Abstract: Most computer graphics pictures have been computed all at once, so that the rendering program takes care of all computations relating to the overlap of objects. There are several applications, howe...

Abstract: A controllability measure in terms of the distance between a system and the set of uncontrollable systems is developed. Some properties of a minimal disturbance, rendering a system noncontrollable, are given.

Abstract: This paper describes the hardware architecture and the employed algorithm of a parallel processor system for three-dimensional color graphics. The design goal of the system is to generate realistic images of three-dimensional environments on a raster-scan video display in real-time. In order to achieve this goal, the system is constructed as a two-level hierarchical multi-processor system which is particularly suited to incorporate scan-line algorithm for hidden surface elimination. The system consists of several Scan-Line Processors (SLPs), each of which controls several slave PiXel Processors (PXPs). The SLP prepares the specific data structure relevant to each scan line, while the PXP manipulates every pixel data in its own territory. Internal hardware structures of the SLP and the PXP are quite different, being designed for their dedicated tasks.This system architecture can easily execute scan-line algorithm in parallel by partitioning the entire image space and allotting one processor element to each partition. The specific partition scheme and some new data structures are introduced to exploit as much parallelism as possible. In addition, the scan-line algorithm is extended to include smooth-shading and anti-aliasing with the aim of rendering more realistic images. These two operations are performed on a per-scan-line basis so as to preserve scan-line and span coherence.Performance estimation of the system shows that a typical system consisting of 8 SLPs and 8×8 PXPs can generate, in every 1/15th of a second, the shadowed image of a three-dimensional scene containing about 200 polygons.

Abstract: This paper presents computational techniques using which subdivision algorithms may be devised for the processing (rendering, intersection detection, silhouette detection) of parametrically defined surfaces. These algorithms work by subdividing surface patches until they are simple enough for direct handling. For example, planar surface patches can be handled analytically. For interference it is necessary to box the surface as well. The computational techniques presented are essentially for efficient computation of surface properties needed by the processing tasks. The three properties considered are: (1) Euclidean bounds: this is done by working in extrema in x, y, and z over the patch; (2) planarity estimate: this test is defined in terms of the linearity of constituent curves; (3) Local visibility: which says whether a patch is totally visible, invisible, or partially visible from a given viewpoint. Rendering algorithms make use of this information. This too is done by working in extrema of the visibility function. All the techniques are based on the parametric form of the surface representation. The class of surfaces that can be handled by these techniques is very large, basically C2 continuous surfaces. A class of surfaces known as product surfaces is specially introduced as the above methods are extremely efficient for this class. Application of these methods to bicubic surfaces is also discussed.

Abstract: When young children draw a scene in which one object partially occludes another, they often depict hidden features of the occluded object by rendering the nearer object transparent. This may signify a motive to produce drawings that are informative. Three experiments are reported in which a simple paradigm is employed to consider this possible basis of transparency drawing. Experiment 1 established a gradual decrease in the use of this device across the 5–7-year age range. Its occurrence could not be ascribed to a simple lack of graphic skill and it was not readily inhibited by stronger perceptual marking of scene boundaries. The extent to which children were purposefully producing informative drawings was evaluated in Expts 2 and 3. Because an increase in occluded information actually served to inhibit transparencies, it is argued that they need not reflect such a communicative attitude. An alternative account is proposed whereby drawing decisions are guided, sometimes inappropriately, by the structure of cognitive representations children form of scenes. Transparencies signify a failure to anticipate certain graphic ambiguities thereby generated. However, they may be inhibited if the geometry of a particular scene forces the child to confront such ambiguity at the outset of drawing.

Abstract: Stochastic modeling has found uses so far mainly for expensive very realistic graphics display. The cost of rendering is not intrinsic to the technique, but mainly due to the high resolution and the sophisticated display techniques which accompany it. We describe here a basic tool for a less expensive approach to stochastic modeling which is designed for a more “down to earth” type of application, and brings the display of stochastic models nearer to real-time.A special purpose board for stochastic interpolation has been built, which can generate an array of up to 129×129 12 bit stochastic values to be used by the rest of the display system as a texture source, or for more elaborate algorithms. The board functions as a coprocessor in a traditional frame buffer system, and includes a micro-coded bit-slice processor, a multiplier, special hardware to generate uniformly distributed random numbers, memory to store a look-up table for random numbers with the required distribution, and two buffers for the resulting arrays.The current implementation generates values at less than 4 microseconds per point, and in conjunction with a standard graphics processor can display nearly 10000 stochastic points in real-time, or can update a full screen of stochastic values in less than one second. Illustrations are given of the output of the board and of pictures and animations generated with it.

