Go into Action with the same source as both front and matte in three layers. Back is black or off.
The RED layer gets CC’ed so that gain for G and B are 0
GREEN … cc’ed so that R and B gain are 0
BLUE … cc’ed so that R and G gain are 0
All three image’s surface are in ADD mode, transparency = 100%
(or search tips archive for additive tip)
Now using these axises you can “fly” all three sources, or simply recombine them.
This works on all versions of flame* and inferno*.
Submitter: Henry Birdseye