M. Muuss, ``Understanding the Preparation and Analysis of Solid Models'', in ``Techniques for Computer Graphics'', ed: Rogers & Earnshaw, Springer Verlag, New York, pages 109-172.
Also in ``The Ballistic Research Laboratory CAD Package Release 4.0 Manuals, Volume V, Analyst's Manual'' Page V5S08A05.
For a discussion of the rt lighting model see:
M. Muuss and P. Dykstra, ``The RT Lighting Model''. in Proceedings of the BRL-CAD Symposium '88, held at the Ballistic Research Laboratory, Aberdeen Proving Ground, Maryland, June 28, 1988.
Also in ``The Ballistic Research Laboratory CAD Package Release 4.0 Manuals, Volume V, Analyst's Manual'' Page V5S10A03.