Particle Hair Weight does not work (it's either 0 or 1) #84580

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Ethical Vegan · 2021-01-11T00:06:23+01:00

Ethical Vegan commented

2021-01-11 00:06:23 +01:00

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

Blender Version
Broken: 2.91

Short description of error

A weight of 1 works as expected, the key does not move with physics. But anything below a weight of 1 is the same as 0. So a weight of 0.99 is the same as 0.

Exact steps for others to reproduce the error

The hair on the right: gradient (root has weight 1, tip has weight 0)
The hair in the middle: root has weight 1, all the other keys have weight 0.001)
The hair on the left: root has weight 1, all the other keys have weight 0.99)

As you can see each hair behaves exactly the same way with hair dynamics, no matter what the weights of the keys are (anything from 0.001 to 0.99), as long as the weight is not 1.

It's a big problem for me because I want to have physics only at the end of the hair, and I need to make a gradient that goes from 1 to 0. But now, since weights don't work, this would look like the hair is made out of metal, then suddenly becomes soft at the end.

Edit: Sample project
untitled.blend
When opening the project, the cube is already selected and you are at frame 9 in the timeline to see that each of the 3 hair behaves the same. Go to Ctrl-Tab -> Particle Edit too see the weights, which I set the same way as described above.

**System Information** Operating system: Windows 10 Graphics card: Geforce 1070 **Blender Version** Broken: 2.91 **Short description of error** ![BLENDER BUG.png](https://archive.blender.org/developer/F9558870/BLENDER_BUG.png) A weight of 1 works as expected, the key does not move with physics. But anything below a weight of 1 is the same as 0. So a weight of 0.99 is the same as 0. **Exact steps for others to reproduce the error** ![BLENDER BUG.png](https://archive.blender.org/developer/F9558870/BLENDER_BUG.png) - The hair on the right: gradient (root has weight 1, tip has weight 0) - The hair in the middle: root has weight 1, all the other keys have weight 0.001) - The hair on the left: root has weight 1, all the other keys have weight 0.99) ![BLENDER BUG 2.png](https://archive.blender.org/developer/F9558880/BLENDER_BUG_2.png) ![BLENDER BUG 3.png](https://archive.blender.org/developer/F9558882/BLENDER_BUG_3.png) As you can see each hair behaves exactly the same way with hair dynamics, no matter what the weights of the keys are (anything from 0.001 to 0.99), as long as the weight is not 1. It's a big problem for me because I want to have physics only at the end of the hair, and I need to make a gradient that goes from 1 to 0. But now, since weights don't work, this would look like the hair is made out of metal, then suddenly becomes soft at the end. **Edit: Sample project** [untitled.blend](https://archive.blender.org/developer/F9559797/untitled.blend) When opening the project, the cube is already selected and you are at frame 9 in the timeline to see that each of the 3 hair behaves the same. Go to Ctrl-Tab -> Particle Edit too see the weights, which I set the same way as described above.

Ethical Vegan commented

2021-01-11 00:06:23 +01:00

Added subscriber: @EthicalVegan

Falk David commented

2021-01-11 09:04:19 +01:00

Added subscriber: @filedescriptor

Falk David commented

2021-01-11 09:04:19 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Falk David commented

2021-01-11 09:04:19 +01:00

Could you provide the test file you used in the screenshots so I can try to reproduce the problem? You can edit the task and just drag the file onto the textbox to upload it.

Ethical Vegan commented

2021-01-11 13:52:15 +01:00

I edited and added the sample project with a small description

Falk David commented

2021-01-11 15:11:18 +01:00

Thank you. From looking at the file I can see that "Pin Goal Strength" under "Hair dynamics" was set to 0.0. On hairs "the weight defines the soft body Goal" (https://docs.blender.org/manual/en/dev/physics/particles/mode.html#brush under Weight). If the strength is set to e.g. 1.0 you get this:

Which I think is what you wanted. If there is no issue then I will close the report.

Thank you. From looking at the file I can see that "Pin Goal Strength" under "Hair dynamics" was set to 0.0. On hairs "the weight defines the soft body Goal" (https://docs.blender.org/manual/en/dev/physics/particles/mode.html#brush under Weight). If the strength is set to e.g. 1.0 you get this: ![hairs.png](https://archive.blender.org/developer/F9559852/hairs.png) Which I think is what you wanted. If there is no issue then I will close the report.

Falk David commented

2021-01-11 15:12:10 +01:00

Changed status from 'Needs User Info' to: 'Archived'

Falk David closed this issue

2021-01-11 15:12:10 +01:00

Ethical Vegan commented

2021-01-11 15:38:15 +01:00

Thank you! In the doc you sent it is written "... This value is scaled by the Strength Min to Max range of soft body goals…"
Nothing mentions any connection with Pin Goal Strength. Should the doc be modified to say "This value is scaled by Pin Goal Strength" instead?
Right now I don't see how anyone could figure this out on their own.

Thank you! In the doc you sent it is written "... This value is scaled by the Strength Min to Max range of soft body goals…" Nothing mentions any connection with Pin Goal Strength. Should the doc be modified to say "This value is scaled by Pin Goal Strength" instead? Right now I don't see how anyone could figure this out on their own.

Falk David commented

2021-01-11 15:41:49 +01:00

It says "soft body goals" because this (presumably) also applies to e.g. cloth, hair, and all other soft bodies.

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Particle Hair Weight does not work (it's either 0 or 1) #84580