The MATHEMATICA import does not support the sphere primitive.
Face colors seem to be converted to edge colors only.
RGBColor[] with a fourth transarency argument cause an exception.
It would be nice to have transparency though.
btw. in some rare cases I had the situation that soft and sunflow backends threw exceptions for lineWidth /tubeRadius giving back an java.lang.Integer.
Somehow this seems to come from the MATHEMATICA import.
best
Tim