[Dale Paquette]

Thanks, Dale

[Dale Paquette]

Thanks for your thoughts. I have looked at a few other keying packages but since I don’t have them, I’ve not gotten too far. Where I am starting gain some deeper insights is in study of scholarly articles on computer graphics and research papers from several universities. Of course, it’s easy to get bogged down in the math, but there is a lot going on that I suspect will seriously impact our industry one day. I’m especially impressed at some of the progress being made in keying based on depth mattes which will separate an arbitrary subject from an arbitrary background (the holy grail if you will). In its current state, this requires a laser scan along with the photography, but there are some statistical approaches showing promise. In the meanwhile, I am headed towards reverse engineering if you will the Keylight algorithms, at least close enough that I can conceive of variations and alternatives to help the process along when the going gets rough.

I hope others are interested in the details and this thread keeps going.

[Dale Paquette]

Thanks both. I agree completely with your assessment. What I’m actually trying to do is better understand the actual internal math that allows keying, spill suppression, and compositing to work. Steve Wright’s book Digital Compositing for Film and Video does go into some significant detail and suggests that if your keyer of choice (Keylight in my case) runs into a problem there are alternatives if the math is known. I suspect, there is still another level of detail beneath what Steve describes and I suspect I may indeed have to get into the science of image processing to wring out any more.

[Dale Paquette]

Thanks to both. I’m familiar with light wrap and have rolled my own as well as used a script from AE enhancers. I need to think this through though honestly, I’m not sure. I dug through my stack of notes and found the reference in a description of a training program from cmivfx.com under Nuke advanced keying. No details are given at all and they include light wrap as a separate topic.

[Dale Paquette]

Thanks, that was the clue I needed – finally got it working.

[Dale Paquette]

Thanks. Your ideas have lead to a concept I will experiment with once the results of Hurricane Sandy are cleared out of here. The actor will walk along a path and at a specific spot, change to heading to a different destination. A second shot will be of the actor starting in his best estimate of his pose at that spot then walking off oppositely. The second shot will include a green screen behind the actor.

In post, the two plates will be set up with the second shot on top. With its opacity reduced, the two layers will be synchronized in time as closely as possible in terms of position.

Then, the green screen layer will be keyed to yield a decent alpha channel. Layer one will also get the puppet tool applied and animated to distort the second shot to a very close fit to the first shot. The distortion should not be so bad as for the actor to appear distorted and the animation need only be a handful of frames to smoothly remove the distortion. The bottom layer will fill in where the green screen was. Several shots may be needed to get one good one and a field monitor would be very useful.

This would work in reverse as well to bring them back together into one later.

If need be, maybe a dog running past at the critical moment barking as it went would be just enough to draw attention and allow the illusion to unfold unnoticed.

I hope to shoot this one soon and will post.

[Dale Paquette]

Under most circumstances I do use AE for stabilization both using the built-in point tracker and the Mocha planar tracker. The Ps technique suggested by Harrington more closely approximates Mocha. That said, both of these methods have limitations and so I’m experimenting with Ps as an alternative. I have some footage of the sky only with some minor shakes I’d like to use and there is simply nothing there to lock a point tracker onto. Likewise,I’m not having much luck with Mocha. The Ps technique does allow me to isolate the 1 or 2 frames (layers) where the shakes are and manually adjust them. I could also do so in AE.

[Dale Paquette]

I think I’ve answered my own question. While I expected the stabilization process to take some time, it takes a lot of time! 60 frames required nearly an hour. That said, I have never been able to stabilize intentionally shaky handheld footage as well as Ps did regardless of technique.

I now need to explore stabilizing with camera pans and prominent moving subjects in the footage.

[Dale Paquette]

I’m afraid I can’t answer the question, but I have a similar need. When I use the motion tracker for positional stabilization, a keyframe is applied to every frame to mark a change in anchor point location. I would like to export the anchor points in a file of any kind (text is fine) so that I can calculate the average change thus enabling me to position the tracked layer such that the maximum black border around the stabilized footage is the same in +/- X and +/- Y. Thanks

[Dale Paquette]

Thanks. Dale