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Parent Inverse is insufficiently explained in documentation
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Description

System Information
Operating system:
OSX 10.13, Win7, Ubuntu

Blender Version
All I know

Description
Something seems wrong with the hierachy (Parent) system in the 3d space.
When transforming a parent, the children transform accordingly. Also their transformation values in the properties don't change. But when I add a new child, it keeps it "global" transformation and now I have two children which are in different coordinate systems. Which one is the right one?
Even with python I get the exact same transformation in my example (picture below).
where does Blender stores the information, that some objects are scaled and others not.
In my opinion this is very intransparent fo the user.

How to reproduce

  • create two cubes (cube1( pos = 0.0, 0.0, 0.0) and cube2( pos = 2.5, 0.0, 0.0))
  • make cube2 child of cube1
  • now scale the parent cube times 3.0
  • create a third cube (pos = 2.5, 0.0, 0.0) and make it a child of cube 1
  • compare pos and scale Values of cube2 and cube3
    • they seem to be the same but aparently the size and location in the viewpoint differs.

maybe give the user the possibility to switch between from parent deformated coordiantes and world coordiantes.

Event Timeline

Brecht Van Lommel (brecht) claimed this task.

As far as I can tell all the described behavior is working as designed. Parenting can be done in different ways.
https://docs.blender.org/manual/en/dev/editors/3dview/object/properties/relations/parents.html

If you want to make suggestions to change the design, then the bug tracker is not the place for that.
https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

I object.

When adding the parent via the relation property in the object properties the parenting behaves like intended.
In any option of the ctrl + P menu, Blender does something strange to the transformation under the hood, which is not accessable to the user.
I have read the whole "Parenting Objects" manual page and I canot find an explanation for this behaviour.

To me, it seems more like a bug which has been there for a long time.

That's not a bug, it's what's called the Parent Inverse Matrix. In python that's called object.matrix_parent_inverse. Alt-P -> Clear Parent Inverse clears it.

Edit: The documentation does seem to be unclear/incorrect regarding Parent Inverse though, so maybe this is a documentation bug.

ok, understood. interesting...
then sorry for the inconvenience.

Alexander Gavrilov (angavrilov) renamed this task from hidden factor of transformation with from parent deformed objects to Parent Inverse is insufficiently explained in documentation.Apr 19 2019, 12:57 PM

maybe I just write a Post in right click select about making this information more prominent