I'm looking for suggestions for 3D design software which support designing multi-material parts.
I will be printing on a multi-extruder machine based on RepRap firmware. The printer will handle the files when given a proper g-code file. Slic3r will produce a proper g-code file given the right input. STL seems to be single-material, so I am looking for something like AMF files, or any alternative.
My question is, what is available for 3D design software which will produce a geometry file which slic3r (or some other slicing software) will properly process? I'm not asking for opinions on which software is best.
I believe this is my first question in any StackExchange forum, so if I have trespassed on community standards, it was not my intention.