Just updated to After Effects CS4. The lack of motion blur for corner-pinning in AE makes the whole Mocha / AE setup fairly useless, but since Mocha is such a great tracker, it was worth working out how to add motion blur in AE from the corner-pin data. So here’s a link to an After Effects favourite that does just that with a directional blur. The expressions only deal with planar motion-blur, which is good enough for most shots (i.e.those that don’t crash-zoom).
A few notes on how to use it: Copy and paste your corner-pin tracking data from Mocha, and paste it onto your layer in AE as usual. This adds a corner-pin effect to your layer. Then apply this MB_for_Mocha favourite to the same layer. This adds a directional blur effect linked to the corner-pinning. All you need to do now is match the amount of blurring. Move on to a frame in the timeline where you have lots of movement. In the directional blur effect in the timeline, drag the ‘Blur length’ up until the amount of FG blur matches your BG shot (about 150 works for me). The ‘Blur length’ will pop back down to 0.3 or so - that’s because it’s calculating the blur based on the amount that you just gave it divided by the amount of movement for that particular frame.
Presto! Motion blur!