Hair particle system ignoring Density Vertex Group when there are particle edits (from particle editmode) #117372

New Issue

Raza-Zaidi · 2024-01-20T23:08:17+01:00

Raza-Zaidi commented

2024-01-20 23:08:17 +01:00

System Information
Operating system: Windows 10
Graphics card: RTX 3080 Ti

Blender Version
Broken: 3.4.1
Worked: Untested

Not quite sure how it happened. I was creating hair to export to Unreal Engine as a Groom. I was able to export successfully but when I came back, the hair was all over the place instead of where the vertex group is.

I tried to create a new particle system and that successfully assigns its hair to the vertex group.
I tried copying the particle settings from my particle system to the new particle system and that also broke it.

Steps to reproduce from scratch

Open default scene
Create one vgroup and assign some verts to it.
add particle system on cube (switch to hair)
Edit/add new particles
Now assign vgroup to density
If we swap last to steps then it works

I have attached the .blend file along with the ticket.

This is what it looks like:

This is what it should look like:

The hair exported successfully but was broken when I came back into Blender.
I have also attached the allembic file that was exported from Blender containing the properly placed hair, for Unreal.

**System Information** Operating system: Windows 10 Graphics card: RTX 3080 Ti **Blender Version** Broken: 3.4.1 Worked: Untested Not quite sure how it happened. I was creating hair to export to Unreal Engine as a Groom. I was able to export successfully but when I came back, the hair was all over the place instead of where the vertex group is. - I tried to create a new particle system and that successfully assigns its hair to the vertex group. - I tried copying the particle settings from my particle system to the new particle system and that also broke it. **Steps to reproduce from scratch** - Open default scene - Create one vgroup and assign some verts to it. - add particle system on cube (switch to hair) - Edit/add new particles - Now assign vgroup to density If we swap last to steps then it works - - - I have attached the .blend file along with the ticket. This is what it looks like: ![image](/attachments/db647e19-564a-4ef3-8c1d-00628acb2531) This is what it should look like: ![image](/attachments/bf59a2c7-d56f-4d0a-987a-9bc6b2538efb) The hair exported successfully but was broken when I came back into Blender. I have also attached the allembic file that was exported from Blender containing the properly placed hair, for Unreal.

Scout.blend

22 MiB

Scout_Hair.abc

74 KiB

image.png

440 KiB

image.png

440 KiB

image.png

3.1 MiB

Raza-Zaidi added the

labels 2024-01-20 23:08:18 +01:00

Raza-Zaidi commented

2024-01-20 23:25:50 +01:00

Quick Update: I think I may be mistaken regarding when this happened. I also modified the mesh slightly.

Did some cuts with the knife tool here to make the faces smaller. I think I noticed the hair broken after that.

The mesh's origin also seems to have hair on it now

Quick Update: I think I may be mistaken regarding when this happened. I also modified the mesh slightly. ![image](/attachments/f1995950-31ee-469b-9e17-195ccc1e0868) Did some cuts with the knife tool here to make the faces smaller. I think I noticed the hair broken after that. The mesh's origin also seems to have hair on it now ![image](/attachments/2e7d9c93-d4f6-413d-951e-4fca1649b2ce)

image.png

462 KiB

image.png

243 KiB

Pratik Borhade commented

2024-01-22 07:09:38 +01:00

Hi, thanks for the report. Clearing edits done in particle edit mode fixes the problem (hard to guess what actually caused this)
Can you check?

Hi, thanks for the report. Clearing edits done in `particle edit` mode fixes the problem (hard to guess what actually caused this) Can you check?

Pratik Borhade added

Status

Needs Information from User

and removed

Status

Needs Triage

labels 2024-01-22 07:09:49 +01:00

Raza-Zaidi commented

2024-01-22 08:10:12 +01:00

Hi, thanks for the report. Clearing edits done in particle edit mode fixes the problem (hard to guess what actually caused this)
Can you check?

Yes it does clear this up. Though I want to keep the edits. I added some hair manually at precise locations and am trying to find a solution to this rather than redoing because I need to make more hair and im afraid this might happen again to a larger batch with more time invested

> Hi, thanks for the report. Clearing edits done in `particle edit` mode fixes the problem (hard to guess what actually caused this) > Can you check? Yes it does clear this up. Though I want to keep the edits. I added some hair manually at precise locations and am trying to find a solution to this rather than redoing because I need to make more hair and im afraid this might happen again to a larger batch with more time invested

Raza-Zaidi commented

2024-01-24 18:09:53 +01:00

How do I change the status from "Needs Information From User"? I've already provided the information

Pratik Borhade commented

2024-01-25 07:06:37 +01:00

If you clear particle edits -> assign density vgroup -> edit particles, then it would work.

But it seems vgroup assignment is not reflecting in viewport when strands are already edited, confirming

Simple way to repro:

Open default scene
Create one vgroup and assign some verts to it.
add particle system on cube (switch to hair)
Edit/add new particles
Now assign vgroup to density
If we swap last to steps then it works

If you clear particle edits -> assign density vgroup -> edit particles, then it would work. But it seems vgroup assignment is not reflecting in viewport when strands are already edited, confirming Simple way to repro: - Open default scene - Create one vgroup and assign some verts to it. - add particle system on cube (switch to hair) - Edit/add new particles - Now assign vgroup to density If we swap last to steps then it works

Pratik Borhade added

and removed

Needs Information from User

labels 2024-01-25 07:07:00 +01:00

Philipp Oeser changed title from ~~Hair particle system suddenly stopped ignoring Density Vertex Group.~~ to Hair particle system ignoring Density Vertex Group when there are particle edits (from particle editmode)

2024-01-31 09:55:50 +01:00

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Hair particle system ignoring Density Vertex Group when there are particle edits (from particle editmode) #117372