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[Sidefx-houdini-list] wires dynamic problem
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Guillaume Laforge 2009년 1월 16일 (금) 오전 3:15
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Hello,

I'm working on a simple DOP wire simulation. The setup is just one curve
(rather long).
At SOP level, the root of the curve is constrained on a keyframe animation.
In my DOP network, I'm using "Use Deforming Geometry" in the Wire Object.
I use a SBD Pin Constraint on the root points ( 0-3 ) and then check
"Constrain To Animation" to keep
the SOP animation on the 0-3 points.

My problem is that I can't find a way to avoid some stretching between
the pin points and the first point moved by the wire solver.
To limit the stretching, I set a high value on the Linear Spring
Constant. It works fine for all the points, except
between the "pin points" and the "solved points".

Any tips to stop this stretching is welcome.

Cheers

--
Guillaume Laforge
3d Technical Director

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Mark Story 2009년 1월 16일 (금) 오전 4:09
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Hmmm ... that's odd. I don't know if it would be a reasonable work
around, but you can assign those attributes as a point attr and dial in
the exact mount of stretching/bending you need along the length of the wire.

The particular behavior you describe I've never encountered before,
(I've done a lot of work with Wire DOPs) but am interested in what might
be happening ... if you can't solve the problem, please post a hip file
on one of the forums so we can take a look.

Good luck!

Mark

> I'm working on a simple DOP wire simulation. The setup is just one curve
> (rather long).
> At SOP level, the root of the curve is constrained on a keyframe animation.
> In my DOP network, I'm using "Use Deforming Geometry" in the Wire Object.
> I use a SBD Pin Constraint on the root points ( 0-3 ) and then check
> "Constrain To Animation" to keep
> the SOP animation on the 0-3 points.
>
> My problem is that I can't find a way to avoid some stretching between
> the pin points and the first point moved by the wire solver.
> To limit the stretching, I set a high value on the Linear Spring
> Constant. It works fine for all the points, except
> between the "pin points" and the "solved points".
>
> Any tips to stop this stretching is welcome.
>
> Cheers
>

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Guillaume Laforge 2009년 1월 16일 (금) 오전 4:24
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2009년 1월 16일 (금) 오전 6:18
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Yes, I just found the solution :).

Only the first point of my wire was animated by hand in SOP. I added this
animation to all the points instead
of just the first one and now it works perfectly !

I found the problem because I didn't understand why the wire dynamics
worked well on previous work with some fur animations.
I realized that each fur guides sent to the DOP was moving from root to tip
points (as animation came from the copy sop
template input).

In my current work, I was copying the animation of a character hand on the
first point of a curve/wire, thinking that all the
other points will be animated by the wire solver. Good to know (for me at
least :) ) !

Cheers

Guillaume

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