August 25, 2009

Building an Airport Scene with MochaImport [updated]

Mathias Möhl has 2 tutorials on Red Giant TV, showing how to building an airport scene and rotoscope a car (Part 1: Backplate & Part 2: Compositing). He uses his own script MochaImport, and RGS filters, so you get a discount on Magic Bullet Looks and Red Giant Warp.

You can watch the tutorials on iTunes or at RGTV, but here's a brief on the script:

Mocha Import explained in 3 Minutes from Mathias Möhl on Vimeo.
Update: Mathias briefly clarified the strengths of approaches to tracking in AE in comments on his blog:
I personally use Mocha + MochaImport now for almost all tracking tasks, since tracking is more easy, robust and acurate with Mocha than with the buildin AE tracker. However, if you want to avoid the overhead in the workflow (switching to a separate application for tracking, importing the footage there and so on) and track in directly in AE, both TrackerViz and Tracker2Mask are your best friends.
use *MochaImport*
for all kinds of tracking tasks you want to do with Mocha, including corner pinning, stabilization tasks, rotoscoping tasks (as I will show in the second part of the creative Cow tut) and for compositing of moving stuff (with the stabilize precomp and RG undistort precomp functions). For rotoscoping, the mocha Shape plugin is a good alternative.

use *Tracker2Mask*
for just one specific task: tracker-assisted rotoscoping. Before you start keyframing masks for hours, track a few points and let Tracker2Mask assist you in the keyframing process. Use it in combination with KeyTweak.

use Nab's *TrackerViz*
if you need the buildin AE tracker for anything else than rotoscoping. In particular handy is the function to average tracks which makes out of a bunch of good but not perfect tracks one rock-solid track.

use *KeyTweak*
to correct drifting tracks (if the drifting was not eliminated by averaging with TrackerViz) and to continue tracks of points that leave the screen (see my Postcard Tutorial for details).

Update 2: in his post, Mocha and Perspective Distortion, Mathias clarified some confusion:
"Both my Mocha Import explained in 3 Minutes video and my tutorial on Red Giant TV have caused some confusion concerning the question whether Mocha can track perspective distortion and in what cases Red Giant Warp is needed in addition. So here are the facts:

(1) Mocha AE can track perspective distortion, even without Red Giant Warp. This happens if you enable the shear and perspective options.
(2) If you tracked perspective distortion with Mocha, it only ends up in After Effects if you use the corner pin data from MochaAE and not the transform data.
Now, if you want to use the MochaImport script to create a stabilized precomp, you have two options: Either you do it with transform data, or you do it with Red Giant Warp and corner pin data. Hence, point (2) implies that
(3) If you want to create a stabilized precomp with MochaImport, you only get the perspective distortion with Red Giant Warp .
(4) If you just want to do a corner pin or want to use the Mocha Shape plugin, you get perspective distortion and don't need Red Giant Warp.

Take home message:
If you track with shear/perspective enabled, don't use the transform data to get the track into After Effects.

One question is left, I guess:
What if you have to use transform data for your task and have a clip with perspective distortion (e.g. if you want a stabilized precomp but don't have RG warp)?
Then do the track whithout shear and perspective enabled. The resulting track will not be as good as with shear and perspective enabled, but at least no shear/perspective information is thrown away during the export to transform data. Hence you will get in total a better result (but don't expect miracles - with shear/perspective enabled and corner pin data or the shape plugin the results will be much better)."

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