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"Forces for growing hair" doesn't preserve hair length
Closed, ArchivedPublic

Description

System Information
Operating system: Darwin-18.5.0-x86_64-i386-64bit 64 Bits
Graphics card: Intel(R) Iris(TM) Graphics 6100 Intel Inc. 4.1 INTEL-12.8.38

Blender Version
Broken: version: 2.81 (sub 9), branch: master, commit date: 2019-09-09 17:22, hash: rB6be3348505ce
Worked: (optional)

It doesn't work on 2.8 as well

Short description of error

When using "Use for Growing Hair" in "Field Weights" I'd expect that selected forces will be used for modelling hair, but the total hair length will be the same as specified in "Hair Length" field. Instead forces affect hair length as well.

Using forces for modelling hair would be very useful (e.g. to simulate collision with head and avoid buggy Dynamic Hair that requires animation steps) but currently is not very usable because of this issue.

Could Blender make constraint when using forces for growing hair so each grown segment is of equal length? (i.e. make forces affect direction of hair, not their length).

Details

Type
Bug

Event Timeline

Brecht Van Lommel (brecht) closed this task as Archived.
Brecht Van Lommel (brecht) claimed this task.

This kind of feedback is outside the scope of the bug tracker, please use other channels:
https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

This is not feedback, this is bug: hair length was set but it's not grown to given length

The hair length specified is the initial hair length before forces are applied, that's the intended behavior currently and possible improvements to that are outside the scope of the bug tracker.

Would you accept PR that allows to change this behavior? (e.g. "Preserve max length" checkbox)?

The particle system is currently end of life and waiting to be replaced, normally we will not add new features to it anymore.
https://wiki.blender.org/wiki/Modules#Nodes_.26_Physics

If it's a simple change we might accept it, but in general I would not recommend working on that area.