[Bf-funboard] Reasoning behind child - parent coordinates

Gatis Kurzemnieks gatis.kurzemnieks at gmail.com
Fri Apr 17 18:00:36 CEST 2015

I am wondering what is the logic behind Blenders weird coordinate
calculations when doing parenting operations. What I mean is that child
objects local coordinates are not real local in relation to parent, but
there is the hidden "origin" transformation "matrix_parent_inverse" which
is not represented in UI in any way.
Simple example : Create two objects at 0,0,0. Move one object somewhere and
then take the first object (still at 0,0,0) and parent it to moved object.
You would expect that child objects coords would now be offset relative
from parents, but no - they are still 0,0,0. I mean come on - when childs
local coords are 0,0,0 it should be in the origin of it's parent, right!?

There is a command "Make Parent without Inverse" that parents without the
hidden offset, but it destroys the real offset - putting child in the
center of parent and this is bad. There is also a command called Clear
Origin, that does something similar (but not exactly and not always - and
it is not clear to me what and why. It takes Alt O, Alt G, Alt O again to
clear origin and coords completely in some situations).

I can't see any benefit, reason or logic behind this. This makes things
confusing and conflicts with the way other 3d apps work. And I can't find a
simple solution (besides writing my own python script which I did), to get
normal parenting behavior.

best wishes,

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