advice on motion tracking

[pgraham]

Certainly it's possible to do this. I can't recommend any of those programs because all I've used is Maya Live.

The footage has "reference points" even though you didn't place any. Tracking software works fine as long as you can find some corners in your image. For example, you can pick points at the top and bottom of the airplane's tail, and at the top and bottom of the center of the front windshield. You can get a reference plane from any 4 points that share a common plane. More points are better. My example points share the vertical "YZ" plane in the center of the airplane. You have to tell the tracking software to constrain the track points to the YZ plane.

Once you've tracked the YZ plane, you will have a tracked camera that moves relative to the airplane. You can center the airbus on the YZ plane and render from the tracked camera.

[ahmedsheeraz]

I am a newbie in motion tracking and as far as I know, one should not track moving objects coz this ruined the motion solution. U said pick plane tail as a reference track, I dont know whether this is true or not coz plane is in motion.

[cryptosporidium]

ahmedsheeraz: depends on what do you want to track. if you would like to add something on the plane (a label for example), you would need to look for tracking points on the plane (you need the label move with plane, right?). but as far as i understood, philou needs only replace that plane with another one, larger, therefore smaller one will not be visible anymore. Then i dont see the reason for using any tracking software. Just place the new plane over the footage and do tracking manually since its quite simple and linear motion. No doubt if it doesnt match the original plane perfectly since you cant see it :)

[pgraham]

No doubt if it doesnt match the original plane perfectly since you cant see it :)The airplane needs to match the camera motion, at least to the point at which the viewer will believe it. The most sure way to make it believable is to match it with the original airplane.

Even if you didn't have an airplane in the footage, the camera may be rotating, so you'd have to rotate the virtual camera to match. You can get a believable camera rotation by tracking the mountains.

If there's no significant camera rotation, then yes, you could manually place the new airplane into the shot.

[cryptosporidium]

Well i thought its only panning camera shot. If its rotating, problem is slightly more difficult, but still i would track it by hand unless the footage isnt too long. Quick shots with linear motion are almost allways faster to track by hand. If you make autotrack, you still have to finetune it by hand in most cases (when you have no extra tracking reference). In the result its the same time consuming, but whats more important, its free - no more $$$ for additional tracking software ;-)

[pgraham]

Rotating is the same as panning. The issue I'm trying to get at is, if the airplane and the camera move independently, then you will get parallax on the airplane. If the camera pans, then you need to simulate the motion and render the airbus with the right amount of parallax to make the shot believable.

[philou]

Hi,

thanks for your responses & suggestions mates.
I have solved the problem by myself and a little help from Realviz MMtrack for Max (actually free of charge !!).
The shots (6 in total) were a little bit tricky because of the camera motion (panning+rotation )and the lenght (around 40 sec per shot). Now my A380 is flying in place of the "Corvette" and my boss is happy !!
PS : I have tracked and solved the shot in 2 pass, one for the background (animated cam), one for the Corvette (static cam-moving object)then merged the 2 scene, parented the moving object camera to the background cam and everything is OK now.
Thanks again,

Cheers,

philippe

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