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poor texture conditions to use 3D camera tracking

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Philippe Gerard
poor texture conditions to use 3D camera tracking
on Dec 24, 2015 at 3:46:49 pm

I tried to look for an answer to this following questions, but didnt see a similar problem.

Well, i have to change the sky of a sequence using an high res jpeg.
this looks simple with a 3D camera tracking since i just want to track a part of the film and replace the background.
But the thing gets much more complex, knowing that all the part of this sequences are moving in different way ( a guy is talking, seated on a boat and camera is moving, so the sky is behind that guy). the second problem is the sky is burnt, this is why i want to change it. the only traking that doesnt fail is a mask tracking made on adjustment layer with a mask selecting only the part of sky visible.
i would love to take the motion of this adjustment mask to animate the jpeg file of new sky.

the guy has already been roto brushed, i just need to animate the moving sky behind him.

thanks for your help
Warm regards


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Dave LaRonde
Re: poor texture conditions to use 3D camera tracking
on Dec 24, 2015 at 4:48:53 pm

I don't know if you even need to motion track it. You'd probably be able to get away with moving the sky by hand.

I'd be more worried about the light wrap caused by the previous sky on the rotoed stuff in the foreground.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Philippe Gerard
Re: poor texture conditions to use 3D camera tracking
on Dec 24, 2015 at 5:27:58 pm

Hello Dave

thank you. In fact because the shot is on a boat, animating the sky by hand is not really good, because the movement of the boat makes a combined rotation and translation. The mask tracking is much better than my frame per frame animation.

Regarding the lighting, i dont change much the light. the guy was in front a burnt white sky and i replaced with a cloudy sky (still white but with details this time)

Thank you


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Dave LaRonde
Re: poor texture conditions to use 3D camera tracking
on Dec 24, 2015 at 6:07:16 pm
Last Edited By Dave LaRonde on Dec 24, 2015 at 6:59:51 pm

I'm trying to figure out exactly what you're tracking, and I'm not having much luck.

Tracking anything on the boat won't work -- the boat itself is moving.
Tracking the sky, which would have information about its movement, won't work -- it's blown out, and there's no detail.

So what are you tracking?

If you can't do a track, you're left with simulating it by hand. Since it doesn't seem that there's much of a reference to indicate that the simulation is off, it could be easy to fake.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Philippe Gerard
Re: poor texture conditions to use 3D camera tracking
on Dec 24, 2015 at 11:48:28 pm

In fact when using the mask tracker, it seems like there is still a residual texture in the sky and the horizon (the edge of sea and sky), sounds enough to give a good result with that tool.
the tracking of that residual texture is working good. but the problem is that you obtain a shape mask over time and not a position and rotation value that i can apply to the new sky image. if i copy the
shape mask tracked to the sky i obtain just a good shape following the movement, not a movement on the new sky.
Is there a way to tansform a mask shape into position and rotation data?


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Philippe Gerard
Re: poor texture conditions to use 3D camera tracking
on Dec 25, 2015 at 12:20:35 am

Here, i think an image is better to explain.


the pink area is mask tracking from an adjustment layer that modify the hue in pink, the surface tracked is perfect for the 14 seconds of this shot. it apparently use the texture to track and not contrast feature points i suppose.
now the problem having this mask path doesnt give me a position and rotation for the picture of sky to animate.


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