Hair physics issues

So, apparently hair physics is the weakest point of blender. Hair wont collide with objects properly except in miracle cases. Hair wont collide with itself. Hair kinda can move in dynamic fashion but hair sim volume settings will make you to bang your head to wall. Whats the point having and updating the solver with volume algorithms if its not finished? And even if you decide to do hair in other software and then import hair curves to blender - Bang! you cant render those unless converting to geometry which kills the render, the hair shader and ability to use any texture.

Is there any proper workflow for blender dynamic hair? Or we just supposed to use it in still frame renders and 1970s static hairstyles?

I have not done a lot of hair work in Blender, but I thought I would give it a try. The Volume based system is too slow for me to use, but there are a few things you can do to improve the mesh based collision experience.
Construct your scalp on a duplicate mesh of the Body. Set the body to be a standard physics collider. Add the particle system to the scalp copy. On the scalp copy, delete everything but the faces you are using for hair emission. With all the faces selected, extrude them out just a tiny bit. This gives the collision system a little bit of breathing room so hairs don’t start off initially in a collision state.

I think hairs starting off in a collision state contributes to some of the problems.

In this GIF, I set the Quality to 14 steps and the hair segments to 24. Try to keep your guide count low, it defaults to 1000, which is way too many. I have 72 in this GIF. Set your child hair viewport display to 100%, the default of 10%, so you get a good idea of what the final is going to look like in the render.

The system could be improved upon, but it does seem usable.
blender%20hair

Here is a mohawk hair style.
blender%20hair

A little bit longer hair style.
blender%20hair

Here is another one, with longer hair. In this one, I have placed a Wind Force Field in the scene to purposely blow the hair back from the face. I also set gravity to 75%, instead of 100%.
blender%20hair

2 Likes

Thanx Atom, and sorry for delayed reply.

There are some very good tips! Scaling the model 20 times kinda solved simulation issue, but another one arised. Seems like you have some experience in hairsim in blender. Did you ever had some hair strands just freeze and not simulating? i cant seem find the cause of the issue. Seems they are shortest ones, but changing their length doesn’t solve the issue.

Seems i fixed the issue. Problem was in point not evenly distributed in strands. Fixing it was different adventure. Basically i converted particle to mesh, used loop tools space function and then used hairnet (5.1) to convert curves to hair.