Fur
101
Digital hair and fur is one area that has always instilled fear in the hearts of VFX supervisors, because in the past it was so much work to get an even slightly convincing effect, required fur specialists (called “groomers,” somewhat unfortunately. I vividly remember a conversation with an artist working on Harry Potter, who told me with a straight face that his job was to “groom all the children.”)
Whilst large VFX houses do still have grooming departments, creating 3D hair and fur is significantly easier than it used to be. Let’s make some now.
Play with it
Let’s go through the steps to build a controllable hair system in 3D. As always in film, the battle is in reducing the complexity as much as possible to maximise control.
Because of this, when we’re doing a groom, we use guide hairs. Use as few of these as possible, and groom those instead of trying to comb millions of hairs!
From there, you can play with different brushes for more art‑directed control, and using maps to control behaviour. This is where texture and fur overlap, as both can take texture inputs to control colour but also shader attributes, and in the case of fur, behavioural attributes (e.g. a wetness map would be used to make the hair shinier, but also to make the fur stick together more).
Place guides
Click the surface to add one, or use Delete. Everything else in this panel updates live, so jump to Groom or Style whenever you want and come back.
Click the surface to place one.
The first mistake everyone makes is covering their creature with fur and then getting a brush out and grooming it to death. NOPE. Place one guide at a time, and use as few of them as you can get away with.
Groom
Pick a brush, drag on the fur. You move guides, and the children follow.
Once your guide curves are placed, it’s time to get brushing! Digital hairbrushes have more magic than real ones. You can grow, shrink, increase or decrease density with them. Most 3D packages give you lots of options, but the name of the game is pushing your guide curves around until the hair feels naturalistic.
Style nodes
The procedural stack. Clump, then break the clump.
In 3D, these would typically be nodes or attributes that affect whole areas of fur/hair.
Attribute maps
Paint a strip, or drop a pattern. Shift-drag erases.
It’s very common to use texture to help your groom. Typically the skin of your creature will have its own shader and materials, and your groom will have a different set.
Lighting and Shading
Melanin
Hair shaders behave very differently to normal shaders. Instead of colour picking, you choose the amount of melanin (pigment) in the hair. If you have none, the hair will be white. If it’s full, it will be black. Blond and brown are in between.
Redness
The second attribute (here called “redness”) is actually to do with the physical structure of the hair, which also influences its colour in real life, and generally varies according to race, in humans.
Roughness
I’m not going to tell you what roughness means.
Natural variation
In production, you’ll normally have some natural variety in all these attributes, since it’s very rare for hair or fur to be identical in its roughness and pigmentation across the entirety of a person or animal.
Local colour (i.e. no lighting).