Most of the software on this page is rather old. The programs have been developed and tested with up to Autocad 2000. The lisp files may work with newer versions as well, but we make no promises.Generate auxiliary construction lines on the plane and in space. A similar concept to xlines and rays, just much more complete and useful as you can create lines in relative position to any straight edge in your drawing. Available for several platforms and releases.
Not really related to 3d-modelling or lighting simulation, but anyway: A relatively simple utility to import HPGL type 1 text format plot files back into autocad.
Draw cylinders (circles with thickness) at arbitrary locations in space. You specify a sequence of points, and this simple program places the cylinders automatically, in any UCS.