[Bf-funboard] contraints - a problem.

Ton Roosendaal bf-funboard@blender.org
Wed, 9 Jul 2003 20:33:58 +0200


This is really hard to understand...

> regarding
> the replacement of current parenting with "ADD
> Loc/Rot/Size" constraints.

I don't know who proposed this, or gave a defition of how it works?

Anyhoo, there's something different going we've overlooked a bit... and  
that's that APART from constraints, also the execution order of  
transformations matter.

This is what 'hierarchy' does, it moves one object into the coordinate  
space of another. That's it. Apart from constraining actions.

But, in theory it could be possible to implement a "loc rot size"  
constraint with settings that exactly mimic what Parenting does. Just a  
load of buttons extra to define "pre mul" or "post mul" transformations.

Still thinking it over though... :-)


On Wednesday, Jul 9, 2003, at 12:44 Europe/Amsterdam, Gwyn Perry wrote:

> hi everyone,
> all of this contraint discussion is very interesting,
> almost exactly what i thought the system should be
> when NaN first introduced it.
> however, one small issue has occurred to me regarding
> the replacement of current parenting with "ADD
> Loc/Rot/Size" constraints. unfortunately, i don't have
> FTP access at the moment and can't post diagrams, so
> you'll have bear with me while i try to explain.
> using current parenting system:
> OBJ_A at xyz 0,0,0 is the parent of OBJ_B at xyz
> -2,0,0
> OBJ_A is rotated 90` around Z, placing OBJ_B at 0,2,0.
> so, both objects are rotated 90`, and OBJ_B has moved
> two units +X and +Y. OBJ_A has not moved. all objects
> are, in effect, components of one grand object.
> using proposed "ADD Loc/Rot/Size" constraints:
> exactly the same situation, however, as OBJ_A has not
> moved, OBJ_B has no location to add, therefore doesn't
> move either. Without the linked relationship of
> parenting, the constraints would not perform the same
> job. an add rotation constraint would have a similar
> effect to the "Rotation/Scaling around individual
> object centers" button, except as a constraint, not an
> interaction option.
> In light of this, I would like to propose a complete
> "parent" constraint. This would be in addition to the
> individual "ADD" constraints (which i think are an
> excellent idea)
> later
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Ton Roosendaal  Blender Foundation ton@blender.org