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Hair instability with collision
Closed, ResolvedPublic


System Information
Operating system: Windows 10
Graphics card: Geforce GTX 1070

Blender Version
Broken: 82c3fdd559b32d88881883b99cf441935401cf05

Short description of error
If dynamic hair comes in contact with collision object, the hair "explodes."

Exact steps for others to reproduce the error

  1. Open attached file.
  2. Bake hair simulation of cube.
  3. Hair explodes as soon as it contacts suzanne.
  • Reproduced this with several emitter / collider meshes, particle settings etc.

Event Timeline

Sebastian Parborg (zeddb) lowered the priority of this task from 90 to 50.EditedJan 24 2019, 11:54 AM

Hair collisions never really worked in the first place. See this example (the left one is the current blender hair physics):

IIRC there are plans to rewrite the particle/hair system. Hopefully problems like these will be solved then.

@Brecht Van Lommel (brecht) should we archive this or leave it as confirmed?

Brecht Van Lommel (brecht) lowered the priority of this task from 50 to Low.

This system has no maintainer currently, so marked as low priority without assignee.

@Sebastian Jansson (sebastian) Parborg (zeddb) Any updates on the particle/hair system rewrite? Are there any ways I can keep track of its progress?


Going over hair issues atm (to clear the tracker -- but also to have some input on what the next system has to take care of)

Note that this (explosion) only happens if the Hair Dynamics > Quality Steps are above 1.
There is a (newer) report open just for that, see T65038: Hair Dynamics: Hair quality steps more than 1 results in increased collision reaction [like a multiplier]
I afaics, this was not the case in 2.79.
Not too familiar with the hair system, but maybe @Juan Gea (juang3d) can comment if he thinks this is a bug (I think it is)? (have a look at T65038)

I will check T65038.

In any case Hair collission is flawed because it tries to do tri-tri intersections instead of edge-tri intersection, I spoke about this with @Luca Rood (LucaRood) about this and he gave me clues on how to fix this, I am not experienced with this at all, but I¡ll try to solve it as soon as I can.

But maybe the T65038 is a different problem because hair quality steps more than 1 should result in better result, not in explosion