Sketchy Illustrations for Presenting the Design of Interactive CSG

Illustrating in a sketchy manner is essential to communicate visual ideas and can be used to present and reconsider drafts and concepts in product design. This paper introduces a real-time illustration technique that sketches the design and spatial assembly of CSG models. The illustration technique generates a graphical decomposition of the CSG model into disjunctive layers to extract 1) the perceptually important edges that outline the model´s outer and inner features and 2) the surface shading of the outer and inner faces. Then, the technique applies uncertainty to these layers to simulate a sketchy effect. Finally, the technique composes the sketched layers in depth-sorted order while ensuring a correct depth behavior in the frame buffer. Because the sketchy illustrations are frame-to-frame coherent, the technique can be used as a tool for interactive presentation and reconsideration of the design and spatial assembly of CSG models