So this is the feature I was most looking forward to in FCPS6 since most of the video work is in slow motion (usually abt. 30%). Two things are happening and when I try to enable optical flow:
1) if I try to send the video from FCP timeline, it launches motion but an error comes up that says: "the following items used to create this project are missing - Item A, Kind: Media" and then there's a canvas w/a red & white checkerboard underneath. I've tried this on 2 systems and get the same error.
so to work around this I
2) rendered out my slow-mo'd clip in FCP and exported it as a self contained QT movie and brought it into Motion. Then I enabled the optical flow option in the inspector. The wheel popped up (the one that shows up when you start your computer) next to the record button and I could hear my system working away. It took forever... like 5 minutes... for the wheel to go away which is scary because I'm running this on an 8core mac w/a ATI Radeon graphics card and clip is only 30 seconds long! WTF? Anyway, the preview wasn't any better than the FCP version. I rendered it out, brought it in FCP so I could do a side by side comparison and I was right... they both still look like crap which means (I hope) that I'm doing something wrong and the optical flow didn't kick in. Help!
At NAB, one of the apple guys demonstrated how you can take an entire timeline already slow-mo'd in FCP quickly to motion to enable optical flow and then render in FCP. Well, that won't work for me if I can't solve the problem in #1! Plus, it's no good if I can't get the optical flow to work right anyway - hence problem #2! Any ideas???
I don't know what you're encountering in #1, but the long processing time you experienced isn't unusual. Optical flow analysis means following the motion paths of every pixel in the image. A 30-second clip would definitely take some time, whcih is why Motion processes it in the background for you.