I would like to drive a light intensity with the lightness of another layer.
Think about one layer with a "lightning fx" & a second one with clouds in 3D & a light illuminating the clouds layer. So any time you get a lightning strike, the light illuminate automaticly the clouds layer.
I've tried with an expression, linking the light intensity to the "level fx" of the lighting layer (RGB or ALPHA), but it doesn't works !
Any idea ?
Do I need a special plugin to be able to analyse the lightness of the lighting layer ?
Thanks in advance for your help.