motion path and flipping

[svenip]

i always tend to break up the rotation values on the path animated object. then only the translate attributes are controlled by the path. after that i go and use the tangent constraint on the path animated object. which always seem to work more correct then the settings within the path animation. even it does the same.

[yeepeee]

Hi Svenip,

Unfortunatly it doesn't work...
I can't beleive that no body knows how to fix this problem cause motion path is so a simple and usefull function.
Amazing.

But we'll find for sure.

Thanks a lot.

Yeepeee.

[svenip]

hmm that's strange. for me this is always the solution. ok we can try something different at last. the flipping should occur on the seam of the curve (means where the start and end point of the curve is). so you could try to moove the seem to a total different point. right click on the curve select curve point and select a point on the curve (wherever). then go to edit curve-moove seem.

that's the only thing what comes in mind to me right now.

can you describe how did you set up the whole anim ?? maybe gibe the file ? then it's a lot easier to see what's wrong.

[bigfatMELon]

Originally posted by yeepeee

Unfortunatly it doesn't work...
I can't beleive that no body knows how to fix this problem cause motion path is so a simple and usefull function.
Amazing.



The fact is that your object must flip/twist at whenever you use a periodic path. This is because the rotations are based on euler angles. Once your object reaches the 360 degree mark on the circle, and the very next point on the curve being zero, means that the eulers are going to flip back to their original orientation. If you made the circle as an unclosed spiral that was squashed to the point that it looked like a circle, this problem would be elimiated, tho you would also then have a fixed number of times that you could go through the loop.

I would consider what has already been mentioned and use the loop wire only for position. I would do this by animating a null along the wire and point constraining to that. Since this IS a perfect circle, the deformation is a constant and an aim constraint toward the center might also work nicely to keep the orientation.

In fact, given that it is a circle, I have to question the use of the wire at all if not just to test the feature. You could just offset from a rotating null.

-jl

[yeepeee]

Thanks for your good advices Melon,

In fact the circle is just an exemple my real curve as you can see is much more complicated.
You are right the prob come from an Euler computation of the path and I don't understand why Alias don't give the choice between Euler and Quarterion computation, because Quarterion does exist in Maya.
Surely it's possible to make a mel script that use quarterion computation to make a motion path, or at least unflip the object automaticly when it pass by a flipping area.
But unfortunatly it's far from my poor mel scripting knowledge.

B. r.

Yeepeee.

[bigfatMELon]

By separating the position from the orientation with various constraints, you can not only get around the problem but also build a more robust and flexible rig. Even given quaternians, I would still build it on constrained nulls for the flexibility alone. Sometimes what seems like the work around really ends up being the right path all along.

-jl

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