objectid pass and nMask

Hello we are trying to get a clean mask for color correction with colored object idpass and nMask but are having some issues.
Following the nMask macro for fusion guidelines I've outputted a double size render (from 3delight) , 8 bit and non anti-aliased ( i was advised by the 3delight forum that a 1*1 pixel samples, box filter) would give that result.

you can see that its not working correctly


If anybody has any ideas that would be great

i've decided to go down another route with regular masks

separate masks are usually the best solution... but looking at your image above... it seems like your object ID pass has suffered from compression artifacts! You haven't saved it as a jpeg file by change?

ok i followed what the nMask guide which was jpeg - but your right a .tiff is giving better results
but there is still what looks like a one pixel around the edge and there isnt full coverage of the color correction, but i suppose if the beauty pass is a antiliased pass and the idpass is a unantiliased thats always going to be the case?
http://www.steakunderwater.com/wesuckle ... 118fded6bc


yellow edge showing on cylinder, no full coverage of color correction
beauty pass 32 bit exr, idpass 8 bit tif 1*1 pixel samples pixel filter box

Away from that technique we've worked out how to output seperate masks for each object or shader from 3delight (they are outputted as named aovs) which are giving clean results
I would appreciate any ideas on organising/picking them quickly in fusion. Without having to spend time digging around. I've asked around and there doesnt seem to be as quick a way of picking which mask (as the color picker in the nMask).

Even if you have separate masks in AOVs you need to take care of alphadivide/multiply to get full mask coverage. If you're color-correcting an object you're probably using pre-divide/post-multiply on the tool. But if you're masking that with a rendered mask the mask needs to be divided by the object's alpha channel as well.

Granted, that error is minuscule... but it's something to keep in mind if you're using those anti-aliased masks to cut out objects for example.