Wow, I can't actually believe I'm having to ask a question for such a mind-numbingly simple task everywhere else I've tried it.
This is in actual Boris FX, with Sony Vegas.
In Vegas, I have a clip that is a person moving in front of a green screen, and below that a background plate. I want the person to appear transparent, and just displacing the background plate.
It seems impossible (or remarkably unintuitive at least) to have the actual video that the effect is applied to not be included in the output.
I have the Chroma Key set up, and one would think dropping it into the Mask part of the displacement map would be what I want, but no. The entire layer video still comes through totally un-masked. Like Mask means nothing. No other combinations of anything I've tried seems to work at all. I can get combinations that LOOK like they're only displacing the person part (ie the non-green stuff), but unfortunately the underlying pixels they use are from the original green screen layer, all alpha information is completely disregarded.
Any help or pointers to help me understand what basic principles I'm missing would be greatly appreciated. The plug-in help/docs are not of much use, they elude to what I want, but keep it real simple by having the 'V1' thing be the item that is being displaced, where I need to have 'V1' only be the displacing mask.
I had high hopes for BorisFX and many plans, but to be so stumped on virtually the first non basic thing I've tried (and it is still kinda basic) is quite disappointing.
It's actually fairly easy to achieve the effect that you have in mind using BorisFX. Here's how:
• start with the footage to key
• add the chroma key filter directly to the clip and generate the desired key
• you should now have a single track with the keyed person over transparent background
• deselect the track and add the displacement map filter to the timeline
• twirl down the displacement map filter controls to show the map track
• drag the keyed clip onto the map track so that it nested
• deselect the displacement filter track and add the background track to the timeline
• drag the displacement map filter track onto the background track so that it nested
• you should now see that the background image is showing a fluid-like displacement of the keyed image
Thanks Peter, I did finally end up at that. I had not wanted to have to have a clip referenced separately in BorisFX though. I had wanted to have the background come from the Vegas timeline. And that trying to stick to that thinking kinda tripped me up.