Blackmagic Forum

I'm applying the 3D Keyer on the color page.

On some clips it works. On other clips, even from the same source, it does not work.

Nothing happens when selecting the green screen.


When Despill is selected, the green screen goes gray.


No alpha channel is created.

Any help? I've tried everything.

You have to add an Alpha Output to the Node Editor.

I've tried that as well. As you can see from this screenshot where it is working - there is no need for the Alpha Output - and it works. I believe it is supposed to function this way.

Scratch that - I just added it and tied the 3D Keyer node directly to the alpha output and it worked!

I still think this is a bug.

Mariano215 wrote:I still think this is a bug.

Working without outputting to the alpha channel would be a bug, not the other way around. If you don't explicitly output an alpha channel you should not magically get one.

wfolta wrote:Working without outputting to the alpha channel would be a bug, not the other way around. If you don't explicitly output an alpha channel you should not magically get one.

Wayne is 100% right. For info on chroma keying, read the section "Introduction to Compositing Using the Alpha Output" in the Resolve 16.2 manual, starting on p. 2886. This has not changed for 17 as far as I know.

It is true that in 17, you can now do a simple chromakey on the Edit page, with slightly different steps involved. I would rather do it on the color page, because I frequently need to create a tracking garbage matte with Power Windows in order to tame the key and get everything optimized and looking reasonable.

I was shocked the first time I saw a training video where someone pulled a key in Color. I've always associated keying with an editor or a VFX program. But it makes total sense to do it in Color: you have a slew of color-selection tools and adjustments, fast and reliable mask tracking, etc. So I'm a convert.