layering shadows in post

[super gnu]

our client has thrown a massive curveball into our project. we have a number of objects, all of which cast shadows on a plane.

client has asked for all objects on seperate layers so they can move them about for different compositions. we currently have the objects on one layer and the shadows on another, with the plane behind them all.

separating the objects is easy as they dont overlap.

we can also render seperate shadows for each object, however in our current arrangement the shadows intersect with each other, and if client wishes to re position them, they may well intersect in the new arrangement too.

is there a recognised way to combine shadows in post, so they behave correctly? we are going a bit bonkers trying to figure out a reliable method.

[dgruwier]

You probably figured something out, but for future reference the "darken" blending mode or equivalent is probably what you're looking for, works great for blending overlapping shadows.