreeger, Kevin; Kaufman, Arie; A. Kaufmann and W. Strasser and S. Molnar and B.- O. SchneiderWe present two methods which connect today s polygon graphics hardware accelerators to Cube-5 volume rendering hardware, the successor to Cube4 The proposed methods allow mixing of both opaque and translucent polygons with volumes on PC class machines, while ensuring the correct compositing order of all objects. Both implementations connect the two hardware acceleration subsystems at the frame buffer. One shares a common DRAM buffer and one run-length encodes images of thin slabs of polygonal data and then combines them in the Cube composite buffer In both realizations, we take advantage of the predictable ordered access to frame buffer storage that is utilized by Cube-5 and the rest of the family of volume rendering accelerators based on the Cube design.Item PAVLOV: A Programmable Architecture for Volume Processing(The Eurographics Association, 1998) Kreeger, Kevin; Kaufman, Arie; S. N. SpencerWe present a parallel 2D mesh connected architecture with SIMD processing elements. The design allows for real-time volume rendering as well as interactive 30 segmentation and 1D feature extraction. This is possible because the SIMD processing elements are programmable, a feature which also allows the use of many different rendering algorithms. We present an algorithm which, with the addition of hardware resources, provides conflict free access to volume slices along any of the three major axes. The volume access conflict has been the main reason why previous similar architectures could not perform real-time volume rendering. We present the performance of preliminary algorithms on a software simulator of the architecture design.Item A 3-D CELLULAR FRAME BUFFER(The Eurographics Association, 1985) Kaufman, Arie; Bakalash, Reuven; C.E. VandoniA new architecture for storing and processing of threedimensional (3-D) graphics is described, The 3-D objects are discretized and stored in a full 3-D cellular memory of voxels. A 3-D graphics processor scan-converts 3-D geometric objects into the cellular representation. A 3-D frame buffer processor manipulates 3-D cellular sub-boxes and controls 3-D interaction. Displaying 2-D orthographic projections from a given view position and direction is accomplished by a 3-D viewing processor. With this new architecture, there is neither a need for repeatedly scan-converting modified geometric objects nor a need for removing hidden-surfaces.