Blender Background Subtraction: Pulling a nice matte.

Support Compositing and Post Processing
1

Hi,

Can anyone help me on this one? I have two source files, one is a video and one is a picture of the exact same scene, minus the subject. Like the pics below: http://springconcert07.googlepages.com/img1.jpg

and:

http://springconcert07.googlepages.com/img2.jpg

Is it possible to take the image of the background and subtract it from the video to be left with either a final image or a matte that can be used to alpha map the background out? I have tried the difference and subtraction methods, and they won’t produce what I can see to be a usable matte. Maybe I am doing something wrong. Hope someone can help. I have attached my results with the difference and subtraction methods, and the node setup I am using (just to get the matte, I don’t have the nodes set up to add in a new background yet)

Thanks,
Sciman

Attachments

difference.jpg800×600 74.6 KB

differencenodes.jpg1024×770 67.3 KB

subtract.jpg800×600 41.4 KB

subtractnodes.jpg1024×770 66.4 KB

2

I have given it a try too
with basically the same setup.

but it seems that in some areas you and your background seem to be surprisingly “equal”.
so there´s no real answer from me. sorry.

http://bildupload.sro.at/a/thumbs/Nodes_fail_1.jpg

3

An interesting idea. I guess if it would work, though, people wouldn’t still be spending money on green screens.