Well, someone released a new hair plugin for Unity.

It uses a populated strand system, like some approaches in Blender and ZBrush.

This "combing and cutting" approach seems like it should produce good hair, but I've never seen good hair using it.

So let's talk 3D hair.

This approach is commonly called a "particle" approach, because the strands are often created using the particle subsystem of the 3D modeling software.

The "particles" emit from the scalp, and you shape their flow.

Normally use use a few anchor particles, then bulk them up.

So you might have, say, 100 anchor particles. You comb them and trim them and adjust them.

At the end, they bulk up by becoming hundreds of thousand of threads.

If you look at The Incredibles, they use this technique.

... Can't find a decent doc about it, though.

Rendering strands like that is way too intensive for a game engine, so normally game hair is NOT made using this approach.

Instead, the hair is made of wide, flat meshes, usually called something like "hair cards". A "hair card" has a texture containing thick, luxurious hair.

Most game hair is made with this approach, often along with "base shapes" that fill in underneath so there's no gaps in the hair cards where you can see scalp.

There is a temptation to simply turn particle strands into these hair cards.

Why not? The particles flow the right way, what's wrong with that idea?

Well, the truth is that hair is very, very hard to do using this kind of brush-and-simulate approach, even using proper fill.

If you've ever tried it, you've probably found your hair lacks body, seems simplistic, and hair motion such as animation bones or shapekeys make it look even worse!

Your strands keep dipping under the scalp or into the neck, it's a mess.

That's because you're not a hair pro.

These problems are made much, much worse when you convert the strands into hair cards instead of thousands of fill strands.

I don't know if anyone could make that look good.

So, how do you create game hair?

... You manually place the hair cards.

All of them.

Here's an example by DannyMac. Technically he's not using "hair cards" because he's not using textures or transparency, but the shapes are the same.

Notice how he places each strand.

Brushing hair strands using a particle system to do this would be incredibly challenging.

Moreover, there's a ton of "cheats" here that you couldn't easily do with particle hair.

It's not "easy", but you don't have to be a pro to create hair that doesn't suck with this approach

If you are aiming for gameready hair, I strongly recommend this approach instead of a particle approach. It's not as hard as it might seem, especially if you are working from a real life hairstyle with reference photos.