david3der happy to see you achieved what you needed. Due to shadows, the RN viewport display only touches Rhino on a "minimal surface" to make the viewing experience as swift as possible, thus shadow implementation would be extremely hard. Cycles have to have at least a triangle mesh to render it and cast shadows, besides that, it would have to be a part of the Rhino document, this would cause terrible performance and huge filesize and most probably would crash each time on autosave action due to its size as a real rhino object.
