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3D reflections of live action footage – need advice ASAP
Hello All,
I have an interesting shot to pull off and I’m not quite sure how to do it. This may be a question for the 3DS Max guys out there, but I was hoping I could handle it in After Effects.
What I have is a shot of 2 news casters leaning against a table, giving a news reel. I need to key them out and replace the table for a nice shiny black marble one (the kind you would find in any big news studio). I told the props girl to put a dummy table in there with some green-screen material on it so that I could key it out. Now for the problem – how do I get the arms of the actors to reflect properly? I assume that they will be leaning forward, adjusting papers, etc. and all of this will need to be represented in the reflections.
I was thinking that maybe I could roto out the arms, invert them and overlay them back on, but this didn’t totally work in the tests I did because of the perspective.
The good news is that the camera is locked off on a tripod, so I won’t have to compensate for any movement.
I have to shoot this tonight, so if anyone has any ideas let me know ASAP!
Thank you very much in advance,
– Spencer
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17 Replies
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Might want to give Andrew Kramer’s tutorial on here a look…
https://library.creativecow.net/articles/kramer_andrew/reflections/video-tutorial
or better yet, try his free plug-in..
https://www.videocopilot.net/tutorials/reflection_plug-in/
Pretty sure it works on alpha channels, so if you dupicate your footage layer and rotoscope out all but what you want to reflect(the arms), the plugin should do it for you, and give you quite a bit of control as well.
Steve Brame
creative illusions Productions -
Thanks Steve, but this only works on layers that are totally flat. For example if the actor leans forward on the table and you are shooting a medium shot from directly in front of him, there is a bit of perspective between his hands and his elbows. If I roto these out and then apply AK’s plug-in to it, it will look as if only his hands touch the table and his arms are floating or something.
Thanks for the suggestion though, maybe there is a way to build on this idea. I was thinking that if I did some sort of 3D distort on the arm I could then rotate it down in 3D and get a reflection. But that would involve camera-mapping the footage onto a 3D card that is placed at about the same position as his arm, then applying the plug-in to it and placing it back into the comp – something that would be too complicated for the time involved.
– Spencer
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Then I think you were on the right track initially…dupe the footage layer, invert, then mask out what you don’t need with heavy feathering for falloff. You should be able to really adjust for the perspective issue with Corner Pin or similar.
Steve Brame
creative illusions Productions -
Dear All,
I figured it out! I thought I’d post this, because it is purely genius! (I can’t take all of the credit, a gaffer gave me the idea.)
All I did was stick 3 plates of glass on the top of the table side-by-side (repurposed from some picture frames in the studio), that way the actors can do whatever they want and the glass will pick it up in the reflections. Then when I key it, I’ll roto the glass out and key it separately as a reflection and composite this back onto the CG table-top!
– Spencer
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Post a sample here when it’s done if you can. That sounds very interesting.
Steve Brame
creative illusions Productions -
I’m sorry, I don’t think I can (due to legal). It’s pretty simple to set up though, just make sure that your glass is only reflecting green and the actors (we had a 8-10 foot high screen 6 feet behind them).
– Spencer
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I did a test run before we went ahead and shot it. The reflections were extremely bright – not like a car window or something – due to the low angle of the camera (about eye level). This makes it pretty easy for me to key.
In the end I plan to roto out the piece of glass (including the reflections, minus the hands) and then key this separately. This way I can have a finer matte, and some more control over how the reflections look. Then I can dim them, blur them, etc.
So far I have seen 2 problems. 1: it is a little tricky to key with the shadows and such also being cast on the table. 2: because this is a little more sensitive there was a little more grain and whatnot in the test I did. But this should all be handleable.
– Spencer
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I’ll be posting a few frames in the next hour or so! I think it turned out well, the only problem is that there is quite a bit of spill in the reflections, but I just roto’d an adjustment layer and manually corrected that.
– Spencer
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Allright, here is the shot with a little breakdown! I got okay to post it, as long as you can’t see the actor’s faces – so I thought it would be all too fitting to do a mosaic.
– Spencer
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sorry, forgot to put the link up!
https://f1.creativecow.net/1548/reflections-key-final-shot?uploaded=file
– Spencer
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