PRADIS: an advanced programming system for 3-D-display

The development of PRADIS was started in early 1968 as a vehicle to implement and evaluate new schemes of man-machine-interaction, data base organization, and hidden-line detection which were being developed in our laboratory. With time it evolved into a rather elaborate programming system for generation, construction, manipulation, and perspective display of arbitrary three-dimensional objects. All relevant object types such as polyhedrons or groups of polyhedrons with convex or concave structure, objects that are described by analytical expression, as well as the most general case of objects that are bounded by arbitrarily curved surfaces can be handled. Different modes of defining and inputting objects and different-hidden-line suppression algorithms have been individually developed and implemented for these various types. Man-machine-communication has been facilitated by defining a simple command language for the user. The execution of any command can be initiated by pointing to the respective instruction in a command menu. Additionally, a keyboard (or the console typewriter) can be used for specification of parameters or the description of objects by analytical equations. Subroutines for scaling, translation, and rotation are part of the system as well as program modules which enable the user to construct three-dimensional objects by drawing two-dimensional views of them.