Creating a tin foil material initially seems like a relatively simple task - just apply a foil texture map and render off. Well, yes, but only if the object is far enough away and is not affected by key lights. The problem is that the scanned / photographed image of the metal has reflections and lighting baked into it so any additional ones that we drop in will not look correct. Additionally we cannot use it as a bump map due to the bump shading it generates. So we will have to create our own shader. The shader in question is constructed using Displacement mapping generated with nested Noise maps to create large and small pitted detail for the uneven surface, with an additional Cellular map as a bump map to create the finer cracks and seams. As this is a shiny metallic surface, we need a large Anisotropic highlight and reflections that reflect the environment - an Anisotropic shader within a Raytrace material will do the job nicely.
As we are making heavy use of material displacement, the material will take longer to render than a simple bump map effect due to the geometry being refined and displaced at render time. However if you have 3ds max 7 (in which the scene included on the CD was created) you can produce an extra pass and use version 7’s new Normal Mapping to create shading to simulate the high displacement detail, resulting in a comparable effect with a fraction of render time (bearing in mind that, again, this is a shading effect on the non-displaced low polygon geometry). With displacement mapping, the more work it has to do the longer it takes to render so use it sparingly on lower polygon objects and resort to other shading methods such as Normal Mapping for more distant objects.
||Although this is lit using HDRI, the end result is effective no matter what lighting solution is used.
||As illustrated, the material tree is not difficult to set up. We have used a Raytrace shader to simulate metal as it gives us more control over our effect.
Try reducing the amount of displacement for tighter foil (less render time) and more for looser foil (longer render time)
World magazine, Issue 62, March 2005.
Draper, March 2005. Reproduction without permission