Hi,

I have a nice grid-like image I want to use to create an alpha (If alpha is what I need!) to use as a transparency jpg for use in rendering - so I can see under the floor! (through the grid)

Okay, I've selected what I want to use, saved the selection, created an alpha channel, only....

Is this the right way to do it?  is the selection the right way instead? (i.e. quickest) 

I have a totally different image for the floor already, I was planning on layering this image with that floor to give it a grid-like appearance - and the transparency would just punch the holes out to reveal what's beneath the floor.

The transparency needs to be black and white, that I do know.

I'm sure I must have done this before but my mind's a blank.

 

I just realised that I didn't make clear that I have already created an alpha channel (I called it "Matting") and I have saved selections of the holes and the inverse of the holes...

I'm just not sure how to actually get a jpg that looks like the black N white alpha channel, top left of the posted image.

That's what I need to do in the simplest manner - only how???

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