Nuke Primatte Node problems

#1

Hi all, I am trying to use the primatte node in nuke and for some reason it’s not letting me select the colour to remove.
I have a very simple flow at the moment. My project settings are set to HD (1920 1080), I have a read node, then a tracker node (with 2 trackers that have translation and rotation turned on - this node is set to stabilize footage)…Then I add the primatte (connecting the bg arrow to the tracker node) and I click the background colour swatch as normal, and then hold ctrl + shift to select the colour on the footage to remove…but it’s not removing anything.
Auto compute doesn’t work either!

Not sure what I’m doing wrong here, I’m relatively new to Nuke, but have used primatte before and have worked with more complex flows than this, not sure whats wrong, most likely something really obvious!

Thx in advance

Arvind!

#2

make sure the little colourbox under “select BG color” has the sampler icon in it, if not, click it so it does.

also, when keying, check if your alpha is adjusting

#3

Thx for reply, the colour picker is selected and the alpha is not adjusting at all, the alpha is just black!

Any other ideas?

Arvind!

#4

Does any1 have any other ideas of why my primatte node is not working???

#5

You have to pipe the tracker node into the FG input, not the BG input of the Primatte node.

The BG input is used to connect to whatever footage you want to show up underneath your newly keyed footage.

I just use that as a temp comp tho, it’s better to just get your matte out of the Primatte node, and then premult, and then use a Merge node to comp over your background(rather than use the BG input). Hope it helps :wink:

#6

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