Father of the RepRap and nearly all things DIY 3D printing has managed to bypass the tyranny of the triangle to 3D print directly from OpenSCAD's CSG representation without using an STL file in the workflow.

What does this mean?

Printing directly from CSG is much more robust than using the flakey (literally) STL file format.  A CSG file can be wrong - we can all make mistakes - but, unlike STL, it always represents an unambiguous solid.
It should also be faster (5%)........  Finally, it should allow us easily to do fancy things like filling solids with scalar and vector fields representing build parameters, so you can have an object that is flexible (and/or green) at one end and rigid (and/or blue) at the other.

Visit the RepRap Wiki for instructions on how to use this process on your RepRap.

Perhaps this will actually pave the way to better communicate multiple materials to Objet 3D printers which currently require multiple STL files to create multiple material parts?  

Thank you Adrian