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Is this 2D track possible?

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Ben Davis
Is this 2D track possible?
on Mar 26, 2010 at 11:00:31 pm

I'm creating a short film that basically involves a meteorite thing smashing down in a car park (I promise there's a little more story that that!) The shot I'm working on involves a guy, having been pushed to the floor by the impact, getting up and turning around to find a giant metal sphere thing embedded within the ground. The sphere I've created in 3D and rendered out as a single frame. I took the render into photoshop and then painted in lots of rubble and cracked concrete, I then imported this PSD into an after effects composition. This was all done under the slightly naive illusion that this composition could be tracked into the shot using the 2D tracker (I originally planned to matchmove the shot but I had many problems trying to do that). I had originally thought that because the camera move involved relatively little parallax a 2D track was possible. I thought I could just track two points for position, rotation and scale and then apply this to the PSD. However it doesn't seem to be as simple as that.

Here is the plate I've been working from:

Here's the PSD I'm using:

And here's what I like them to look like when composited together:

So is it possible or would a 3D track be the only option? Thanks to anyone who replies, I really really need the help!

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Joey Foreman
Re: Is this 2D track possible?
on Mar 27, 2010 at 12:56:30 am

You didn't specify which version of AE you have, but if you have 9, I strongly suggest taking a couple of hours to learn Mocha AE.
If you don't have 9, download the demo, learn it, and try it with your shot.

Mocha tracks planes of patterns, rather than points, and the results, when used properly, are usually rather phenomenal.

What Mocha isn't going to be able to help you with, though, is the parallax shift that would occur with 3d objects from a free-floating camera move such as yours that is basically a combination track-in and rotation without a fixed nodal point.

Mocha would have no trouble with this scene if you were trying to place a flat object on the ground, or the wall of the building. A 3d object is another kettle of fish. But i think it's worth trying anyway to see if you can get away it.

If it doesn't sell, then yea, you'll need a 3d tracker like Syntheyes or Boujou. The problem there, though, is you didn't set up any tracking markers for one of those apps to work with, so the program will struggle to find enough points that remain in the frame long enough to extrapolate an accurate track.

I don't know if anyone has developed a 3d planar, as opposed to point, tracker, but that would save this shot.

BTW, I guess you're planning to rotoscope the talent as he approaches the object? Not impossible, but set aside a day or two for it.

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Alperen T. Ayhan
Re: Is this 2D track possible?
on Mar 27, 2010 at 10:15:04 pm

I have dowloaded your files and tried to do it with after effects' trackers but I couldn't find any definite points to track. So Joey is right, you should use definitely mocha.. you may know about it but here is some very helpful video tutorial links:

Alperen T. AYHAN
Always cinema...

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