Blending real shadows with cg shadows


Hi everyone,

I’m currently working on my demoreel, but I came across a problem, that I couldn’t find a solution for. I have this tracked video sequence: footage
I plan to put a chainsaw on top of the table, but the cast shadows of the chainsaw would overlap with the real shadows on the wall behind the table, resulting in a doubled shadow.
I’ve already found this on the web: link
The problem is, that he uses a fixed perspective with a slight camera tilt. This allows him to use one big image, stitched together in Photoshop, that shows a complete shadowed backplate ( link ). here is a link to the complete video with breakdowns: video+breakdowns However, this won’t work for me, because my camera moves around the scene and I can’t just build one large shadowed backplate.
The other thing I found is this thread: link . I played around with the files he provided and tried to apply his workflow to my footage, but to be honest, I didn’t fully understood this method and the attached images in Per-Anders post don’t really look as good as I was hoping for (lot’s of artifacts in the shadows). Also, it’s a still image and not a sequence.

Btw, I work with nuke, but I’would be thankful for any answers, even if it’s for a different software. You can also see the first part of my demoreel here: reel WIP . But I will propably post this again in the WIP/critiques section.

Thank’s for any info/help on this!


No ideas ? anyone ? well, I’ll have to use a mask then… Not sure if this will work out


You could probably crank the contrast up on a plate of this, garbage mask, and use a luma key and blur it a little, and use it as a mask, instead of doing it by hand.


Thank’s Ephisus, and sorry for the late response! I managed to solve the problem with the keylight-keyer in nuke, but your answer has sent me in the right direction. (I had no clue about keying before this project…)
Here is a link to the final video (it comes right behind the Aston Martin part):


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