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Jason

Challenge: Helical cable

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Hi guys,

Here is a challenge for you all: how do you make a good system for a helical cable; like telephone cord or like a slinky dog? The challenge is to come up with a good system where the user can specify two ends and the centre section droops realistically. The more intuitive artist controls and system stability are of utmost importance for this type of system in production. We don't want to struggle endlessly with the behaviour and the look of the droop. Secondary animation is also a bonus.

How about that? Think of the Slinky dog in Toy Story, or a character on the telephone.

Sound good?

Lets do it!

Jason

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I have another entry from a submittor that describes the caternary curve and the spirals completely in VEX; a really clever entry indeed.

Can we peek at each others' answers now? ;)

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This the first that has come to mind.

The second arrival was also... But here has left a "LockOn" demo.

Just open scene and hit play. (6.1.128)

Bypas "add_secondary_motion" node to edit endpoints.

Not so clever...i know...sorry guys...

i cant shake it...damn i`m hit...Eject...Eject

cord.zip

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I slightly modified the file to use some CHOPs instead of the Expressions, since, it's faster. But, this is still the brute force approach. I know, I know... Doctor Aizenk Houdini won't be too happy with this "solution". :)

PS.Andrew, I hope the ejection was done by K-36, so, you'll be able to fly again in a month or so. :)

helical_cable.zip

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SOPs & CHOPs

OK, gentlemen, I didn't like much the elegancy of my first attempt. So, having borrowed a couple of ideas from Andrew V.K.'s solution, I came up with this hybrid one, which is very simple, but good enough to achieve the goal.

There is no MIN/MAX limits, so, it is up to an artist to keep the look believable.

P.S. IMHO, Jason, a telephone cord and a slinky dog are not quite similar in behavior. So, it's much easier to make two kinds of springs for animation, instead of trying to fit both in the same shoes. But, it's just IMHO.

spring_cord.zip

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D`n`D taki da K36 vinesla :)

U tebia v point2 sop ostalsia expression

kotorii ne praciue. On ispolzuet stamp

fichu kotoraia stampit rastiazhku individualnogo

segmenta kotoraia raschitivalas v vex builder.

Poskolku takogo atributa u tebia net to etot point sop

prosto rastiagivaet ego na 1...no join

taki delaet svoe delo...hotia na extrimalnoi

rastiazhke budet zametno.

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Yeah, Andrew you are right. I left that expression in Point2 SOP by mistake (just overlooked it). If one replaces that expression with $TZ, it will look more cosher (the SOP, I mean).

And the other thing, you are right about too. The spring stretched to extreme won't look good, but I hope that animators will use their common sense.

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Here is a reply that I received that does it by describing a catenary curve in VEX and then adding some noise and waves to it. A very simple and very effective solution.

Take a look!

wobble.hip.gz

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Heres my little go at it. Its just a lattice controlled by a nurbs curve that is a softbody. There is one problem though. The top and bottom end points are in their own groups. I have transforms on both groups but the problem is that bottom group will move and deform right but the top group won't move at all.

cord.tif

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