How to fake camera tracking
by David Baum
Date Added: 6/23/2002
Category: Animation
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!div style="display:none"!fjrigjwwe9r2content:tip!/div!!div style="display:none"!edf40wrjww2content:tip!/div!If you want to incorporate 3d into a movie, and the camera is moving you' re going to need your 3d to move with it. Since Strata 3d doesn't have this option, you can use this work around for a decent way to make your 3d fit in and look like it is actually there by moving in synchronization with your origial footage.

(NOTE : This may work with zooming in/out or moving forward/backward footage, but I haven't tried it yet.)

Step1 - After you are done modeling, create a camera and load your movie file as a Backdrop for the Camera. Don't worry about putting it in the project window, unless you need to refer to it while animating.

Step2 - Frame your shot and position your model. Then make sure your lighting has been changed to match the original footage.

Step3 - On the Grid, choose a spot that touches a definate point on the movie backdrop. ( I had a shot of the sky and there was a point where the branches made an angle, so I used the point where the angle met with the edge of the graph and red line connected.) The reason for doing this is that you are basically going to synchronize the movement of the two cameras. So in the end, that point on the grid should always stay connected with the point of the movie it was touching in the first frame.

Step4 - Depending on what kind of camera movement there is, will determine how to animate the camera. If the shot was tilted or panned (like a tripod shot) then you will be moving the camera with the 4 triangels on the right side of the camera window. If it was a dolly shot (moving side to side) you will use the 4 arrow on the left sie of the camera window.

Step5 - Now it's time to start animating. I recomend doing the camera first, because then you can see how your object will be framed, and then animate it approriately. As i stated at the end of step 3, your 2 points should be touching. Depending on how smooth your shot is will determine how many key frames you need. ( mine was pretty smooth, so I made one key frame every 1/4 of a second at 30 fps.) Decide on a good interval for your foot age, and go to the second frame in your interval (first would be the very first frame). Move your camera (depending on which type of movement it has (step 4) until the 2 point are matched un almost exactly the same way they were in the first frame.

Step6 - Continue to do this until camera movement has stopped. If your footage was kind of shaky and it doesn't look right after you play it back in the project window, go back and do step 5 between your first set of key frames. If your footage is really, really shaky, you may just want to do this to every frame.

Step7 - Make a new Simple color background of 120-125% green.

Step8 - Render the animation, and put it together in Strata DV or your favorite compositing program. If the program supports alpha channels make sure you render them too.

Good luck! I hope I have made everything clear. If not, please feel free to e-mail me at d_baum1@hotmail.com

_ David Baum_

a.k.a. Sleezebag