Interactive rendering of CSG models

We describe a CSG rendering algorithm that requires no evaluation of the CSG tree beyond normalization and pruning. It renders directly from the normalized CSG tree and primitives described (To the graphics sq;stem) by their facetted boundaries. It behaves correctly in the presence of user defined, ''near'' and ''far'' clipping planes. It has been implemented on standard graphics workstations using Iris GL(1) and OpenGL(2) graphics libraries. Modestly sized models can be evaluated and rendered at interactive (less than a second pet frame) speeds. We have combined the algorithm with an existing B-rep based modeller to provide interactive rendering of incremental updates to large models.