Child bone erraticly flips to the other side of the parent when parent is tracking-to #82463

New Issue

J-W. Versteegh · 2020-11-06T16:04:47+01:00

J-W. Versteegh commented

2020-11-06 16:04:47 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.22

Blender Version
Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: 3e85bb34d0
Worked: none

Short description of error
Child bone erraticly flips to the other side of the parent, when the parent crosses X while tracking to a moving empty.

Exact steps for others to reproduce the error

Load my blend file (with sourcefile Bereken locatie E.py).
Select Bone_F, disable Track-to (Axle_E).
Rotate Bone_F along X; Bone_F2 sticks to Bone_F the way I want it to, it rotates with it, keeping the angle with Bone_F steady.
Now run the code in the text-editor (with Bereken locatie E.py). It calculates the position of empty Axle_E with every frame-change.
Select Bone_F and enable Track-to (Axle_E).
The problem is emminent now: Bone_F2 flips to the side of Y where the head of Bone_F is too.

I want it to retain its fixed rotation-position to Bone_F, so always pointing left in this case (without needing extra constraints of course).

I tried it also both in Blender 2.79 and 2.92.0 Alpha.

As EF.001.blend

Bereken locatie E.py

Thanks in advance,
JWblender.

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.22 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `3e85bb34d0` Worked: none **Short description of error** Child bone erraticly flips to the other side of the parent, when the parent crosses X while tracking to a moving empty. **Exact steps for others to reproduce the error** - Load my blend file (with sourcefile Bereken locatie E.py). - Select Bone_F, disable Track-to (Axle_E). - Rotate Bone_F along X; Bone_F2 sticks to Bone_F the way I want it to, it rotates with it, keeping the angle with Bone_F steady. - Now run the code in the text-editor (with Bereken locatie E.py). It calculates the position of empty Axle_E with every frame-change. - Select Bone_F and enable Track-to (Axle_E). - The problem is emminent now: Bone_F2 flips to the side of Y where the head of Bone_F is too. ``` I want it to retain its fixed rotation-position to Bone_F, so always pointing left in this case (without needing extra constraints of course). ``` - I tried it also both in Blender 2.79 and 2.92.0 Alpha. [As EF.001.blend](https://archive.blender.org/developer/F9218954/As_EF.001.blend) [Bereken locatie E.py](https://archive.blender.org/developer/F9218958/Bereken_locatie_E.py) Thanks in advance, JWblender.

J-W. Versteegh commented

2020-11-06 16:04:47 +01:00

Added subscriber: @JWblender

Richard Antalik commented

2020-11-10 20:46:15 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-11-10 20:46:15 +01:00

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

Richard Antalik commented

2020-11-10 20:46:15 +01:00

Thanks for report, but your code is quite complex. Can you simplify it as much as possible and tell us what exactly does not work as expected?

We don't provide technical support here. For support and technical discussions please use one of the community websites: https://www.blender.org/community/

Thanks for report, but your code is quite complex. Can you simplify it as much as possible and tell us what exactly does not work as expected? We don't provide technical support here. For support and technical discussions please use one of the community websites: https://www.blender.org/community/

J-W. Versteegh commented

2020-11-21 17:37:14 +01:00

Thanks for reacting.
The code calculates the crossing point(s) of two circles. They are two distances point E must adhere to.
It works as expected and places object E (named axle_E) at the right location.
This location is where the head of bone Bone_F should be. Is working fine.
I want bone Bone_F2 to be exactly 90 degrees onto bone Bone_F.
When I rotate bone Bone_F with Track To disabled, bone Bone_F2 follows Bone_F correctly as I want.
But when I enable Track To for Bone_F, is seems to flip constantly.

Kind regards,
Jan-Willem Versteegh

Thanks for reacting. The code calculates the crossing point(s) of two circles. They are two distances point E must adhere to. It works as expected and places object E (named axle_E) at the right location. This location is where the head of bone Bone_F should be. Is working fine. I want bone Bone_F2 to be exactly 90 degrees onto bone Bone_F. When I rotate bone Bone_F with Track To disabled, bone Bone_F2 follows Bone_F correctly as I want. But when I enable Track To for Bone_F, is seems to flip constantly. Kind regards, Jan-Willem Versteegh

Richard Antalik commented

2020-11-23 16:21:49 +01:00

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

Richard Antalik closed this issue

2020-11-23 16:21:49 +01:00

Richard Antalik commented

2020-11-23 16:21:49 +01:00

Thanks for info, so the script doesn't play any role here - you need 2 bones and Axle_E to demonstrate this.
I had to google if this is known issue and apparently it is caused by Track To constraint. I guess this would be similar issue as #56176

If you replace Track To constraint by Damped Track, it works well.

Thanks for info, so the script doesn't play any role here - you need 2 bones and Axle_E to demonstrate this. I had to google if this is known issue and apparently it is caused by Track To constraint. I guess this would be similar issue as #56176 If you replace Track To constraint by Damped Track, it works well.

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Child bone erraticly flips to the other side of the parent when parent is tracking-to #82463