Dec 17 2005, 03:04 AM
I have a big iron ball attached to a chain with a dynamic constraint. The ball basically falls straight down to the length of the chain.
I would like to get that little upward "bounce" at the end when the ball hits the end of the length of the chain. You know what I mean? That sort of whip effect.
Currently... it gets to the end and sort of... swings around a bit but not realistically. Actually it gets to the end and doesn't move much but starts to pick up swing... then dies off... it just doesn't look "real".
I am hoping to achieve that sudden... upward "whip bounce" when something heavy attached to a "string" or chain hits the end.
I have only one constraint on the last bone of the chain with 0 stiffness and like... 400 mass. If I add stiffness then the ball doesn't fall straight down... it swings down.
Vernon "!" Zehr
Dec 17 2005, 05:28 AM
Maybe use some weights and springs?
Dec 17 2005, 11:37 AM
Could you bake the action and then add in the bounce by hand?
Or you could bake it and then, after the initial fall, raise it by hand as high as you want it to "bounce" then add a second dynamic constraint and leave it's enforcement at 0 until you're ready for it to drop again.
Dec 17 2005, 12:28 PM
How many times does this effect need to happen in your animation? Or is this a purely "how could I do this" exploration?
Dec 17 2005, 01:40 PM
I don't know if this would work for you - nor if you've already tried it - but have you tried changing the dynamic options targeting to spring? (from none, or constraint) & played with stiffness, drag, invisible collision objects?
(I haven't either, but I usually opt for spring, & turn gravity off, and model the chain in the final position)
Dec 17 2005, 08:06 PM
I have tried all the settings and came up with something that is pretty close.
Nancy, I need 0% stiffness to get the ball to fall straight down for my project. It needs to "free fall" to the length of the chain. The spring option is... too... springy. It continues to "wiggle"... plus... no whip bounce at the end.
It is the whip bounce at the end that kind of makes the chain and ball swing at the end. You get some slight "ripple" in the chain after the whip. You get a sort of "bowed" or wave type swing in the chain... the top and the weight at the bottom create a kind of... wave motion on the chain.
What I get no matter how hight the mass is that the ball conitnues to swing and flip up... more than it should.
I have a chain with a metal skull gearshift from my old car I am using as reference (don't ask).
A very high gravity in the chor makes the thing fall very nicely.. it is the "follow through" that kind of loses realism.
Robcat, this is a "real" project... but... well... it is a sort of a "promotion" of AM features with a comedic twist (poor thom)... I really want the absolute best results using the built in dynamic features... I don't want to use work-arounds if possible.
I've got the cloth... now I need the ball on the chain... that is the last obstacle.
I will continue to tweak settings. I am sure I will get it.
Vernon "!" Zehr
Dec 17 2005, 09:07 PM
I believe... maybe... possibly... there was some kind of... uh... er... user... error involved.
I was keying the dynamic bone at the end of the chain of frame 0 so that it was "at the top".
I "dragged" it up to above the end of the chain. On frame 1 all the bones were keyed "down". The simulation "seemed" to be doing the right thing... but... it wasn't.
Anyway... instead I deleted all the keys for all the bones except the dynamic bone with the constraint. I then keyed THE FIRST BONE in the chain by translating it up on frame 1.
...the ball goes flying up... because it has such a huge mass... it then comes straight down and the chain and ball behave exactly the way what I want them to...
All I do now is just use "use" the sequence starting where the ball is at the high point.
...dang ball! I'm the director dammit! Do what I say or you'll never work in this town again!
Phew... I feel good now.
Vernon "!" Zehr
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