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Animating an Emitter During Camera Pan

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Jeff Bellune
Animating an Emitter During Camera Pan
on May 21, 2006 at 2:10:54 pm

I have a sports video to edit and I want to add a cheesy particles-follow-the-ball effect to the video.

When the shot is locked-off, animating emitter position is no problem and the results are good.

But when the camera is panning to follow the action, I run into trouble.

To solve this issue, I have tried motion-tracking a feature in the frame of the video and applying the tracker position to the Particular solid layer, while at the same time animating the emitter


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Peder Norrby
Re: Animating an Emitter During Camera Pan
on May 21, 2006 at 2:59:49 pm

Why make it cheesy?

Anyway...
Trapcode Particular is a 3D Particle system. First I'd try and match move the camera, pan means the camera rotates. Throw in a few 3D solids and try to match the camera moves. Then add a 2D comp-sized solid for Trapcode Particular. (The solid for Particular should never be moved, always just sit still and cover the full comp). Then match the movement of the ball using keyframes for the Emitter.

Peder Norrby / Trapcode


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Jeff Bellune
Re: Animating an Emitter During Camera Pan
on May 21, 2006 at 5:09:10 pm

Hi Peder,

Thanks for responding. I'm not trying to make the effect "cheesy"; I'm just afraid that's how such an effect may be perceived by the AE/Trapcode community. :-)

The specific clip that I am using as a test bed has the ball moving with high velocity from right to left in the real world. The real-world camera is panning from right to left also, with a rotational speed that keeps the ball centered horizontally in the frame. The only movement of the ball in the frame is vertical as it travels on its downward arc.

When I keyframe the emitter's position to match the ball position, I get a vertical trail of particles. The trail has no horizontal velocity component, so the effect looks incomplete. I expect that, even with a camera pan, the horizontal velocity of the ball in the real-world would leave a trail of particles that had a horizontal velocity component.

Moving the camera's rotation or its POI didn't work. The vertical trail of particles moves in the frame, but there is no horizontal velocity component introduced by the camera's movement. I was not able to figure out how to use the 3d solids to manually match move the camera, so I had to resort to a simplified model with just an animated camera and a Particular emitter that moved vertically over time. I've probably omitted some steps or settings using the simplified model.

Moving the Particular solid layer does introduce a very nice horizontal velocity component, but you said I'm not supposed to do that.

Can you see where I've gone wrong? I'm hoping that match moving the camera isn't as involved as rotoscoping, but my research seems to indicate that it might be unless automatic match moving software is used.

Thanks,
-Jeff

The Focal Easy Guide to Adobe Encore DVD 2.0


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Peder Norrby
Re: Animating an Emitter During Camera Pan
on May 21, 2006 at 8:34:45 pm

Maybe you could just add some X wind to get the horizontal component. Physics>Air>Wind X

Peder Norrby / Trapcode


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Jeff Bellune
Re: Animating an Emitter During Camera Pan
on May 22, 2006 at 11:59:03 am

Peder and Mylenium,

Thank you for the input. I didn't realize that using Particular to create this effect would be as difficult as it is turning out to be. I was actually hoping to save some time by using Particular inside of AE as compared to using particleIllusion, which requires a couple of import/export steps to get the emitter's motion to match the ball's.

Thanks again for the ideas; I'll keep these techniques in mind for my 3D animations.

If anyone's interested, I've posted a short clip with the pI results. Here's the link (approx 220K): pI Demo clip

-Jeff

The Focal Easy Guide to Adobe Encore DVD 2.0


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Mylenium
Re: Animating an Emitter During Camera Pan
on May 22, 2006 at 6:08:31 am

your problem is that you don't really move the emitter much horizontally since you are only matching it to the footage and thus it more or less stays in the same place in AE's comp window. You'd have to try to recreate your realworld environment e.g. by using dummy layer to match certain elements and then physically create the motion, both of the emitter and the camera. You should find some reference frames and roughly stitch them together to see what area your pan encompasses. Using that large layer as a reference, you'd be able to reconstruct the motion of the ball. It would be doable by hand, but you might get quicker results using a 3D tracker such as PFTrack.

Mylenium

[Pour Myl


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Jeff Bellune
Re: Animating an Emitter During Camera Pan
on Jun 8, 2006 at 2:30:07 am

From the FYI desk:

I


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Peder Norrby
Re: Animating an Emitter During Camera Pan
on Jun 9, 2006 at 11:05:15 am

[Jeff Bellune] "What are the possible consequences of the method I have outlined above?"

Having a layer bigger than the comp can lead to unnecesarry render-time. It can also cause problems if trying to sync with other 3D graphics in the comp.

That said, if it works for you it does not really matter. I'm glad to hear you found a solution and thanks for posting it!

Peder Norrby / Trapcode


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