Showing papers on "Computer graphics published in 1979"

Algorithms for Reporting and Counting Geometric Intersections

Abstract: An interesting class of "geometric intersection problems" calls for dealing with the pairwise intersections among a set of N objects in the plane, These problems arise in many applications such as printed circuit design, architectural data bases, and computer graphics. Shamos and Hoey have described a number of algorithms for detecting whether any two objects in a planar set intersect. In this paper we extend their work by giving algorithms that count the number of such intersections and algorithms that report all such intersections.

An improved illumination model for shaded display

Abstract: To accurately render a scene, global illumination information that affects the intensity of each pixel of the image must be known at the time the intensity is calculated. In a simplified form, this...

3D input for CAAD systems

Abstract: It is often acknowledged that the main advantage of computer aided architectural design (CAAD) systems is that they can be used by architects to quickly and accurately evaluate alternative design solutions using a variety of performance measures which would be too time consuming to apply by hand calculation. To gain the full advantage of interactive CAAD requires the architect to use a computer terminal with graphic capabilities so that he can create and modify his design geometry in a form which can also be directly interpreted by the evaluate routines within the CAAD system. However, it is suggested that it is often difficult for the user of such conventional, graphic, CAAD systems to conceptualise the building being designed by only inspecting and manipulating drawings displayed on the terminal screen. This problem may be accentuated when building users who are not professional architects wish to use a CAAD system so as to participate in the design process. A computerised building block system (BBS) is proposed with which the designer can physically build a model of his design as he would if he was using ‘Lego’ ∗ blocks. Such a physical representation may allow him to evaluate many of the visual and spatial qualities of his design in a more direct way than could be achieved using computer graphics. However, because the electronic system can ‘read’ the arrangement of blocks and input this information into a computer, the user's design can be evaluated with the same performance measures that are used in existing CAAD systems.

A spherical representation of a human body for visualizing movement

Abstract: A three-dimensional human body model for displaying body movements on a computer graphics display is described. The surface of the body model is formed from overlapping spheres, yielding a realistically formed and shaded body image on a raster graphics display. An experimental model consisting of 310 spheres is articulated with 19 joints and 20 body segments. The properties of this model include joints which do not deform during movement, simple hidden surface removal, and efficient collision and contact detection. The model may also be placed in a planar polygon environment, displayed in shaded form, and tested for collisions with the environment. Applications in crash simulation and human movement simulation are indicated.

Data processing system and apparatus for color graphics display

Abstract: A system and apparatus for managing the picture memory of a digital color graphics imaging system, thereby enabling images on a display monitor to be changed efficiently at high rates, and more specifically a control system which comprises a video memory controller having an internal memory for a digital color graphics imaging system. The controller operates under the direction of a host computer to generate synchronized color data signals for input to a cathode ray tube monitor or other suitable graphical display device. The controller is effective to randomly address its memory at high speed and serially read, but not serially write, the data stored in the memory at TV rates for displaying on the monitor. The particular embodiment of the controller disclosed herein has a universal organization which may be adapted for use in various computer graphics systems. The controller may be operated by software capable of automatic stepping in X and Y directions to provide for transfer of data into the memory using a first word length and for transfer of data out from the memory using a second longer word length, the controller including specific X and Y address registers for computer addressing into the controller's internal memory at those memory locations specified by the computer or at locations which are reached by incrementing or decrementing the X and Y address registers one step in X and/or Y directions or by loading a new absolute address, the controller being capable of determining and changing values of each word to be stored in memory for presentation on the monitor at a specific location based upon a previous value of that same word combined with other input data from the host computer.

Color table animation

Abstract: Even a small amount of animation can greatly enhance graphic communication—particularly when it is desired to show change, movement, or a complex idea or relationship. In raster scan display systems, however, the cost of providing animation has usually been prohibitively high due to the large bandwidths involved in changing a picture rapidly. This paper describes a simple method for providing a limited but very useful real-time interactive animation capability on many existing frame buffer systems. Color table animation relies on changing only the colors of objects and areas present within a single, static picture via the frame buffer's color table RAM. Several variations of this technique are discussed and examples are given of such a capability in use for illustration, educational animation, and television graphics.

An algorithmic approach to controlling search in three-dimensional image data

Abstract: In many three-dimensional imaging applications random shaped objects, reconstructed from serial sections, are isolated to display their overall structure in a single view. This paper presents an algorithm to control an ordered search strategy for locating all contours of random shaped objects intersected by a series of cross-section image planes. Classic search techniques in AI problem solving and software for image processing and computer graphics are combined here to aid program initialization and automate the search process thereafter. Using three-dimensional region growing, this method isolates all spatially connected pixels forming a structure's volume and enters image planes the least number of times to do so. An algorithmic description is given to generalize the process for controlling search in 3-D image data where little core memory is available. Phantom and medical computer tomographic data are used to illustrate the algorithm's performance.

Vector coding of computer graphics material

Abstract: Computer graphics material after raster scanning and digitizing is examined for linear narrow width areas of like light value, typically black or white. Runs of like value on successive scan lines are compared for contiguity and, when found, are compactly coded by coordinates of first and last scan lines defining each area and thickness. Data compaction ratios up to 36 to 1, as compared to the amount of data required to store data for every picture element, can be achieved in real time.

Raster graphics for interactive programming environments

Abstract: Raster-scan display terminals can significantly improve the quality of interaction with conventional computer systems. The design of a graphics package to provide a “window” into the extensive programming environment of interlisp is presented. Two aspects of the package are described: first, the functional view of display output and interactive input facilities as seen by the programmer, and second, the methods used to link the display terminal to the main computer via a packet-switched computer network. Recommendations are presented for designing operating systems and programming languages so as to simplify attaching display terminals.

