A Shader that maps to the Alpha Channel?

TheMysteryIsThePoint

So I have an idea, and I'd like to solicit some better informed opinions:

My main project has a lead protagonist who is a Drow Priestess. As such, she is cruel, violent, and volatile, but the arc of the story is about her redemption.

I thought it would be funny to also produce a meta project where she is vacationing in real world Los Angeles, and being interviewed by me seaside in Venice Beach, as if she were any other up-and-coming actress, playing the role of a Drow Priestess. The rub is that she's not an actress, she really is a Drow Priestess experiencing Los Angeles. Pure fish-out-of-water trope... I can think of a million bits like she originally gated in to Seattle, but didn't like it because the weather was too much like back home and she would of course be wearing sunglasses and an "I Heart LA" t-shirt. Maybe you have to be a D&D player, I dunno.

Anyway, I'm thinking about the technical aspects of doing so, mixing real world footage with the render. What first comes to my inexperienced mind is to set up the lighting, camera position, and camera setting to match the real world setting. I would go to Venice Beach tomorrow and measure out a spot and model it in Hexagon.

If that isn't an unworkable idea from the git go, I see the need for, say, the part of the table and bench she would be sitting at to map to the alpha channel where it occludes her, so that I can simply compose the rendered images on top of the real ones. This is fundamentally different from transparency, where the pixels would map to the rendered object behind the rendered transparent one, which is not what is needed. Maybe a green-screen object or something?

Or is this sort of thing done in post processing, or am I TOTALLY approaching this incorrectly?

Richard Haseltine

That does sound like post processing, though in 3Delight you could use pwCatch to apply the background (in thsi case your photo) to foreground objects (the table). I think you might be able to do something like this in the Iray Canvasses, but I'm not quite sure how to set it up - and I think it would end up with a separate masking image which you would load into a mask in your editor (perhaps an ItemID canvas).

TheMysteryIsThePoint

Yes, I do think Iray Canvasses are what is necessary, if I am understanding it correctly.

Thank you.

WendyLuvsCatz

Hitfilm Express is free for a facebook or Twitter share and has keying and masking among other features and you can render images, otherwise any image editing softwares as long as you have transparency or a solid keyable/selectable and eraseable colour in your render on parts you want to swap out.