David R. Warn

Lighting controls for synthetic images

The traditional point source light used for synthetic image generation provides no adjustments other than position, and this severely limits the effects that can be achieved. It can be difficult to highlight particular features of an object. This paper describes new lighting controls and techniques which can be used to optimize the lighting for synthetic images. These controls are based in part on observations of the lights used in the studio of a professional photographer. Controls include a light direction to aim a light at a particular area of an object, light concentration to simulate spotlights or floodlights, and flaps or cones to restrict the path of a light. Another control relates to the color of the light source and its effect on the perceived color of specular highlights. An object color can be blended with a color for the highlights to simulate different materials, paints, or lighting conditions. This can be accomplished dynamically while the image is displayed, using the video lookup table to approximate the specular color shift

A Straightforward Model for Computer Performance Prediction

Both simulation and analytic models of computer systems can be very useful for predicting the performance of proposed new systems or proposed changes to exmting systems. Unfortunately, many potential users of models are reluctant to use them because of the complemty of many such models and the difficulty of relating the model to the real system This tutorial paper leads the reader through the development and use of an easily understood analytic model. This is then placed m context with a class of similar analytic models. In spite of the simplicity of these models they have proved useful and quite accurate in predicting performance (utilization, throughput, and response) using only the most basic system data as input These parameters can either be estimates or measurements from a running system. The model equations and assumptions are defined, and a detailed case s tudy is presented as an example of their use

Human factors aspects of a modern data base system

Abstract The focus of this work is to develop tools and procedures so that non-computer specialists can more effectively manage and use data. The results of several research projects over a number of years have given a spectrum of approaches to make data systems easier to use. In our work, the relational model of data was simplified so that novice users could easily understand their data relationships. An algebraic relational command language was developed to bring the power of relational data manipulation to non-programmers. This research was followed by development of an extended command system that allows users to name and describe their data in English words rather than in cryptic abbreviated forms. In parallel with this, a menu interface to a relational system was developed. The degree of completeness of these approaches, the overall effectiveness in actual operation, some data collected from users, and the ease of learning have been analyzed and are reported.

Relational data base support for interactive graphics

A relational data base management system has proven to be an extremely valuable tool for implementing AUTOCOLOR, an interactive graphics application system. AUTOCOLOR generates realistic color synthetic images on a raster display which will permit designers to aesthetically evaluate automotive body shapes even before a clay model is built. Both exterior body surfaces and functional parts constructed with the GMSOLID solid modeling system can be displayed. Color coded scalar values such as stress, pressure, or curvature can also be displayed on the surface of an object. AUTOCOLOR is completely interactive, using menus and screen selection to define parameters and options, select a viewing orientation, or mix a color. The geometry, view, lighting, and image generation information for displaying an object are all stored in tables which can be accessed directly by programs or interactively using data base commands. The tabular organization has proven to be very efficient from the programming point of view. It offers the advantages of array referencing without the overhead of following a linked list or hierarchical structure. The availability of data base functions provides a powerful tool for the manipulation of application data structures. For example, sorting the edge table to generate a different view of an object can be done by a a single command. Data base commands can also perform utility functions like generating the mirror image of a part without writing special purpose programs. Files containing all tables for an object can be saved which makes it possible to create subsequent images very quickly without regenerating previously derived information. The use of a general purpose data base manager reduces the programming effort to implement a system, provides great flexibility, and can be accomplished without loss of execution efficiency. The data base manager supports many of the functions that would have to be provided anyway. These include: space management, creation of data, building a data structure, and location of specific data items.