Hi keith - I tested your model and could not reproduce the anomalies you show using Cinema4D. Most likely you are not getting the proper vertex normals over into Carrara and it is instead having to try and generate the smoothing from the polygon data rather than the shading coming from the original NURBS surface normals which is what you want to have happen.

I guess the first question is what file format are you using for the transfer, is it possible you are using .3ds format? If so then that's the problem - .3ds is a kind of antique file format that does not support vertex normal data in it. Instead try using .obj format and make sure any option for importing normals from the .obj file is enabled.

I tested your file above carSubbed.3dm, and I exported an .obj file using these settings (I cranked the slider all the way to the right and put in a distance value of 0.25 to just force some more divisions on some slightly long and skinny polygons to get more regularly diced up sizes which can be helpful:




Then importing that into Cinema4D and rendering it I could not find any evidence whatsoever of those anomalies:




So I think it's likely that you are not getting the good vertex normal shading data coming over into Carrara. Make sure you are using .obj format for the transfer, check any import options to see if importing normals is turned off, and another thing is to make sure you are doing a full render and not just worrying about anomalies you see in a real-time display versus a full render.

- Michael