I have imported a model as obj. from rhino to blender. When i use the Cycles render, some faces are black no matter which material i choose. I have already tried to flip the normals but that didnt work.
I also tried to delete a face when in edit mode and replace it with an extruded edge but that doesnt fix the prblem either. I can only delete the faces and replace them with planes in obj mode.
Here are some pictures of the problem.
Also in material preview mode some models appear with a gradient on them.