Special Feature: Interactive Graphics Teleconferencing

Abstract: Interactive graphic displays of layouts or design plans, already in widespread use as design aids, can be even more effective when used in conjunction with teleconferencing.

Stereoscopic computer graphics for simulation and modeling

Abstract: A visually effective stereoscopic CRT display technique has been developed which uses continuous tone computer graphics in combination with electro-optic shutter viewing devices. The technique involves the generation of left and right perspective views of an object model using continuous tone computer graphics. The perspective views constitute stereo pairs and are displayed in an alternating manner on the even and odd field scans of a conventional 2:1 interlace raster scan CRT display. When viewed with electro-optic shutters operated synchronously with the CRT field scan rate, the alternating perspective views are perceived as stereoscopic images with strong binocular depth-of-field sensations. Lightweight stereoscopic viewing glasses have been developed which use lead lanthanum zirconate titanate (PLZT) ceramics as electronically controlled shutter elements. Representative applications of the stereoscopic display technique to dynamic flight simulation and complex molecular modeling are presented. The flight simulation illustrates a landing sequence on an aircraft carrier while the modeling application shows complex three-dimensional structures of double helix DNA and bacterial ferredoxin molecules. The stereoscopic display technique has been shown to be highly effective for adding binocular depth-of-field to computer graphics displays with a resulting enhancement of object model realism.

The Instructional Effectiveness of Three Levels of Graphics Displays for Computer-Assisted Instruction.

Abstract: : To date there is little evidence to support the widespread belief of educators and trainers that the use of visual displays enhances instructional effectiveness. This lack of supporting data is critical when computer-based education systems are considered training delivery vehicles; systems capable of providing sophisticated graphics displays are costly. The purpose of this experiment was to obtain data comparing the instructional effectiveness of three types of graphics displays for computer-assisted instruction (CAI). Three groups of subjects each studied one of three versions of a CAI lesson on the psychophysiology of audition. The text of the lesson was identical for all versions; the type of graphics used in the lesson was different for each group. No control group was used. Graphics were either low level (schematic representations and boxed alphanumerics), medium level (line drawings), or high level (animations plus line drawings). After completing the lesson, all subjects were tested for retention of four knowledge categories addressed in the lesson: acquisition and use of principles, identification of structures, definitions and use of terminology, and memory of specific facts. Results indicated that the type of graphics used during the CAI lesson did not affect lesson completion time or final performance on the retention tests.

Algorithm for Generating a Digital Straight Line on a Triangular Grid

Abstract: An algorithm is presented for generating the optimum straight-line approximation for a plotter constrained to move a unit distance at a time in one of six equi-spaced directions. The algorithm facilitates the drawing of digital straight lines on a triangular grid.

A tutorial on compensation tables

Abstract: The generation of computer-shaded pictures requires that a program calculate intensities for each pixel. These intensities are then viewed on a monitor or transferred to film. It is desirable that ...

Representation and discretization of arbitrary surfaces for finite element shell analysis

Abstract: An interactive computer graphics system has been developed for generating the geometric description of an arbitrary shell surfface. The various difficulties facing the user of sophisticated, doubly-curved shell finite elements and the inefficiency of preprocessing for shell analysis are discussed to explain the benefits of this system. The method is a synthesis of spline theory and algorithms, and an interactive means for man–machine communication. The basic technique employed is a modified lofting method in which cardinal splines. An inversion procedure is incorporated which increases significantly the efficiency of the B-spline approximation process. Static and dynamic graphic displays greatly enhance visualization at any stage of the procedure. Two examples of practical interest are presented in some detail to demonstratge the flexibility and usefulness of this approach. Some natural extensions of this system for interactive mesh generation on the surface are also demonstrated.

Characterizing chemical systems with on-line computers and graphics

Abstract: Incorporating computers and graphics on-line to chemical experiments and processes opens up new opportunities for the study and control of complex systems. Systems having many variables can be characterized even when the variable interactions are nonlinear, and the system cannot a priori be represented by numerical methods and models. That is, large sets of accurate data can be rapidly acquired, then modeling and graphic techniques can be used to obtain partial interpretation plus design of further experimentation. The experimenter can thus comparatively quickly iterate between experimentation and modeling to obtain a final solution. We have designed and characterized a versatile computer-controlled apparatus for chemical research, which incorporates on-line instrumentation and graphics. It can be used to determine the mechanism of enzyme-induced reactions or to optimize analytical methods. The apparatus can also be operated as a pilot plant to design control strategies. On-line graphics were used to display conventional plots used by biochemists and three-dimensional response-surface plots.

An Area Shading Graphics Display System

Abstract: A computer graphics display system for rapidly shading areas on a raster scan screen is described. With the system, the host computer provides the display controller with the parameters of a set of component trapezoids which cover the area to be shaded. The paper gives an algorithm for use in the host to decompose an arbitrary polygon into component trapezoids and it describes a microcomputer based controller to shade the trapezoids.

Design Considerations for Computer-Based Interactive Map Display Systems

Abstract: : A discussion of the key features of an interactive map display system that affect both the usefulness of the system and the design and architecture of its hardware and software. Recent developments in computer graphics offer the possibility of creating interactive map display systems having many of the advantages of traditional paper maps, but significant additional advantages as well. This report presents observations and guidelines for developers of interactive map systems. The techniques and design principles discussed are applicable to command and control systems ranging from support of a field commander through systems tailored to the needs of the National Command Authority.

A terrain and cloud computer image generation model

Abstract: A method is presented that produces a realistic simulation of terrain using source data from the Defense Mapping Agency (DMA). Spatially compact objects are presently modeled with some success at r...