Compositing node
Alpha From Luma
Builds a new alpha channel from the picture's own brightness, so a black background becomes see-through with nothing to key against. Invert flips which end is solid, for a white-on-black source.
What it does
Alpha From Luma is a compositing node: it layers, masks and routes pictures. It takes picture in and gives picture out.
Try it
Run fire or smoke footage through it to lift the flames off their black backdrop.
Inputs and outputs
Inputs
- picture input
Outputs
- picture out
Example patch
This patch wires Alpha From Luma to what it needs and shows the result. Download it, then use File, Open in Infinite, or read it here: it is plain text.
infinite-patch 1
rev 2
# Alpha From Luma: a starting patch for the Alpha From Luma node
node 1 Compositing alpha from luma
id node
pos 520 300
end
node 2 Source Ramp
id in0
pos 0 300
end
node 3 Utility Output
id out
pos 1080 300
end
cable node 0 in0
cable out 0 node