What software did you use for the fur?
Dave: With a relatively short production schedule, and the fur being a key focus of the werewolves, developing our own properietary fur program was not an option. We went with the best alternative which was Joe Alter's Shave and a Haircut. We needed a dependable product that could create realistic fur and be fast enough to make quick client iterations. S&H quickly proved it's worth; giving us the ability to quickly groom, animate and render great looking fur in very little time.
Were there any major technical hurdles to overcome with the fur?
Dave: The major obstacles were creating large amounts of wet, matted fur while trying to keep the render times reasonable. To control the wet looking hair, we used multiple, concentrated specular maps on the fur and exaggerted the wet look once more in the compositing phase. To give compositors additional specular control, a separate specular fur pass was rendered. For instance, since rendering fur specular per light would consume too much render time, we would render a single pass with scattered R, G, and B hues. This pass could then be keyed out and adjust more in comp, giving us more spec information to work with. This also allowed more variation to be added to the specular component as a final touch.
Rendering the fur was the next challenge. Since the fur was so heavy and took so long to render with Mental Ray, we decided to use Maya's software renderer. This still gave us great looking fur but we came across slight gaps left between the fur and skin renders due to the skin being displaced by Mental Ray. We solved this problem by rendering a separate patch of fur to fill in the gap. The result was flawless.
Using IBL to light the fur was not an option so it was up to the lighter to create the look. Using the plate as reference for light color and direction we were able to acheive better, dramatic lighting. Since compositing also played a large role in the final look of the fur, the lighter would get the look as close as possible and the compositor would tweak the rest instead of relying on re-renders. In order to give the compositor freedom to adjust the lighting of the fur, the lighter would render the fur with each light having a red, green, or blue value. The compositor could then adjust each light's intensity or color in Shake which made lighting iterations more streamlined.
For werewolf transformation shots, the lighter had to generate greyscale intensity maps, which controlled the fur growth. To create these intensity maps, we used a proprietary sculpt deformer called "capsules". These capsules were then placed around the areas of the werewolf where we wanted fur to grow from. If the capsule touched or encompassed the surface, it would return a value of white, while the areas not being affected would be a black value. These maps were then baked out as a sequence and plugged into a shader that used the values to create growing fur. To eliminate the look of scaling fur, random jitter and noise was added to give the growth some extra life.