[Bf-funboard] Reasoning behind child - parent coordinates

Knapp magick.crow at gmail.com
Fri Apr 17 18:59:15 CEST 2015

On Fri, Apr 17, 2015 at 6:00 PM, Gatis Kurzemnieks <
gatis.kurzemnieks at gmail.com> wrote:

> Hello.
> 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,
> Gatis
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Just a guess, but could this be yet another strangeness of the old
dependency graph that the devs are working hard to repair/rewrite??

Douglas E Knapp

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