Particle Hair Dynamics #73370

New Issue

Graham Cripps · 2020-01-24T19:00:41+01:00

Graham Cripps commented

2020-01-24 19:00:41 +01:00

System Information
Operating system: Linux-4.15.0-54-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: Radeon RX 580 Series (POLARIS10, DRM 3.33.0, 4.15.0-54-generic, LLVM 8.0.0) X.Org 4.5 (Core Profile) Mesa 19.0.2

Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2020-01-24 11:47, hash: 18343c230d
Worked: (2.79)

Short description of error
If you have a hair particle system with Hair Dynamics activated, it stops working when you change the object from Shade Flat to Shade Smooth.

Exact steps for others to reproduce the error
Add any mesh object . With the object selected add a particle system, change the particle system to Hair and click the tick box for Hair Dynamics. Hit the space-bar to run animation (leave the animation running). Now (still with the sphere selected) Rt mouse click and select 'Shade Smooth' when the animation starts from the beginning the hair particles become ridged. Rt mouse click and select 'Shade Flat' and the Dynamics are back.

[Based on the default startup or an attached .blend file (as simple as possible)]

**System Information** Operating system: Linux-4.15.0-54-generic-x86_64-with-debian-buster-sid 64 Bits Graphics card: Radeon RX 580 Series (POLARIS10, DRM 3.33.0, 4.15.0-54-generic, LLVM 8.0.0) X.Org 4.5 (Core Profile) Mesa 19.0.2 **Blender Version** Broken: version: 2.82 (sub 6), branch: master, commit date: 2020-01-24 11:47, hash: `18343c230d` Worked: (2.79) **Short description of error** If you have a hair particle system with Hair Dynamics activated, it stops working when you change the object from Shade Flat to Shade Smooth. **Exact steps for others to reproduce the error** Add any mesh object . With the object selected add a particle system, change the particle system to Hair and click the tick box for Hair Dynamics. Hit the space-bar to run animation (leave the animation running). Now (still with the sphere selected) Rt mouse click and select 'Shade Smooth' when the animation starts from the beginning the hair particles become ridged. Rt mouse click and select 'Shade Flat' and the Dynamics are back. [Based on the default startup or an attached .blend file (as simple as possible)]

Graham Cripps commented

2020-01-24 19:00:41 +01:00

Added subscriber: @craigievar

Graham Cripps commented

2020-01-24 19:08:10 +01:00

The bug is easily reproduced from the start-up file. For this reason I have not uploaded a blender file.

Richard Antalik commented

2020-01-27 14:04:08 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-01-27 14:04:08 +01:00

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

Richard Antalik commented

2020-01-27 14:04:08 +01:00

In #73370#857876, @craigievar wrote:
The bug is easily reproduced from the start-up file. For this reason I have not uploaded a blender file.

I can not reproduce this, so I would like a .blend file.

> In #73370#857876, @craigievar wrote: > The bug is easily reproduced from the start-up file. For this reason I have not uploaded a blender file. I can not reproduce this, so I would like a .blend file.

Graham Cripps commented

2020-01-27 14:46:28 +01:00

ParticleHairBug.blend

Hi Richard

I have discovered you do need to have 1000 (default) or more strands for the dynamics to stop working. The attached Blender file has two identical UVspheres both with particle hair systems with the dynamics active. The sphere set to shade smooth, the hair is rigid. Whereas the sphere set to shade flat, the hair flops down as it should.

I hope this helps

Graham

[ParticleHairBug.blend](https://archive.blender.org/developer/F8304945/ParticleHairBug.blend) Hi Richard I have discovered you do need to have 1000 (default) or more strands for the dynamics to stop working. The attached Blender file has two identical UVspheres both with particle hair systems with the dynamics active. The sphere set to shade smooth, the hair is rigid. Whereas the sphere set to shade flat, the hair flops down as it should. I hope this helps Graham

Richard Antalik commented

2020-01-27 15:17:30 +01:00

I opened the file, hit spacebar to play and hair fell down on both spheres. Up to frame 31 broken state is in cache.
Hm not sure what's happening here, as soon as I do anything that clears the cache, file works as expected.

Perhaps try fresh daily build, update drivers, factory startup... But I don't see any recent relevant fixes.

I opened the file, hit spacebar to play and hair fell down on both spheres. Up to frame 31 broken state is in cache. Hm not sure what's happening here, as soon as I do anything that clears the cache, file works as expected. Perhaps try fresh daily build, update drivers, factory startup... But I don't see any recent relevant fixes.

Graham Cripps commented

2020-01-27 16:53:23 +01:00

Hi Richard

Sorry you are having problems with this. I have just downloaded the latest (today 27 Jan) 2.82 Beta and 2.83 Alpha and in both cases on the sphere set to shade smooth the hair remains ridged - no hair dynamics. BTW I run Linux but also have Windows10 on a separate boot, I have just tried on there with the latest 2.81a - same result, no hair dynamics on the shade smooth sphere. I will try this on a different computer all together - it may take a bit of time, and let you know.

