zoom lens tracking with boujou

[Anonymous]

hi.. i need to 3d-track a shot that starts with a fixed camera but in the
end of the shot (approaching a window on a building) the camera starts to zoom to get closer…this will inevitably f**k up the track.. is there any way or workaround for doing this in boujou or matchmover..?

/S

[Rayk]

hi,

don’t know boujou or matchmover, I use scenegenie for 3d tracking. anyway. forgive me when i ask the obvious, but is the camera move very shaky and/or is it a dolly/track shot? did the camera has came to still stand befor it is zooming in? does the camera zooms into the room through the window or is the window just starting to fill the frame?

have you already tried to track the shot backward?

best,
-rayk

[Anonymous]

hi rayK…

nope, the shot is a very smooth fly-in from a heli..it never comes to a still..there’s just a smooth transition from being fixed to zooming in towards the window..they had to zoom to get as close as possible to the window as they werent allowed to fly any closer to the building…in the final shot its supposed to look as were flying through the window in to the room but that has to be done with some 3d and stuff (and basically has already been taken care of..) the tricky thing is not to get weird parallax when the zooming occurs..i havent tracked it backwards yet but i suppose that might give some more info for the tracker…

btw: what is scenegenie…standalone app or some discreet thing or?

thanks //S

[Rayk]

hi sammo,

scenegenie is a plug-in for 3dsmax. it is build of http://www.afx.com.
have also a look at http://www.ssontech.com , maker of syntheyes – similar to scenegenie, but standalone PLUS automatic tracking.

what also comes to my mind is, when later, the fly-in ins done by 3d anyway, why not just stop tracking before the zoom-in? and make a smoth transition in the 3d app? you need probeably need stableizing the zooming in part of the footage for later comping.

good luck,
-rayk

[Anonymous]

Hi.
If I get it right, you’ve got a fixed cam, with focal variation…
In such a case, and with no extra info (mesurements, etc.), from what I’ve learned, Boujou might be te exact solution.
Just activate the “nodal pan mode” (since the cam is fixed), and specify your camera to fave “variable unknown” focal…
Let the magic do !
If you’re auto-tracking, don’t forget to mask any moving objets (heli, etc.). In such a case, though, when the footage is to complex for autotracking (moving objects, etc…), I do my 2D tracking manually, in boujou, or any other 2D package that exports 2d tracks in a text format (shake, Matchmover’s rz2), etc…
Good luck.

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