Blackmagic Forum

I am not sure if this is intended behavior or not..

Interesting find with Clip layers on color in Resolve 19.. Regarding Alpha channel ..

Say you have 4 layers enabled.

If you pull a key on layer 1 and output the alpha … it does not automatically patch through layers 2-4.

You need to add a source to layers 2-4, and also an alpha out .. and then patch through each layer to end using a corrector node in the middle..

I made a branch and used a single node to bypass nodes on layer 2… did the same for Layers 3-4.

Pic 1 we can see Santa here with a 3d keyer applied, and the alpha has been patched. However the Green background is not removed, and Grey Ramp background does not show up:



Patching the Alpha through the additional layers using a Source and Alpha output on layers 2-4 will allow the alpha channel to work correctly:



And so on for layers 3-4:

Looks like a nasty oversight. Logically it sorta makes sense but it is by far not the desired behavior by default.
I don't even have any idea how this could be solved in a clean way without breaking established mechanisms. Perhaps an alpha passthrough switch toggle that takes whatever the last alpha output is in any layer.

shebbe wrote:Looks like a nasty oversight. Logically it sorta makes sense but it is by far not the desired behavior by default.
I don't even have any idea how this could be solved in a clean way without breaking established mechanisms. Perhaps an alpha passthrough switch toggle that takes whatever the last alpha output is in any layer.

Yeah. It kinda makes sense to me also. I could see this being potentially useful for some , but at the same time confusing to others… and maybe instead of adding a new source… We get a dedicated Alpha input source..

I would love it if the alpha output would be seen automatically as a (blue) source in the next layer.

It does kind of make sense to pass alpha automatically to following Stacks. (Even if you add a new Stack after the grade begins.)

shebbe wrote:Looks like a nasty oversight. Logically it sorta makes sense but it is by far not the desired behavior by default.
I don't even have any idea how this could be solved in a clean way without breaking established mechanisms. Perhaps an alpha passthrough switch toggle that takes whatever the last alpha output is in any layer.

So as a follow up… this layer patching system feels a little half baked.. We need the ability to create more outputs .. Currently we only get 1 alpha output.. but what if I want to pipe 4 layers into color from fusion… as implemented there is no way to pass them from L1 to L2-4… so you are forced
To comp on L1…. Even though L2-4 allow you to create source inputs .. they don’t do anything as far as I can tell (aside from the alpha). Will keep testing.