Graham

Hi Richard Sorry you are having problems with this. I have just downloaded the latest (today 27 Jan) 2.82 Beta and 2.83 Alpha and in both cases on the sphere set to shade smooth the hair remains ridged - no hair dynamics. BTW I run Linux but also have Windows10 on a separate boot, I have just tried on there with the latest 2.81a - same result, no hair dynamics on the shade smooth sphere. I will try this on a different computer all together - it may take a bit of time, and let you know. Graham

Graham Cripps commented

2020-01-27 20:38:17 +01:00

Hi Richard

I have now had the chance to try the Blend file on another machine and using the latest version of Blender the Hair Dynamics run correctly! The hairs do not go ridged when 'Shade Smooth) is selected.

However I do have this problem on the computer I use for work, both in Windows10 and Linux Mint 19.2

If it helps my computer has an ASRock AB350 Gaming-ITX/ac mainboard, AMD Ryzen 5 2600X processor and a Radeon RX 580 6GB graphics card.

I am sorry that, just like my second machine you cannot reproduce this.

Graham

Hi Richard I have now had the chance to try the Blend file on another machine and using the latest version of Blender the Hair Dynamics run correctly! The hairs do not go ridged when 'Shade Smooth) is selected. However I do have this problem on the computer I use for work, both in Windows10 and Linux Mint 19.2 If it helps my computer has an ASRock AB350 Gaming-ITX/ac mainboard, AMD Ryzen 5 2600X processor and a Radeon RX 580 6GB graphics card. I am sorry that, just like my second machine you cannot reproduce this. Graham

Richard Antalik commented

2020-01-27 20:46:18 +01:00

I have RX 550 and I am on windows, so we have quite similar setup.

Can you try to update GPU drivers on windows and see if that resolves the issue?

I have RX 550 and I am on windows, so we have quite similar setup. Can you try to update GPU drivers on windows and see if that resolves the issue?

Graham Cripps commented

2020-02-01 11:03:09 +01:00

Hi Richard

Thanks for your advice - sadly it did not help. However it appears i am not alone I found this:

https://blender.stackexchange.com/questions/148516/hair-dynamics-doesnt-work

I have also found a different problem, also with dynamic hair, this time I have tested it with the latest alpha and beta on two different machines with two different versions of Linux and Windows10. I can reproduce the problem on all!

Should I file this as a separate bug?

Anyway here is how to reproduce it.

From the start screen, add a particle system to the cube. Change to hair and set the number of strands to 250, switch on Hair Dynamics and change from Object Mode to Particle edit. Comb the particles so some at the top cut though the top face of the cube. Change back to Object Mode and click the animation play button. Some of the particles that cut thought the cube 'dance' around and just will not be still. This and the fact that the strands can cut through objects is not how hair is in reality.

I have also added a Blend file.

DynamicHairBug.blend

Should I file this as a separate bug or is it OK as a comment here?

Hi Richard Thanks for your advice - sadly it did not help. However it appears i am not alone I found this: https://blender.stackexchange.com/questions/148516/hair-dynamics-doesnt-work I have also found a different problem, also with dynamic hair, this time I have tested it with the latest alpha and beta on two different machines with two different versions of Linux and Windows10. I can reproduce the problem on all! Should I file this as a separate bug? Anyway here is how to reproduce it. From the start screen, add a particle system to the cube. Change to hair and set the number of strands to 250, switch on Hair Dynamics and change from Object Mode to Particle edit. Comb the particles so some at the top cut though the top face of the cube. Change back to Object Mode and click the animation play button. Some of the particles that cut thought the cube 'dance' around and just will not be still. This and the fact that the strands can cut through objects is not how hair is in reality. I have also added a Blend file. [DynamicHairBug.blend](https://archive.blender.org/developer/F8315655/DynamicHairBug.blend) Should I file this as a separate bug or is it OK as a comment here?

Richard Antalik commented

2020-02-03 06:22:27 +01:00

Changed status from 'Needs User Info' to: 'Needs Developer To Reproduce'

Richard Antalik commented

2020-02-03 06:22:27 +01:00

@craigievar please make new report for another bug, but please do some search to find out if it's already reported.

Philipp Oeser commented

2020-05-12 15:52:00 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-05-12 15:52:00 +02:00

This looks like a duplicate of #68681 (Hair Dynamics: simulation doesn't work depending on smooth/flat shaded surfaces (and nvidia gpus?)).
Will merge these reports, lets continue discussion there...
(feel free though to comment again if it turns out to be a separate issue from #68681)

This looks like a duplicate of #68681 (Hair Dynamics: simulation doesn't work depending on smooth/flat shaded surfaces (and nvidia gpus?)). Will merge these reports, lets continue discussion there... (feel free though to comment again if it turns out to be a separate issue from #68681)

Philipp Oeser commented

2020-05-12 15:52:09 +02:00

Closed as duplicate of #68681

Philipp Oeser closed this issue

2020-05-12 15:52:09 +02:00

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Particle Hair Dynamics #73370