After Effects: Always orient towards 3D camera with NO perspective shift?

[brandonb96942845]

Need a little help with a fairly basic issue. Short version, I have a piece of footage that I want to motion-track some objects into using the "Track 3D Camera" function. I've set "always orient towards camera" option, but it's not working quite the way I need it to.

What I've got is two additional pieces of footage inserted into the comp with the 3D option enabled, and when the camera moves the 3D objects for the imported footage show definite perspective shift. What I'm aiming for is for them to always orient directly towards the camera and, from the camera's perspective, to have zero perspective shift. (I'd use the standard motion tracker for this, but the footage pans through almost 230 degrees, so there's more camera motion to track than the standard motion tracker can handle.)

Help???

[Mylenium]

AE has no ortographic camera, so there'll always be perspective shift. Presumably you'd have to use a completely different approach like keeping the layers 2D and writing your own expressions to transform them while they are pinned to 3D Nulls using layer space transforms. Anyway, impossible to say anything specific without at least a screenshot.

Mylenium

[Rick Gerard]

You have a couple of issues with Camera Tracking and a panning shot. First, if the Camera tracker decides the shot is a pan, there is no depth information in the track. You can get exactly the same information as you get with a track in Mocha AE. I always use Mocha to track anything in a panning shot. It is a lot better for that kind of thing. You can track translation only (position) or translation, scale, rotation, skew, and perspective. It's also very easy to track surfaces until they go off-screen or manually adjust a track that fails. Try using Mocha AE instead of Camera Track.

If that completely fails, we need to see screenshots or, even better, the video you are trying to track.

Mocha AE Training

[brandonb96942845]

I didn't even think about using Mocha--that's a good idea though, I'll give it a try.

If it doesn't work I'll update this thread with a clip of the sequence I'm trying to assemble.

[brandonb96942845 · Accepted solution]

I think I've actually come up with a simpler solution than going through Mocha--it occurred to me that if I could rotate the 3D objects for the imported clips to match the camera, all I'd really need to do would be to rotate them on a continuing basis.

And since the 3D camera itself was providing rotation information (or more accurately orientation information), no reason not to use that.

So the answer turned out to be to set the X/Y/Z rotation on the 3D clips I'd imported all to zero, then parent their orientation to that of the camera. I thought I'd have to do some complicated math, but just a straight-up parenting of the orientation values did the trick.

So to anyone out there looking for an orthographic camera, here's a workaround that basically gets it for you. Once you parent the orientation, you can then add any custom rotation to the child object you might want.