Hair blowing up/ exploding

[Ksusha (Ksusha K)]

Hello!

I need some help with hair dynamics. I have an issue with hair colliding with its emitter (character mesh). If the character’s mesh does not have collision physics, everything works fine, but the hair comes through the mesh. If character’s mesh has collision physics, hair blows up / flies around (?).
[1 st picture]

The picture below [2 nd picture] shows siuation when main mesh does not have collision physics. Nice and smooth

To prevent hair from coming through the mesh, I tried adding a «collision» physics to the main mesh. But this resulted in the hair getting «blown». The hair preserves its length and root’s position, so it does not look like a random hair explosion, but rather like something that indicating a problem with collision. But this is only a guess.
[3 rd picture]

I carried out a small experiment: I deleted the collision physics for the main character’s mesh, added a UV-sphere with collision physics, and made my character’s hair collide with that sphere. That worked fine.
[4 th picture]

I tried: I scaled the sphere down so that it fits in the character’s head, and I parented the sphere to the head bone. Hair still blows
[5 th picture]

I tried increasing quality steps and collision quality to 7, but that did not help

I played with inner and outer thicknesses in physics collision, but that did not help

I tried duplicating the main mesh, deleting all particles from it and giving this duplicate a physics «collision» while not having a physics «collision» on the main mesh with hair, but to no avail.

I tried duplicating only the part of the character’s head from which hair particles «grow» from, deleting the particle system for the main mesh, and giving the main mesh «collision», but it did not help (it ended up with both «blown up» hair and messed up hair shape)

I brought the collision distance in the hair particles settings to the minimum (0.001 m)

I tried all of the aforementioned with scale applied to the main mesh

I would like the hair to behave like it does in the second picture, but without falling through the mesh. Could you please tell me how to achieve that? I will be grateful for any help

I am new to Blender and I am using Blender 3.6.0

Link to my file https://cloud.mail.ru/public/zb6w/Kj7mpv9tH

[Matakani]

When you made a copy of the part of the head the hair come from, did you also lift it up? If you leave it in the same location the hair is still immediately colliding with the head.
In your third image the collision distance is 0.001. So lift the scalp up 0.002.

[Ksusha (Ksusha K)]

Thank you for your reply. For the expriment I moved sculp even further than 0.002, but Blender keeps doing the same thing
here is the distance

and here is the result

[goorman (Sergey)]

Hi,

There’s Blender 3.6.1 as far as I know, have you tried that version? Maybe it’s a bug or something.

Download — blender.org

The other thing you could try is to re-create your hairs again. Remove the current one, and make it once again from the scratch.

[goorman (Sergey)]

Seems like I got it working.

1. First of all, turn off the Gravity option in the Scene settings:

2. Then, go to your particles settings, make a duplicate of the original one and turn off the original one as well:

3. Reduce all the way down to 0.000 values such as: Gravity, All, Force and Wind.

4. Turn off the Hair Dynamics option as well

5. Delete the previous baking and make a new one.

You’ll end up with something like this below:

P.S. I have turned off Subdivision modifier from the Realtime mode in order to get a faster animative picture.

P.S.S. You could also get away without disabling the Hair Dynamics, but playing with its settings. Just something like this:

In this case, you’ll end up with the similar result below:

I could’ve attached the .blend file here as well, but it’s way too large, even zipped one is about ~18 mb.

Hope it helps

Cheers,
Sergey

[goorman (Sergey)]

A few more additional details:

If you wouldn’t change anything, but just go to your Collision tab and reduce your Thickness Outer all the way down to 0.001:

Then went on to your Particles tab, delete your previous Baking and bring the next changes into your Hair Dynamics (see screenshot below):

Then bake your animation again, you’ll end up with the next result below:

I think this method would be the best suitable for you

Cheers,
Sergey

[Ksusha (Ksusha K)]

Thank you very much!

[goorman (Sergey)]

You’re welcome!

Glad if it’s helped you.