Hair child particles changing seed on each frame of anim

Is there some setting so child hair particles arent changing on each frame?? Im grooming on alembic cache of my character (model doesnt change vertex ids or anything). Its obvious that happens on just child hair particles because the main doesnt change postions (seed).

Would be cool if someone give me any clue what could cause this trouble…

Im using the latest b3d ver 2.8 with Cycles render. (Not Eevee)

Here is video for showcase of this problem:



By default they are not changing on each frame. Maybe its hair dynamics, it’s hard to tell without the blend file.

thx for your reply!

Well there is not dynamics enabled at all…maybe the alembic animation doesnt work with hairs.

But it was my intention to groom on abc file and then switch for animated abc later (which obviously works…in terms of hair groom which doesnt break when switching source alembic file)

Its a nice and elegant way for transfering grooms across scenes. Not sure what kind of workflow guys at Blender Institute uses because there is no info in the blender manual about this at all…

Thanks anyway!

Hi! Are you using virtual parents? I found that option causes this problem

thx for your input!

After some test I can clearly say its the "Child hair particles issues when using “Interpolated” mode, when using child hair particles with “Simple” method IT WORKS. I will try to find that Virtual Parent thingy and play with it…

…I ve been doing some more tests to find out whats the problem and realized that it also happens when rendering with Eevee :frowning: (good thing is that its not Cycles render issue but sort of blender / user fail:)

After some more tests…Im pretty sure its Alembic format related bug or something.

Doing quick fur setup on rigged character works flawless using child hair particles and “Interpolated” mode.

So the question is, is there some Alembic export/import setting I m not aware of? Or is it just bug within hair system when groomed on alembic cached model…

Any ideas?

Thanks. L.

P.S. @Strangerman nope, I dont use Virtual Parent settings at all…thx anyway!

Ok, I think Im done with this…its a bug in Hair particles groomed on alembic cache.

I ve done more tests and this is my conclusion from it.

If you are interested here is test scene

…just change mode on Child hair particles from Interpolated to Simple and it start to work normally.

The scene is ready to render in eevee so u can quickly have anim seeing the errors. Feel free to play with it or any settings, maybe you come up with some workaround/solution.

I quess I should report it to the devs…