Wrong orientation for hair particles in Object or Group render mode #42397

New Issue

Quentin Wenger · 2014-10-26T00:15:23+02:00

Quentin Wenger commented

2014-10-26 00:15:23 +02:00

System Information
Any

Blender Version
Blender 2.72b - but it has been there for many releases, I f.E. found the same behaviour in Blender 2.66 and did not search further.

Short description of error
When creating a particle system in hair mode and "Object" render option, duplis show out with wrong orientation.
It is like if there was following transformation applied:

x --> z
y --> -y
z --> x

Thus, applying the inverse transformation (which is actually the same) would solve the problem. But it turns out that it is actually x and z vectors (in the code: vec and nor) that should simply be swapped.

N.B.: results are the same in Group render mode, all instances get this wrong orientation.

Exact steps for others to reproduce the error
Open Blender
Edit the cube to have it dyssymetric (or add a Monkey instead, this is just for visualisation)
Add a plane, scale it in edit mode (just to have it easier to work on)
Add a particle system to it, choose the render option Object and set the Cube as the dupli object
Toggle the Rotation option to get the "cube" (or Monkey) in the same orientation as the original instance.

Now, switch the particle system to Hair mode
Again toggle the Rotation option in the render section
Both orientations (w/ or w/o Rotation) give bad orientation compared to those in Emitter mode.

Diff
Here is the .diff showing this swap:
blender_bke_hairpartori.diff

**System Information** Any **Blender Version** Blender 2.72b - but it has been there for many releases, I f.E. found the same behaviour in Blender 2.66 and did not search further. **Short description of error** When creating a particle system in hair mode and "Object" render option, duplis show out with wrong orientation. It is like if there was following transformation applied: ``` x --> z y --> -y z --> x ``` Thus, applying the inverse transformation (which is actually the same) would solve the problem. But it turns out that it is actually x and z vectors (in the code: vec and nor) that should simply be swapped. N.B.: results are the same in Group render mode, all instances get this wrong orientation. **Exact steps for others to reproduce the error** Open Blender Edit the cube to have it dyssymetric (or add a Monkey instead, this is just for visualisation) Add a plane, scale it in edit mode (just to have it easier to work on) Add a particle system to it, choose the render option Object and set the Cube as the dupli object Toggle the Rotation option to get the "cube" (or Monkey) in the same orientation as the original instance. Now, switch the particle system to Hair mode Again toggle the Rotation option in the render section Both orientations (w/ or w/o Rotation) give bad orientation compared to those in Emitter mode. **Diff** Here is the .diff showing this swap: [blender_bke_hairpartori.diff](https://archive.blender.org/developer/F119689/blender_bke_hairpartori.diff)

Quentin Wenger commented

2014-10-26 00:15:24 +02:00

Changed status to: 'Open'

Quentin Wenger commented

2014-10-26 00:15:24 +02:00

Added subscriber: @QuentinWenger

Quentin Wenger commented

2014-10-26 00:19:39 +02:00

Oops, small error in the .diff, here is a new version:

blender_bke_hairpartori.diff

(By the way: I cannot edit my own tasks !?)

Oops, small error in the .diff, here is a new version: [blender_bke_hairpartori.diff](https://archive.blender.org/developer/F119691/blender_bke_hairpartori.diff) (By the way: I cannot edit my own tasks !?) ![locked_task.png](https://archive.blender.org/developer/F119692/locked_task.png)

Lukas Tönne was assigned by Bastien Montagne

2014-10-26 09:31:39 +01:00

Bastien Montagne commented

2014-10-26 09:31:39 +01:00

Added subscriber: @mont29

Bastien Montagne commented

2014-10-26 09:31:39 +01:00

(only devs can edit tasks themselves, iirc).

Lukas, this one sounds for you! ;)

(only devs can edit tasks themselves, iirc). Lukas, this one sounds for you! ;)

Quentin Wenger commented

2014-10-26 10:02:53 +01:00

Well, that's kind of strange... Am I not the owner of this task, as its author?

