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Rotating 3-D emitter

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Patrick McMurtry
Rotating 3-D emitter
on Dec 15, 2009 at 4:37:11 pm

I have a 3-D emitter, set to sphere, arrangement = outline. I populate the surface with a cell (basic blur) using a large initial particle number and have birthrate and velocity = 0. I want to rotate the emitter so it looks like a rotating sphere. When I scrub through the y - rotation in the properties tab of the inspector, I see exactly what I want. However, when I animate y-rotation with either keyframes or using the rate parameter behavior, all I see when I preview is the wireframe of the emitter rotate with the actual sphere stationary. (Same is true if I apply the rotation to the group and set it as a 3-D group). I see the rotation values progress in the properties tab of the inspector, but as I mentioned, only the wire frame rotates. Also if I export it out, there is no rotation. I've used motion enough to usually be able to figure out some quirks, but this one has me baffled. I've tried all the standard tricks when motion is acting funny. Is it a motion bug, a problem with my computer, or, most likely, a problem with me? if I apply a camera with a sweep behavior, I can get the animation I desire for a single sphere, but I want to have multiple spheres rotating at different rates.

By the way, I got this basic idea from Zak Peric's interesting Diamond Sphere tutorial on embryo.me.uk

Thanks for any ideas.
Pat


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Mikey Bouchereau
Re: otating 3-D emitter
on Dec 18, 2009 at 1:02:41 pm

I've seen this way too many times. When you are not playing your clip and you are changing the rotation of the emitter, all it's doing is re-drawing where the particles should be at that point in time. It's not actually moving them. Basically once a particle is born the properties you adjust to the emitter do not effect it. So you can't do what you are trying to do at least not that way.

Now the way to effect this particles after they are born, is by placing them in a new group (3D) and applying that Y-axis rotition to the group. Making everything in that group move on the y-axis. Before you apply that animation to the group make sure that the anchor point of the group is in the center of your sphear. Otherwise you will get a orbiting sphear not a spinning sphear.

Hopefully that makes sense. Even though I know this I always waste a few min bashing my head against my desk because I can see what I want but it won't animate it. Then I remember you need to put the element in a group and apply the movement to the group.


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Patrick McMurtry
Re: otating 3-D emitter
on Dec 18, 2009 at 2:47:37 pm

Thanks for the tip Mikey,

I tried doing some rotating of the group without the exact success I was looking for, but I probably could have given that more time. I'll play around more with your suggestions as I want to understand this better. In case you are interested, the solution that worked for me was to add a transparent object at the center of the emitter, and then add then apply the "orbit around" behavior to the emitter (X and Z axis checked for my case), with this null object as the source. It gave the behavior I wanted and I can now nest different particle generated spheres inside of each other with different rotations. It is still curious to me that I can scrub the parameter and see what I want in the canvas, but not animate in during playback. Your description helped me come to terms with that.
A useful short description of this from discussions.apple .com is at
http://discussions.apple.com/thread.jspa?threadID=2267763&tstart=0

Thanks again for your helpful comment. Pat


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