Hi ! Thanks for your answer !
Yes we can generate better looking images by changing the light’s and material’s parameters. You can find an example below.
The reason we presented those in the post is because we obtained those with equivalent light and material setup as the ones we obtained with the other methods. And as we think we had to correct the physical interpretation of those parameters in VTK’s shader (Phong’s model, normal estimation), it made sense to us to compare them. And in the interpolation method, the column on the right corresponds to the corrected version of VTK’s existing shader.
Your question about the hybrid row is also very relevant. Actually, this method makes a slightly different physical interpretation of some parameters, and a consequence of it is that with equivalent light and material setup, it looks darker.
Thanks a lot for your feedback !