This paper describes VolumePro, the world's first single-chip realtime volume rendering system for consumer PCs. VolumePro implements ray-casting with parallel slice-by-slice processing. Our discussion of the architecture focuses mainly on the rendering pipeline and the memory organization. VolumePro has hardware for gradient estimation, classification, and per-sample Phong illumination. The system does not perform any pre-processing and makes parameter adjustments and changes to the volume data immediately visible. We describe several advanced features of VolumePro, such as gradient magnitude modulation of opacity and illumination, supersampling, cropping and cut planes. The system renders 500 million interpolated, Phong illuminated, composited samples per second. This is sufficient to render volumes with up to 16 million voxels (e.g., 256 3 ) at 30 frames per second.

Many operating system designs can be placed into one of two very rough categories, depending upon how they implement and use the notions of process and synchronization. One category, the "Message-oriented System," is characterized by a relatively small, static number of processes with an explicit message system for communicating among them. The other category, the "Procedure-oriented System," is characterized by a large, rapidly changing number of small processes and a process synchronization mechanism based on shared data.In this paper, it is demonstrated that these two categories are duals of each other and that a system which is constructed according to one model has a direct counterpart in the other. The principal conclusion is that neither model is inherently preferable, and the main consideration for choosing between them is the nature of the machine architecture upon which the system is being built, not the application which the system will ultimately support.

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Surgical simulation has many applications in medical education, surgical training, surgical planning, and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing, or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3D Magnetic Resonance Imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force feedback device. To be published in Journal of Medical Image Analysis, December, 1997.This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy i n whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories of Cambridge, Massachusetts; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories. All rights reserved. Copyright © Mitsubishi Electric Information AbstractSurgical simulation has many applications in medical education, surgical training, surgical planning, and intra-operative assistance. However, extending current surfacebased computer graphics methods to model phenomena such as the deformation, cutting, tearing, or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3D Magnetic Resonance Imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force feedback device.

The Pilot operating system provides a single-user, single-language environment for higher level software on a powerful personal computer. Its features include virtual memory, a large "flat" file system, streams, network communication facilities, and concurrent programming support. Pilot thus provides rather more powerful facilities than are normally associated with personal computers. The exact facilities provided display interesting similarities to and differences from corresponding facilities provided in large multi-user systems. Pilot is implemented entirely in Mesa, a highlevel system programming language. The modularization of the implementation displays some interesting aspects in terms of both the static structure and dynamic interactions of the various components.

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This paper describes shear-image order ray casting, a new method for volume rendering. This method renders sampled data in three dimensions with image quality equivalent to the best of ray-per-pixel volume rendering algorithms (full image order), while at the same time retaining computational complexity and spatial coherence near to that of the fastest known algorithm (shear-warp). In shear-image order, as in shear-warp, the volume data set is resampled along slices parallel to a face of the volume. Unlike shear-warp, but like the texture-based methods, rays are cast through the centers of pixels of the image plane and sample points are at the intersections of rays with each slice. As a result, no post-warp step is required. Unlike texture methods, which realize shear and warp by transformations in a commodity graphics system, the shear-image ray casting methods use a new factorization that preserves memory and interpolation efficiency. In addition, a method is provided for accurately and efficiently embedding conventional polygon graphics and other objects into volumes. Both opaque and translucent polygons are supported.We also describe a method, included in shear-image order but applicable to other algorithms, for rendering anisotropic and sheared volume data sets directly with correct lighting.The shear-image order method has been implemented in the VolumePro™ 1000, a single chip real-time volume rendering engine capable of processing volume data at a pipeline rate of 10 9 samples per second. Figure 1 on the color page shows a shearimage order gallery of volumes rendered with different translucency, lighting, and some embedded geometry.