Whilst on the Nextgen Apprenticeship we have learnt how to remove a green screen using a primary matte build. We first started by trying out different ways to remove a green screen like the primatte node or a keymix.
For this task we used a mix of expressions, primatte and grading to get our desired outcome. Our plate was a still frame of a woman sitting in her car facing the camera so we didn't have to worry about any movement.
The plate was connected to a denoise and which then onto the primary matte build you can see below in the green box. The expression is what helps give a soft edge when removing the background before replacing it so there's no hard edges and it helps give a seamless blend. The first grade was to help separate and bring forward the foreground from background in the alpha channel, then inverted due to Nuke removing the black part of the alpha channel. The white constant above the keymix was mostly just to show everyone what some artists do where they prefer to work in smaller sections on a blank slate with the roto just circling the left part of the woman's head.
Using the primatte to get rid of the background and once again using the grade (which should be on) to bring more foreground forward and trying to stop any green reflection from eating into it. I used the dilate or erode node to eat into the foreground to give it a stronger core and then blur. This is all connected to the IR plate on the next slide by a copy alpha where I just have a grade and a keylight. Without the keylight you should have a green border around the foreground so that node just clears it up.
Lastly the background is transformed and cropped to fit in better with the plate, the grades are from an example of what order you would put them in should you need them there.s only some changes to the white point and black point node to match the grading of the foreground.
This was the final out come of the script, as you can see on the right hand side of the car the edges are a bit translucent but it can be fixed with a dilate which we did mess around with in other versions of this script which you can see below. The edges are more defined but the seat belt has been cut off and there's some of the background eating in. With a bit of trial and error it can be fixed.
Overall with this being my first time removing a green screen using this method I am proud of how it turned out, I would like to look into this method more and practice with it for future projects.
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