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View Full Version : Theoretical application of Spline Control parenting behaviour? /joints vs nulls



jeric_synergy
06-26-2014, 10:46 AM
Watching and pondering RebelHill's Spline control video, in which he describes how a parented item in the spline-control-nodes chain behaves.

Basically, it appears ( #awayFromLW ) that only the 'lowest' level item of the chain (I'd have to verify this), the items with no children, contribute to the Spline creation. The 'childfree', if you will.

OK, that's probably a VERY good decision by the coders. Because as RH demonstrates you can use the parent to position a spline control node, although the parent itself is outside the spline.

But, as a practical matter, what situations would benefit from this feature?

I can think of various cool LOOKING things, but nothing just plainly practical. For instance, with this feature making a "jump rope" animated spline should be easy:
SPLINE-OBJECT

1
2

3
4

In a straight line on the Z axis. Now, 2 doesn't contribute to the spline, but its child 3 does. If you rotate 2, and offset 3 on the X or Y axis, the spline will develop the typical jump rope shape and motion.

So, that's pretty cool, I just can't think of a USE for it. :(

If there were a way to use Spline Control for deformation rather than motion (or Instancing (or Flocking?)), this would be swell.

+++
BTW, there IS a plugin that converts Modeler Curves to the SPline Control setup in Layout. One of the niftier aspects of this (Python?) script is that it uses JOINTS instead of Nulls as the spline control objects. Joints have at least 2 advantages as Spline Control items:
Their UI representation differs from nulls and are easier to see.
They are automatically children of a given object, so you can skip the parenting step.


So, even if you are constructing a Spline Control by hand, you might consider using ADD JOINT instead of Nulls.

jeric_synergy
06-26-2014, 12:26 PM
Starting at 15:26, RH starts describing the special case of Bones controlled by Spline Control, which BINGO! gives us "deformations controlled by Spline Control" that I was whinging about above:

https://www.youtube.com/watch?v=gCVneRb141I

This immediately gives us easy(-ish) animation of things like jump ropes for the scenario I referred to, but also any hoses and whatever.

I can't tell from the narration there if this is truly a special case, explicitly coded for by LW3dG, or if it arises naturally from the way that Bones normally work.