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sparrowhead
01-25-2009, 03:51 PM
I have been trying to get out some renders from XSI, Im rendering out some Passes to comp in the FX Tree.

So I have my diffuse layer, Ambient occlusion layer, then taken a load of channels out my main beauty pass.

My problem is that I have rendered out a object ID layer, now I'm trying to isolate a particular colour and then use this as an Alpha mask. I want to do this to isolate some reflections and make some glossy.

How the Heck do I do this? I've gotten as far as using a colour extract node to isolate the particular colour, now How do I use this colour selection as a mask? I'm guessing its pretty simple just can't get my head around this!

I can do it 5 seconds in After affects, just wanted to figure this out using a node based approach!

Any help will be greatly appreciated.

TIA

Chris

luceric
01-26-2009, 05:22 PM
I would use the keyer.

1) Add the keyer to the FxTree.
2) Connect the FileInput node both green inputs of the Keyer.
3) Double-click on the Keyer node.
4) click a pixel in the Fx Viewer that's the color you want a matte for
5) switch the "Output" parameter of the Keyer, which is located at the top of the Setup Matte pane, to Output: Matte
6) move the little Yellow Square on the "R", "G", "B" sliders towards the Cyan Arrows to remove any spill

if getting the matte is difficult, change the keyer Mode parameter to Mode:HSV. Change the Output back to "Composite" to see the original image and pick another pixel

sparrowhead
01-26-2009, 05:59 PM
Works a treat luceric.

Many Thanks for the help,

Chris

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