© 1985 by British Computer Society
Pad Structures for the Rainbow Workstation
University of Cambridge, Computer Laboratory, Corn Exchange Street, Cambridge, UK
The Rainbow Workstation is an experimental device built to evaluate a method of supporting windows by dynamically mapping memory to video. The main features of its architecture have been published elsewhere. In this paper a software interface between the workstation and its driving programs is described. The interface provides simple facilities that assist in setting up a virtual terminal system in the workstation and in addition some novel and powerful graphics effects for sophisticated host programs to call upon. The use of lookup table indirections in conjunction with the mapping of memory to video enables some picture manipulations to be achieved very quickly. For example, object silhouettes of any shape can be clipped to one another as quickly as they can be repositioned on the screen. The blending of an anti-aliased image against its background can also be done, as the image moves about, with no time penalty. The basic system design is given in outline, as the background to these techniques, but the method of recomputing the screen is described in more detail.
* University of Cambridge, Computer Laboratory, Corn Exchange Street, Cambridge CB2 3QG
Primary author for correspondence.