Currently Revit, SketchUp, Blender, Cinema4D, Maya and 3ds Max are officially supported. Other packages can be used with Indigo by exporting your model as a .dwg or .obj file and importing it into Blender. Blender is a free rendering package.
You must have Indigo installed and an exporter for a 3d package installed to render with Indigo.
If see an exporter that is currently not supported and would like to create one contact firstname.lastname@example.org. Also, see Indigo Technical Reference for technical documentation on how to create your own.