Inadequacy of hair lenght in particle edit and bugs of rendering #46112

New Issue

Janis Grinvalds · 2015-09-14T19:04:51+02:00

Janis Grinvalds commented

2015-09-14 19:04:51 +02:00

My project stopped again because of some problems to edit and render hair. I am not new in hair particles and mostly made grass, stones distributions by using systems. But now I am working on 3d portrait and responsiveness of hair are important in order to make good result.
So problems are following:

Particle edit is ignoring length of hair defined by weight of vertex. Switching "Keep, Lengths" does not help.
Imagine that working with hair must be with taking account length which may be shorter, but it's very ineffective.
Children are longer then parents. So if my particle defined by vertex group is 0, then children are longer and appear unwanted where I don't expect them. It's impossible to make them shorter as there's no parameter for absolute length of children, just relative.
I could not mimic that in file example, but in my project file Cycles renders my hair shorter then in view-port, also render mode. Looks that cycles somehow took in account correct children length, but again: it's impossible to control and edit those hair in normal way. And main problem that view-port render mode becomes irrelevant for my hair system, I should again and again make renders to check ir my hair are proper size.

Try swith on/of chidren.
Switch on/of vertex groups.
Go in and out particle edit mode.

Example file: http://www.megafileupload.com/dwWl/hair_problem_lenght.blend

Suggestion for additions: option to apply vertex groups as particle edit.

My project stopped again because of some problems to edit and render hair. I am not new in hair particles and mostly made grass, stones distributions by using systems. But now I am working on 3d portrait and responsiveness of hair are important in order to make good result. So problems are following: 1. Particle edit is ignoring length of hair defined by weight of vertex. Switching "Keep, Lengths" does not help. Imagine that working with hair must be with taking account length which may be shorter, but it's very ineffective. 2. Children are longer then parents. So if my particle defined by vertex group is 0, then children are longer and appear unwanted where I don't expect them. It's impossible to make them shorter as there's no parameter for absolute length of children, just relative. 3. I could not mimic that in file example, but in my project file Cycles renders my hair shorter then in view-port, also render mode. Looks that cycles somehow took in account correct children length, but again: it's impossible to control and edit those hair in normal way. And main problem that view-port render mode becomes irrelevant for my hair system, I should again and again make renders to check ir my hair are proper size. Try swith on/of chidren. Switch on/of vertex groups. Go in and out particle edit mode. Example file: http://www.megafileupload.com/dwWl/hair_problem_lenght.blend Suggestion for additions: option to apply vertex groups as particle edit.

Janis Grinvalds commented

2015-09-14 19:04:51 +02:00

Changed status to: 'Open'

Janis Grinvalds commented

2015-09-14 19:04:51 +02:00

Added subscriber: @JanisGrinvalds

Janis Grinvalds commented

2015-09-14 19:06:08 +02:00

And try to comb hair and see how result differs when You go out of particle edit mode.

Janis Grinvalds commented

2015-09-14 19:11:52 +02:00

Addition to ticket:

After applying scale of emitter, hair changes length proportionally. So if something was sized down and applied, then hairs become larger in global scale.
Maybe blender could check if mesh is emitter object and offers to user apply scale together with hair particle parameters.

Addition to ticket: After applying scale of emitter, hair changes length proportionally. So if something was sized down and applied, then hairs become larger in global scale. Maybe blender could check if mesh is emitter object and offers to user apply scale together with hair particle parameters.

Aaron Carlisle commented

2015-09-14 21:14:32 +02:00

Added subscriber: @Blendify

ronan ducluzeau commented

2015-09-18 12:27:50 +02:00

Added subscriber: @zeauro

ronan ducluzeau commented

2015-09-18 12:27:50 +02:00

Particles workflow is quite old, have a lot of limitations.

Since 2.5 refactor, weight groups cannot be used as a starting point.
It was thought as is :
User is setting particle length of parents in particle edit.
Then, user adjusts relative length of children with weight groups or textures.
There is an option to see children in particle edit.

Particles code is not flexible enough to be corrected without breaking other aspects of particles.
A refactor of particles is needed with a better workflow allowing back and forth between weight painting and particle edit.
But no dev is available to do it before 2.8.

Your report looks like suggestions for this kind of refactor. But it is not valid as a bugreport.

You should respect guidelines and prove that something that was working in a previous release is actually broken.
If it is really the case.
You should precise your OS, computer spec.
Upload .blend file directly in bugtracker by a drag and drop.

Particles workflow is quite old, have a lot of limitations. Since 2.5 refactor, weight groups cannot be used as a starting point. It was thought as is : User is setting particle length of parents in particle edit. Then, user adjusts relative length of children with weight groups or textures. There is an option to see children in particle edit. Particles code is not flexible enough to be corrected without breaking other aspects of particles. A refactor of particles is needed with a better workflow allowing back and forth between weight painting and particle edit. But no dev is available to do it before 2.8. Your report looks like suggestions for this kind of refactor. But it is not valid as a bugreport. You should respect guidelines and prove that something that was working in a previous release is actually broken. If it is really the case. You should precise your OS, computer spec. Upload .blend file directly in bugtracker by a drag and drop.

ronan ducluzeau commented

2015-09-18 13:17:57 +02:00

ubuntu 14.04 64 bits Nvidia Titan Black

I can confirm that since Gooseberry changes.

