I’ve been hacking on a Mitsuba plugin for Rhino 5 and have some preliminary results to share.
Disclaimer: This is an early experimental integration plugin—if you don’t like to edit Mitsuba XML files by hand, it probably won’t be useful to you. The plugin currently only exports geometry and does not support editing materials. I am still waiting for McNeel to provide the necessary API hooks to be able to implement full material support.
On the other hand, the geometry export works quite smoothly even for large geometry with instances and all sorts of crazy shape types. It exports directly to Mitsuba’s native .serialized format, hence the export+open in Mitsuba operation is reasonably fast.
To install it, download Mitsuba.rhp and move it into your Rhinoceros 5.0 Beta/Plug-ins folder. This file then needs to be registered in the Settings using the Install button on the Plug-ins panel (see the first screenshot below). Now, restart Rhino. After the restart, there will be a new Mitsuba panel in the settings (second screenshot below). Select this panel and configure the path to where Mitsuba is installed.
Once this is done, exporting the geometry and opening it in the renderer is as simple as entering Mitsuba on the command prompt. Below, you can see a simple clay realtime preview of an object with sun & sky illumination.
Many thanks go to Nathan Coatney, who provided some guidance in the form of an early version of his Python-based LuxRender exporter.