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Maniphest T45531

Parenting object with constraint causes tansform
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Description

System Information
Ubuntu 14, 3xGTX580

Blender Version
2.75a

Short description of error
Parenting object with constraints in some cases causes tansform, even if constraint explicitly does not affect particular transform type (rotation/position) directly.

Exact steps for others to reproduce the error
In attached file parent object with a constraint to the empty.
Object changes position/rotation.

Details

Type
Bug

Event Timeline

Konstantins Visnevskis (kivig) created this task.Jul 22 2015, 11:51 PM
Konstantins Visnevskis (kivig) raised the priority of this task from to Needs Triage by Developer.
Konstantins Visnevskis (kivig) updated the task description. (Show Details)
Konstantins Visnevskis (kivig) added a project: BF Blender.
Konstantins Visnevskis (kivig) set Type to Bug.
Konstantins Visnevskis (kivig) added a subscriber: Konstantins Visnevskis (kivig).
Bastien Montagne (mont29) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Jul 25 2015, 10:47 AM
Bastien Montagne (mont29) added a subscriber: Bastien Montagne (mont29).

Please try again, looks like you missed attaching your .blend file here.

Bastien Montagne (mont29) closed this task as Invalid.Jul 25 2015, 12:15 PM
Bastien Montagne (mont29) claimed this task.

Thanks for the file, but no bug here, setting the constraint is not enough, it does not set the inverse matrix. You have to click on 'Set Inverse' button to do so (and your child object will go back to its original location).

Konstantins Visnevskis (kivig) added a comment.Jul 26 2015, 1:23 AM

There is no set inverse button in the Copy rotation constraint.

Konstantins Visnevskis (kivig) added a comment.Jul 27 2015, 10:27 PM

Maybe I mis-described something. With the present setup in the file (no need to create new constraints), when parented, object changes position, though constraint is not even position related.

Bastien Montagne (mont29) reopened this task as Open.Jul 27 2015, 10:34 PM

OK… See the issue, reopening for now, no time to investigate in coming days though.

Bastien Montagne (mont29) removed Bastien Montagne (mont29) as the assignee of this task.Jul 27 2015, 10:35 PM
Bastien Montagne (mont29) raised the priority of this task from Needs Information from User to Normal.
Gyro Gearloose (pink.vertex) added a subscriber: Gyro Gearloose (pink.vertex).EditedJul 31 2015, 2:39 PM

parent_with_constraint.blend454 KBDownload

Not sure why blender copies constraints to workob.

As a workaround disable the constraints before parenting and enable them afterwards

Sergey Sharybin (sergey) closed this task as Archived.Jul 29 2016, 12:23 PM
Sergey Sharybin (sergey) claimed this task.
Sergey Sharybin (sergey) added a subscriber: Sergey Sharybin (sergey).

Constraints are quite weak in Blender and a subject for major re-code for 2.8. So would rather stop fixing non-a-regressions in this area and switch all energy to a new design.

Mentioned in the TODO list: https://wiki.blender.org/index.php/Dev:Source/Development/Todo/Animation#Constraints

Thanks for the report!