Hair children length can not be set to zero by a vertex group like it was the case in 2.73.

children_length.blend
Attached .blend file does not look the same if it opened in 2.73 or in 2.74, 2.75, current master.

ubuntu 14.04 64 bits Nvidia Titan Black I can confirm that since Gooseberry changes. Hair children length can not be set to zero by a vertex group like it was the case in 2.73. ![2.73_2.74_children.jpg](https://archive.blender.org/developer/F234173/2.73_2.74_children.jpg) [children_length.blend](https://archive.blender.org/developer/F234175/children_length.blend) Attached .blend file does not look the same if it opened in 2.73 or in 2.74, 2.75, current master.

Sergey Sharybin commented

2015-09-24 10:39:45 +02:00

Added subscribers: @LukasTonne, @Sergey

Sergey Sharybin commented

2015-09-24 10:39:45 +02:00

While there could be some changes caused by Gooseberry project, i don't really see reason why cycles will render hair differently from the viewport. That's something to be looked into.

@LukasTonne, do you have any ideas here?

While there could be some changes caused by Gooseberry project, i don't really see reason why cycles will render hair differently from the viewport. That's something to be looked into. @LukasTonne, do you have any ideas here?

ronan ducluzeau commented

2015-09-24 11:06:08 +02:00

Here, cycles does not render shorter than in viewport.
Without a blend file that shows it, I think that can be a simple impression due to hair tip that can not be draw in viewport as thin as in render.

Here, cycles does not render shorter than in viewport. Without a blend file that shows it, I think that can be a simple impression due to hair tip that can not be draw in viewport as thin as in render.

Sergey Sharybin commented

2015-09-24 11:09:46 +02:00

@zeauro, i've been testing render with original file and could have see the problem. But now the file is indeed gone..

@JanisGrinvalds, please attach simple .blend file with the issue you're having here to the tracker so it's not getting lost again.

@zeauro, i've been testing render with original file and could have see the problem. But now the file is indeed gone.. @JanisGrinvalds, please attach simple .blend file with the issue you're having here to the tracker so it's not getting lost again.

Janis Grinvalds commented

2015-09-24 11:31:38 +02:00

hair_problem_lenght.blend

[hair_problem_lenght.blend](https://archive.blender.org/developer/F238517/hair_problem_lenght.blend)

Sergey Sharybin commented

2015-09-24 11:41:36 +02:00

With the attached file i can see difference between viewport render and viewport opengl only after doing final (F12) rendering. it could be caused bu difference in view/render settings in the particle system..

ronan ducluzeau commented

2015-09-24 13:41:48 +02:00

I confirm that I see same wrong refresh of viewport render after an F12 render. Tweaking a little bit a particle setting forces refresh of viewport render.

Don Howard commented

2015-09-26 16:16:48 +02:00

Added subscriber: @throwcode

Don Howard commented

2015-09-26 16:16:48 +02:00

Hi I'm seeing the same bug as reported by Janis Grinvalds...

I'm using Window 10 pro, 64 bit, Intel i7, 12 GB Ram, Blender 2.76. This bug also occurred in Blender's prior release 2.75a. In both cases while using Cycles renderer.

Description:
The issue involves the Particle System, Vertex Groups panel, Length section. When editing a Hair system that uses the Vertex Group Length section to vary the length of the hair using Weight Painting, Blender fails to properly represent the length of the Hair particles in the Particle Editor.

The bug is very easy to reproduce.

In Blender you will note that in the 3D View the hair is appropriately sized. However when you switch the Object Interaction Mode from Object to Particle Edit the Hair is a uniform length, at the longest setting. This makes it difficult to comb and cut!

Thanks.

TC

Hi I'm seeing the same bug as reported by Janis Grinvalds... I'm using Window 10 pro, 64 bit, Intel i7, 12 GB Ram, Blender 2.76. This bug also occurred in Blender's prior release 2.75a. In both cases while using Cycles renderer. Description: The issue involves the Particle System, Vertex Groups panel, Length section. When editing a Hair system that uses the Vertex Group Length section to vary the length of the hair using Weight Painting, Blender fails to properly represent the length of the Hair particles in the Particle Editor. The bug is very easy to reproduce. In Blender you will note that in the 3D View the hair is appropriately sized. However when you switch the Object Interaction Mode from Object to Particle Edit the Hair is a uniform length, at the longest setting. This makes it difficult to comb and cut! Thanks. TC

Aaron Carlisle commented

2015-09-29 14:25:25 +02:00

@Sergey could this be related to what I reported in #46312

Bastien Montagne commented

2015-10-08 10:23:11 +02:00

Added subscriber: @mont29

Sergey Sharybin commented

2016-02-02 16:09:20 +01:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2016-02-02 16:09:20 +01:00

Sergey Sharybin self-assigned this 2016-02-02 16:09:20 +01:00

Sergey Sharybin commented

2016-02-02 16:09:20 +01:00

Current state of particles is real hard for further fixes, especially when there were intentional changes in other parts of particle system which could cause regression in other configuration. Would consider all such report a TODO for until new particle system is laid down. Thanks for the report anyway.

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Inadequacy of hair lenght in particle edit and bugs of rendering #46112