I am having a bug i think. I am trying to render perforated metal with the surface finish tab set to circular hole mesh. I am getting the inverse results. instead of holes in the cylinder i get a bunch or circular patches. i tried the custom hole mesh and selected the SW suuplied image. same result. I then took the image into photoshop and inverted the image like shown. Now it works and creates perforated metal. the problem is if i go back to tweak the hole size it reverts back to a bunch of patches even though the image being used is correct. Once i edit the material it goes back to correct. Bug?