How easy in Fusion to replace a background?

Hi,

I had a shoot recently where the location I thought I was going to get, a meeting room on the top floor of an office tower block with a lovely vista, turned out to be a meeting room on the 1st floor. The background was horrible; some steel girders and ugly grey metal things behind the actors.

What would be a recommended workflow to replace the background using Fusion?


Thanks for any help,
Jules

[Steve Roberts]

These types of shots can be done in Fusion. However these will be fair bit of work.
Without seeing the shots it would be hard to say what is involved. Like are the camera pretty static, or are they moving a lot for example.

How long is the shots? how many people in the shots?

I agree. In case the camera moves 3d track it (Syntheyes for example).
Than imported in Fusion you can project the camera back onto a plane or similar.
The benefit is for all the stuff in the window you can draw simple masks and they stay rather consistent.

EDIT: Just to make it clear: 3D Track -> Project camera on geometry at different times -> UV unwarp -> Paint masks -> apply texture back to geometry -> film everything back from the 3D tracked camera.
With this setup you can add background plates. As you will have a real 3D moving camera you will have all benefits like parallax on the background.
This is not a one day shot, but if you treat the 3d env correctly you might get away with the same setup for multiple shots / 3d tracks.

All the things Blazej say apply, but there's also a mention of actors who are in front of the ugly stuff you want to get rid of. From the sound of it, there will be lots of roto work involved, so - like Steve says - without seeing (frames of) the actual footage it's not easy to give you a step by step walkthrough.

Thanks for the advice.

The shots are pretty static, all on tripod except there is minor panning. Some shots on a dolly moving slowly. At most two people in the shots. Probably 1.5 minutes in total.

Rotoscoping for sure, I don't know how well Fusion does this? I found it was quite easy on AE.


Jules

Fusion does this about as well as other programs. It mostly depends on the artist how well the result turns out. You can send me a link to (some of) the footage privately, so I could give you some better informed suggestions.

Panning can become sort of a problem. If the center of rotation is not in the nodal point of the camera then even panning will introduce a slight parallax. If you are lucky you might get away with simple 2D masks & treat everything like a big traveling matte. Regardless, just to quickly answer what I can see is probably your question: Yes Fusion can be perfectly used for jobs like this. It was actually made for this

Thanks everyone for the advise.

Thanks Sander for the offer to look at the material. I've time this evening to put a rough edit together for the rushes and I'll see what exactly there is.

From memory we did use tracks on a couple of shots as well. Mostly, 90% of the rotoscoping would be just the top half of their heads as when the actors were sitting down the window frames started quite high luckily.

Jules