Well, that's kind of strange... Am I not the owner of this task, as its author? ![access_denied.png](https://archive.blender.org/developer/F119721/access_denied.png)

Kévin Dietrich commented

2014-10-26 15:05:12 +01:00

Added subscriber: @kevindietrich

Kévin Dietrich commented

2014-10-26 15:05:12 +01:00

Only the owner of a task can edit it, and by owner it is meant the one to whom the task is assigned (or the one who claims it), in this ticket it would Lukas. The author is just the one who creates it. This is some kind of Phabricator security thing. Changing this behavior is being talked upstream [here ]] and https:*secure.phabricator.com/D10012 . Then, everyone listed [ https://developer.blender.org/project/view/1/ | here can edit tasks without being the owner, not necessarily developers.

Only the owner of a task can edit it, and by owner it is meant the one to whom the task is assigned (or the one who claims it), in this ticket it would Lukas. The author is just the one who creates it. This is some kind of Phabricator security thing. Changing this behavior is being talked upstream [here ]] and [[ https:*secure.phabricator.com/D10012 | here ]]. Then, everyone listed [[ https://developer.blender.org/project/view/1/ | here ](https:*secure.phabricator.com/T5681) can edit tasks without being the owner, not necessarily developers.

Quentin Wenger commented

2014-10-26 16:54:16 +01:00

Ok, thanks for clarifying! ;-)

Lukas Tönne commented

2014-10-29 13:42:17 +01:00

Please make a test file, otherwise i can't say if this is a bug or not.

Generally i think that hair and object instancing should not be combined and are incompatible features (big problem with particles), but that's just my personal opinion.

Please make a test file, otherwise i can't say if this is a bug or not. Generally i think that hair and object instancing should not be combined and are incompatible features (big problem with particles), but that's just my personal opinion.

Quentin Wenger commented

2014-10-29 18:35:23 +01:00

Ok, there you go:

272b_test_suzanne_particlesorientation.blend

In that file, there are Suzanne at the center and two planes on the left and the right; all three objects have the default orientations.

Each planes has a particle system, that is configured the same way, except:

the particle system of the left plane is of type emitter, the one on the right is of type hair;
duplis size is not the same (but it doesn't matter, it is just to have a uniform aspect).

What you can see is that particles on the right plane (hair mode) have an orientation that doesn't correspond to anything (you can find the relations in my first post). Even if you uncheck options "Rotation" in the dupli context, you don't get equal result; and obviously, emitter particles are correct, the others wrong.

Here is an example of videotutorial where the author complains about it... and he is not the only one.
https://www.youtube.com/watch?v=TJ_OcBh7F5I#t=1974

Ok, there you go: [272b_test_suzanne_particlesorientation.blend](https://archive.blender.org/developer/F120191/272b_test_suzanne_particlesorientation.blend) In that file, there are Suzanne at the center and two planes on the left and the right; all three objects have the default orientations. Each planes has a particle system, that is configured the same way, except: 1) the particle system of the left plane is of type emitter, the one on the right is of type hair; 2) duplis size is not the same (but it doesn't matter, it is just to have a uniform aspect). What you can see is that particles on the right plane (hair mode) have an orientation that doesn't correspond to anything (you can find the relations in my first post). Even if you uncheck options "Rotation" in the dupli context, you don't get equal result; and obviously, emitter particles are correct, the others wrong. Here is an example of videotutorial where the author complains about it... and he is not the only one. https://www.youtube.com/watch?v=TJ_OcBh7F5I#t=1974

Lukas Tönne commented

2014-12-03 09:57:45 +01:00

Changed status from 'Open' to: 'Archived'

Lukas Tönne closed this issue

2014-12-03 09:57:45 +01:00

Lukas Tönne commented

2014-12-03 09:57:45 +01:00

Particle rotation is utterly broken, no way this can be fixed properly without causing more issues. Has to be considered a todo, in the meantime i suggest not to try and match hair and emitter stuff, it's just not compatible anyway.

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Wrong orientation for hair particles in Object or Group render mode #42397