Floppy spline?

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Old 01 January 2013   #1
Floppy spline?

I'm trying to get a spline to where I can grab one end and shake it and the other end will flop about. Think of it like a lizard tail or floppy asparagus. This is easily done with a simple joint chain and IK tag and the floppiness is controlled by the joint strength. I'm not seeing any clear way to control a spline like this. Spline IK has no dynamics and Hair Spline dynamics has no control like the Strength feature that controls the rotation strength at each vertices. Am I missing something or is this not possible with splines?

Thanks!
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Old 01 January 2013   #2
not so sure if i understand you correctly. you want to have a a stiff chain where only
the start and the end are being loose and when you 'flip' the start segment the
momentum is being transfered trough the chain, so that the last element - the end -
'flops' ?

as a stupid side question by someone who never did CA - if it is so easy with joints,
why don't you use them, are joints restricted to polygon objects ? and if it is so
wouldn't it be asy to create a polyon dummy for your spline and then just map the
spline points onto the polygon dummy ?
 
Old 01 January 2013   #3
 
Old 01 January 2013   #4
@Little devil, well, you can't use joints to manipulate a spline without spline IK and Spline Dynamics pretty much turns spline points into joints. Problem is neither one has dynamics where you can limit things like joint rotation with dynamics. Mapping a spline to a proxy mesh can work, possibly, but seems like there should be an easier solution.

@Jeremy, imagine rotating the sphere so the tail is sticking straight out to the side, then grabbing the sphere and shaking it up and down to make it flop like a tail. I'll upload a simple scene using a basic joint chain to demonstrate.

Thanks guys!

T
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Old 01 January 2013   #5
Here's a sample scene with a simple joint chain.
Attached Files
File Type: zip FloppyChain.c4d.zip (63.3 KB, 34 views)
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Old 01 January 2013   #6
how about with an extra constraint:
https://dl.dropbox.com/u/4480607/Sp...cs_JW_2.c4d.zip
 
Old 01 January 2013   #7
Quote:
Originally Posted by JeremyW
how about with an extra constraint:
https://dl.dropbox.com/u/4480607/Sp...cs_JW_2.c4d.zip


That's close, but not really like a tail like you get with your basic joint chain. No simple solution or obvious setting I was overlooking. Thanks Jeremy!

T
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Old 01 January 2013   #8
Just for the fun of it... exactly how is it close and how is it not close? With some tweaking, this could be refined to solve your problem.
If you are put off by the stiffness at the base of my rig (due to stationary second constraint sphere), we could add some secondary movement to constraint 2, or just the illusion of secondary movement by limiting the constraint2's influence.
Placement of the second constraint (closer to the base) would also reap considerable nuance.
Just sayin'
 
Old 01 January 2013   #9
Using the Hair Object?
Generating a single spline, having
the Guide with few segments and
the hair spline more segments.

FloppyEnough?

Cheers
Lennart
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Old 01 January 2013   #10
Quote:
Originally Posted by JeremyW
Just for the fun of it... exactly how is it close and how is it not close? With some tweaking, this could be refined to solve your problem.
If you are put off by the stiffness at the base of my rig (due to stationary second constraint sphere), we could add some secondary movement to constraint 2, or just the illusion of secondary movement by limiting the constraint2's influence.
Placement of the second constraint (closer to the base) would also reap considerable nuance.
Just sayin'


Well, what I was trying to figure out is if there was a quick way that I was overlooking to create the same dynamic effect you get with the simple IK tag and joint chain. With enough time and tweaking I'm sure you could create a similar affect, like you are pointing out. I was just trying to determine how much time I would have to invest into it to get the effect I was going for.

Thanks Jeremy

T
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Old 01 January 2013   #11
Which version of C4D do you have?

The later versions have a Dynamics option inside the IK Tag, letting you go from standard IK behavior to a dynamic chain. You can probably use colliders to guide the chain's behavior.

A simpler setup I normally use for tail-like movement is instead of IK Tags, I just use a chain of Spring Constraints (with gravity set to a nonzero value) following my controller. That way each successive spring target gets droopier than the last.
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Old 01 January 2013   #12
Quote:
Originally Posted by tcastudios
Using the Hair Object?
Generating a single spline, having
the Guide with few segments and
the hair spline more segments.

FloppyEnough?

Cheers
Lennart

Yes, that's great. Now how do I use that spline for things like Spline Wrap and things I want to use an actual spline for?

Thanks Lennart
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Old 01 January 2013   #13
Quote:
Originally Posted by rustEdge
Which version of C4D do you have?

The later versions have a Dynamics option inside the IK Tag, letting you go from standard IK behavior to a dynamic chain. You can probably use colliders to guide the chain's behavior.

A simpler setup I normally use for tail-like movement is instead of IK Tags, I just use a chain of Spring Constraints (with gravity set to a nonzero value) following my controller. That way each successive spring target gets droopier than the last.


Yes, on the regular IK tag, that's true. You can't use that on a spline. I want to apply that functionality to a spline that I can then do other spline related things with.
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Old 01 January 2013   #14
Quote:
Originally Posted by rustEdge
A simpler setup I normally use for tail-like movement is instead of IK Tags, I just use a chain of Spring Constraints (with gravity set to a nonzero value) following my controller. That way each successive spring target gets droopier than the last.


Hmm, that's an interesting approach. I haven't used springs for anything yet. I'll have to look into that. As long as I can apply a spring to different sections of a spline, that would work.
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Old 01 January 2013   #15
Quote:
Originally Posted by Troyan
Yes, that's great. Now how do I use that spline for things like Spline Wrap and things I want to use an actual spline for?

Thanks Lennart


The Hair Object is set to make a spline,
so I don't see the issue?

Otoh, if want to work with a regular spline,
you can use the same idea the Hair Object does
keeping the main direction of the spline by "locking"
the first two points to its parent.
Tuck a low point spline under i.e.a Null,
select the first two points and fix them
in the Hair Dynamic Tag.

See Here

Cheers
Lennart
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