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Why Does My Rollercoaster Flip ? (see My Scene)

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rackam_blue
Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 22, 2006 at 3:12:22 pm

Hi all,

I need help too fix a problem. I try to make a simple rollercoaster but the cars always flip on the curve. I've got the same problem either when i use motion path or ik spline.

It has something to do with the tangent of the curve.

See my scene http://sauge1.free.fr/test.mb

Of course with an ik spline you can use the "roll" attribute to fix the problem or the "twist" with motion path but i what i really wonder is if there is is a clean way to do it instead. A way with no flip to deal with.

This problem always occurs when you want to make a motion path or ik spline with an "extreme" curve and i've never been able to fix it and nobody yet could tell me how.

I know that i could use the pointOnSurface technique but it's not very handy for a rollercoaster for example. Moreover i'm sure there is a easiest way.


Thanks a lot for your help.


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Jason Brummett
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 23, 2006 at 4:25:48 pm

this is a tricky one in Maya but it does work if you take the time to setup it up. Search highend3d for "flipping" or something similar.

The most straight forward way is to assign an object as your up node vector. For instance, you can take the path your animating on and duplicate it or offset it along a vector and place a dummy/locator on this path and give it the same animation keys you already have for your main object. Now you can assign the up vector as an object and pick the object on the second path (the locator) and your main object will always aim towards it.

Jason Brummett
Studio Z Inc.


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Jason Brummett
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 23, 2006 at 4:56:19 pm

BTW: when posting a scene file from Maya, it's a good idea to explain what version of Maya it came from and also it's easier to open if it's saved in *.ma format instead of *.mb.

Cheers,

Jason Brummett
Studio Z Inc.


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rackam_blue
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 23, 2006 at 5:11:11 pm

Hello Jason,

You are perfectly right.
A guy on CG talk gave me the same solution as you and it works nicely.
It's real pleasure to speak with people who knows what they are talking about.

Thanks a lot.
R.




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mYthprod
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 26, 2006 at 3:21:57 am

Rackam - can you do a quick step by step? I tried repeating what you guys were talking about and even tracked down the post over at cgtalk and still can't reproduce. My test objects were a simple CV curve and a beveled letter A. I assigned my letter A's motionpath's world up type to object and typed in the name of my locator but it's ignoring that I did that, it seems.

I've run into this problem before and would love to learn this technique.



- MythProd
(John David Hutton)

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Jason Brummett
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 26, 2006 at 4:14:05 am

Here's an example Maya 7 scene (*.ma) using an A shape as requested...

download from my website at this location: http://stzgraphics.com/creativecow/

Didn't have to tweak it at all (got lucky) :) I assigned an locator to an offset curve shape (deleted history, and transforms) on all shapes before I did the motion path node.

Is this what your trying to do? If so, hope it helps,



Jason Brummett
Studio Z Inc.


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rackam_blue
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 28, 2006 at 7:11:04 pm

Yep, that's it.
Thanks again John.
R.


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Jason Brummett
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 28, 2006 at 7:17:18 pm

your welcome Yellow!

Just joking.

Jason Brummett
Studio Z Inc.


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Jason Brummett
Re: Why Does My Rollercoaster Flip ? (see My Scene)
on Sep 28, 2006 at 7:27:48 pm

Whoops. Must have ment John Hutton. he he.

Jason Brummett
Studio Z Inc.


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