Abstract: A method of adaptively controlling the time of rendering the individual controlled devices (1-6) of a controllable power conversion bridge (10) includes the sensing (26) of the instant in time at which the current from the bridge (10) to a load (16) becomes discontinuous. From the time of this sensing, the time period to a predetermined time such as a normally calculated time of rendering the controlled devices conductive is derived. This time period is then multiplied by a multiplier and the resultant product is combined with the predetermined time to provide an actual time of rendering the controlled devices conductive.

Abstract: Digital Scene Simulation is Digital Productions' philosophy for creating visual excellence in computer-generated imagery and simulation. The approach it advocates requires the use of powerful hardware, sophisticated software, and top creative talent. With a CRAY supercomputer at the heart of its computer network and its own proprietary image rendering and simulation software, Digital Productions is revolutionizing state-of-the-art computer graphics. At the forefront of computer graphics technology, Digital Productions is redefining traditional methods of visual communications and creating new forms of self-expression, instruction, and entertainment.

Abstract: We briefly survey the major thrusts of computer graphics activities, examining trends and topics rather than offering a comprehensive survey of all that is happening. The directions of professional activities, hardware, software, and algorithms are outlined. Within hardware we examine workstations, personal graphics systems, high performance systems, and low level VLSI chips; within software, standards and interactive system design; within algorithms, visible surface rendering and shading, three-dimensional modeling techniques, and animation. Note: This paper was presented at Eurographics'84 in Copenhagen, Denmark. Disciplines Computer Engineering | Computer Sciences Comments University of Pennsylvania Department of Computer and Information Science Technical Report No. MSCIS-85-32. This technical report is available at ScholarlyCommons: http://repository.upenn.edu/cis_reports/994 The Computer Graphics Scene in the United States Norman I. Badler MS-CIS-SS-32 Department of Computer and Information Science Moore School/D2 University of Pennsylvania Philadelphia, PA 19104

Abstract: The present invention relates to a microwave hybrid ring. In addition to a conventional entrance path E, two exit paths S1 and S2 and a difference path D1, the hybrid ring includes a second difference path D2 rendering the entrance path E symmetric. The invention applies in particular to a power divider used in producing power distributors for supplying multiple primary source networks.

Abstract: An electronic system for the enhancement of video image contrast in real time is described and examples of its application are shown. The system achieves high speed and flexibility through the use of microprocessor-controlled digital hardware, rendering it useful as an interactive tool for image processing at relatively low cost. Several stretching techniques are demonstrated, including an interactive method whereby an elaborate contrast transfer function may be specified manually.

Abstract: The method for forming a message composed of characters, in particular alphanumeric, comprises a keyboard 2 having available a number of means of selection 6 and means for rendering the said characters 3 perceptible. It includes the following operations: some at least of the means of selection 6 are assigned a number of predetermined characters, and when any one of the said means of selection 6 is actuated the characters which are associated therewith are rendered perceptible cyclically, then the user is enabled to check the chosen character when the latter is perceived. Use in particular in a bidirectional device for radio wave telecommunication between a fixed central set and mobile peripheral sets.

Abstract: Do you want to become more confident sketching buildings with a pen or pencil? How about refining your skill in rendering the projects you are designing? Whether you are a designer, an architect, an artist or a student interested in architecture, this volume, filled with a broad range of sketching and rendering techniques and styles, offers the complete intermediate level of instruction you need. Profusely illustrated with 325 illustrations, "Architectural Sketching and Rendering" is required reading if you want to learn how to create your own successful drawings.

Abstract: This method for modeling and rendering landscapes combines contour line descriptions and random data into a linear octree data structure. Two-dimensional data is mapped onto the surface and underlying volumes.

