Erik, software doesn't change behavior randomly. I know that some times it might seem like that but it isn't. 

If you have good rendering with other objects and you new model doesn't render correctly then you have to look at the geometry. You can also restart LuxRender with the debug option active and see if it reports inconsistent normals in the log. If it does then you do have vertex normals that point to the wrong direction.

Cheers.

Paolo

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