Is it hard to modify hair in 3D to follow gravity?

[santiago_campanella]

I am considering starting to make 3D renders for my VN, and I have been wondering why for the most part, VNs have hair which doesn't follow human poses, even when the character is upside down (hair is still locked to head and is hanging from down to up). Is it because it's hard or impossible to do hair correctly in existing rendering engines, or just because most devs don't think it matters?

Is there any particular engine/software which can do hair properly in that respect (ie, have some "gravity" direction for the shape, and have individual hairs follow the gravity to some degree)?

 

[Synx]

Most devs use DAZ for their renders and DAZ tools for physic/gravity based modifier is very lackluster compared to other render engines. DAZ provides an easy way for beginners to get decent renders compared to other ender engines, and is designed around that philosophy. It has the tools for more complex stuff like animations with physics, but it's more a side thing than a main part of the kit. It's pretty bad and tiresome to use, so for your average developer it's just not worth using it. Most animations made with DAZ are just pre-made packages people bought/pirated.

For most other render engines it isn't particularly challenging to apply gravity to hair. Just check youtube for tutorials for whatever render program you would use (Blender is the main option used here after DAZ since its free).

 

[woody554]

literally anything is possible in 3d, it just takes increasing amounts of knowledge. some hair is easy to simulate, some won't work (without additional work) because the hair is not connected to anything. ultimately you could learn to make your own hair as you wish, but that's again a step up on the ladder.

shorter answer: of course you can apply gravity to anything, but it might not give you the result you're expecting. gravity is not the hard part.

 

[Guntag]

Even in AAA games, they're lazy with this. Mostly tied or short hair.

 

[qwsaq]

Hair is a very complex feature with a lot of moving parts. To do this hyper-realistically, you're basically talking about simulating not just gravity, but collisions with what amounts to countless strands of fabric. And not just how those strands interact with the character model, but between other strands. Each of those strands would have countless joints and hitboxes which would all have to be calculated while you're trying to render.
Unless you want to put in all the effort to model all of those strands and then wait a week for your RTX 4070 to simulate all of that information for every individual frame, without even being sure if the end result is going to be acceptable and you're not just going to have to restart the simulation, you're gonna cut corners somewhere. The most corner-cutting way is to basically treat the hair like a piece of plastic glued to their head and ignore the problem entirely. Though some level of pliability is necessary if you don't want it to look like a piece of plastic glued to their head.

As Guntag said: even AAA studios cut corners with hair because of how massive a pain in the ass it is to simulate.

 

[woody554]

Unless you want to put in all the effort to model all of those strands and then wait a week for your RTX 4070 to simulate all of that information for every individual frame, without even being sure if the end result is going to be acceptable and you're not just going to have to restart the simulation, you're gonna cut corners somewhere.

we're talking about static renders here so of course it's no problem simulating thousands of individual hairs. but it's not really the good way to do it, instead you model low poly cards of hundreds of hairs each and simulate those which is very easy. and really the polyline hair doesn't look that good to begin with, it's just the lazy way instead of actually modeling the hairstyle you want.

that's why most of daz hairstyles look like they got run over with a lawnmower, because it takes minutes to generate shitty polyline hair with ridiculous amount of unnecessary geometry.