Abstract: The generation of realistic imagery relies upon an adequate amount of visual detail in the image. A method of dynamically changing the amount of detail displayed as an object gets closer to the eyepoint is needed to maintain proper level of detail. One method is to establish a hierarchy of object descriptions which represent an object at various amounts of detail. This hierarchy can then be accessed to present the correct amounts of detail. When an object is moving relative to the eyepoint, a method of changing between levels in the description hierarchy is needed. The transition can be done instantaneously, or over a certain distance or time range. This blending is done using transparency or pixel coverage. A software system which manages object description hierarchies is described. This system includes a data generation system which creates object descriptions at various levels of complexity, object simplifiers which take a detailed object description and perform automatic simplification, an object editor which allows users to easily manipulate object descriptions, an object description verification program which checks for inconsistencies in an object description, the necessary control programs to decide when and how to change between levels in the hierarchy, and a display program which can blend two object descriptions into one image. Finally, the results of using this system to create an animated sequence of a submarine docking maneuver are reported. A savings of approximately 70% in computation time is achieved through the proper management of detail.

Abstract: Ray tracing is a widely used method for producing realistic computer generated images. Ray tracing involves firing an imaginary ray from a view point, through a point on an image plane, into a three dimensional scene. The intersections of the ray with the objects in the scene determines what is visible at the point on the image plane. This process must be repeated many times, once for each point (commonly called a pixel) in the image plane. A typical image contains more than a million pixels making this process computationally expensive. A traditional ray tracing program processes one ray at a time. In such a serial approach, as much as ninety percent of the execution time is spent computing the intersection of a ray with the surface in the scene. With the CYBER 205, many rays can be intersected with all the bodies im the scene with a single series of vector operations. Vectorization of this intersection process results in large decreases in computation time. The CADLAB's interest in ray tracing stems from the need to produce realistic images of mechanical parts. A high quality image of a part during the design process can increase the productivity of the designer by helping him visualize the results of his work. To be useful in the design process, these images must be produced in a reasonable amount of time. This discussion will explain how the ray tracing process was vectorized and gives examples of the images obtained.

Abstract: Computer image synthesis is a powerful and flexible tool for producing film and video animation. To use it, one “tells the computer” how to make an image and then goes away for a while. Images produced by the simplest methods have a cartoonlike appearance, while advanced techniques will generate pictures that cannot be immediately distinguished from photographs of real scenes. Although computer-generated images have long been used for flight training and some scientific and engineering applications, they are increasingly being used for special effects in the advertising and entertainment fields. In spite of this growing application, the complexity of image synthesis techniques continues to intimidate most people. The purpose of this paper is to demystify the image-making process without understating the difficulty that it presents.

Abstract: Several straightforward techniques for displaying arbitrary solids of the sort encountered in the life sciences are presented, all variations of simple three-dimensional scatter plots. They are all targeted for a medium cost raster display (an AED-5l2 has been used here). Practically any host computer may be used to implement them. All techniques are broadly applicable and were implemented as Master Degree projects. The major hardware constraint is data transmission speed, and this is met by minimizing the amount of graphical data, ignoring enhancement of the data, and using terminal scan-conversion and aspect firmware wherever possible. Three simple rendering techniques and the use of several graphics cues are described.

Abstract: The A-buffer (anti-aliased, area-averaged, accumulation buffer) is a general hidden surface mechanism suited to medium scale virtual memory computers. It resolves visibility among an arbitrary collection of opaque, transparent, and intersecting objects. Using an easy to compute Fourier window (box filter), it increases the effective image resolution many times over the Z-buffer, with a moderate increase in cost. The A-buffer is incorporated into the REYES 3-D rendering system at Lucasfilm and was used successfully in the “Genesis Demo” sequence in Star Trek II.

Abstract: A pragmatic approach is taken to develop an algorithm that combines an existing shadowing method with a popular visible surface rendering technique, called a depth buffer, to generate soft shadows resulting from light sources of finite extent. The method extends F. Crow's shadow volume algorithm (1977) to produce multiple shadows overlapped to yield the characteristic soft edges of a shadow penumbra.