The good old and worthy lisp based geometry translator from Autocad to radiance. Still works fine with all versions of Autocad on all platforms, as long as you don't use any of the new fancy entity types like acis solids etc.
Radout is a very close reimplementation of torad, but it is written in ADS-C and therefore a lot faster. Note that the free version ignores ACIS solids, which are only supported in our commercial products.
A command line utility to convert geomety data from Autocad DXF files to the radiance scene file format. Dxf2rad understands all versions of DXF files and translates everything it finds, except for data that requires third party modules like the ACIS solid modelling entities. Free for all platforms that are supported by Rayfront.