Key out bg and garbage the garbage?

Why is the ancient process of keying out a color background and then garbage matting out the garbage so complicated? I am sure I could accomplish this in about 5 minutes with PP and yet I feel like a complete moron after fumbling around with Fusion for an hour. I got a good key using one of the 300 methods Resolve offers for keying (Delta Keyer), but my articulated garbage matte (polygon in Fusion) meant to eliminate stuff in the frame is just isolating the subject matter and eliminating my key.

What am I missing here?

Can be done in Resolve


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What am I missing here?

At a guess, your Polygon is not going to the Garbage Matte input of the DeltaKeyer, but instead to the blue Effect Mask input. Meaning it's telling the DeltaKeyer "only affect the area shown by this Polygon", which is kind of the opposite of what you want.

The colours of the inputs matter, and it's a common newbie mistake to have connections going to the wrong inputs.

Garbage matte set up wrong:


Garbage matte set up right:


Quick tip: when dragging a connection to a node, hold down Alt then release the mouse button with the connection over the node. It pops up a little menu in which you can choose which input to connect your pipe to:



If that's not your problem, show a screenshot of your node layout.

PS. in case you've not yet seen a good tutorial on keying in Fusion, here's a couple of tutorials using the DeltaKeyer and CleanPlate (which often gives much better results than the DK on its own). First one is beginner friendly, the second intermediate+.

Your quick tip did it for me, thanks!