Hi Keith - yes I do indeed think that the particular problems you were indicating are due to limits in the rendering software that you're using.

The specific problem is that it's easy to get glitches exactly like you show if a particular piece of data called "vertex normals" is not loaded from the polygon mesh file and used to shade the object.

The 2 renderers that you are using (Carrara and Blender) happen to be about the only 2 ones that have this problem. In the past Carrara did not have this problem but apparently they've changed stuff in it in more recent versions that has introduced this problem and made it problematic to use for rendering CAD data. I seem to remember that very recently this may have been solved in Blender but I'm not completely sure about that.

I'd recommend saving your model as an .obj file out from MoI using the option for "Output: Quads & Triangles" and then loading it into SimLab composer and see if that gives you a better looking smooth shading. You can get a trial version of Simlab composer here:
http://www.simlab-soft.com/3d-products/simlab-composer-trial.aspx

Also if you want smoother looking results, moving the slider a little bit to the right to increase the number of polygons created can also help with that, like Chipp shows above.

But the key thing to get a good looking render without shading glitches is to make sure that the vertex normals smoothing information in the .obj file is being loaded and used by the renderer - apparently Carrara is not doing that anymore and so that will lead to shading glitches exactly like the ones that you have been showing that you want to avoid.

- Michael