4 Replies Latest reply on Sep 24, 2008 7:32 AM by Navarro Parker

    Is it possible to track this?


      Is it possible to track the "Car background" footage here:


      The "layered composite" from the above link is the end result that I would like to finish up with, with the (man_superimposed_png_ . mov) man in a stance on the roof of the car except that I would like the man to match the car's motion exactly. For the first 50 frames it's not too bad. I achieved this through painstaking time-consuming hand manipulation of scale and position.

      Is it possible to automatically track the motion of this car so that the man can seamlessly move and scale with it?

      I had a go at using this tutorial using the car_background_png_.mov footage:


      Which uses TrackerAverage_v1.1.jsx from here:

      http://aenhancers.com/viewtopic.php?f=9&t=136&p=1521&sid=e2f6387615bfc42e3a935239e2a6bea6# p1521

      The script takes the average of 4 trackers. I could get AE CS3 to put a tracker either the sides of the number plate (Which aren't in view for all the footage), the little dark dint at the top of the headlight on the left hand side of the footage and the right top corner of the headlight on the right side of the footage. None of the trackers are near where the man should stand on the roof of the car. I haven't found places near the roof for the trackers to go due to the specular reflections of the street lights on the shiny surfaces of the car. I took the average using the TrackerAverage_v1.1.jsx produces a path that is far too shallow for it to follow the roof of the car.

      Would any tracking method work on this piece of footage? What would work best? Would another peice of software be better? Please could you advise?

      Thank you for any advice.
        • 1. Re: Is it possible to track this?
          Level 1
          The biggest problem that I see in your car footage is that it's very dark and there isn't any single good tracking point on the footage that isn't effected by reflections or shadows or that stays in the frame. You may be able to use the bottom left corner of the cars' right headlight for most of the track.

          A tracker like Mocha might be able to do a fairly good job tracking the planes, but I'd tweak the footage first by increasing the brightness and contrast so there was more to track. I'd even tweak the footage if you were going to track in AE. You use the tweaked footage for tracking data only.

          The other option would be to stabilize the footage so that the car doesn't move, place your actor on the now stationary car and adjust his position and scale with a few keyframes, then remove the stabilization from the car and apply the inverse of the tracking data to the actor.

          I hope this helps.
          • 2. Re: Is it possible to track this?
            Mylenium Most Valuable Participant
            That's a tough call even for sophisticated software. Soem pre-processing to get a trackable version is surely required. In my view, the following steps are necessary:

            - Neutralize colors. Get rid of the greenish night-tint and increase contrast within what rests in the footage
            - Reduce the reflections from the lights. As they are more distinct than anything else, they surely will confuse any tracker.
            - Increase the contrast of the gaps/ lines defining the roof section.

            Once you have that, it should be easier to stabilize and track your footage. It will still not be a walk in the park, though. As an alternative to Rick's suggestion, you might consider reconstructing the camera in 3D. Automated matchmoving apps like Syntheyes work reasonably well even with low-contrast stuff...

            • 3. Re: Is it possible to track this?
              Level 1
              Reconstructing the camera is a good suggestion even though it's one that will require 3rd party apps.

              This project and the included footage brings up a great point, not about tracking, but about production planning. The key to pulling off any FX shot well enough that we'll suspend our disbelief is planning. Just a little more planning for the shot, just a little more control over the exposure so there was a little better image to start with, and the whole process would have been much easier.

              If it were me, I'd have shot at dusk and then graded the shot to night after the composite was made. I would also have had a fan of some kind blowing at the actor.

              If the tracking and matching is completed in a satisfactory manner then the next hardest part will be color matching the actor to the scene and the next to impossible part would be to make the clothing move in the wind. This points out, once again, the need for preproduction planning.
              • 4. Re: Is it possible to track this?
                Navarro Parker Level 3
                Definitely try Mocha/Mocha AE. There's no way AE's point tracker will be able to deal with this dark, low contrast footage.