using Vray material ID causes edge artifacts in Nuke?

[tinuz]

or maybe I should stick to 3D ..

maybe I'm in the wrong forum for this,
but please have a look at the image below:

I am trying to colorcorrect the match-head for which I have rendered an materialID channel in an multichannel exr

but I just can't get rid of the edge that isn't being colorcorrected..
I have tried:
-RAW input on file read
-colorspace on linear and srgb, in every case I get the edges

can someone see what I am doing wrong here?

from top to bottom:
- rgb
- alpha
- material ID, red channel is used
- comped result



or this link for bigger image:
http://tinuz.uncinc.nl/vray/Screen%2...36.57%20PM.png

[pg1]

use multimatte element instead of material id it is correctly anti aliased

[tinuz]

aah ok, thought I was going nuts...
thanks!

[vlado]

Hm, in this case it will be exactly the same. The material ID in Maya is a color channel and is properly antialiased.

What operations are you doing with the elements (it is not quite clear from the image)?

Best regards,
Vlado

[tinuz]

yeah I noticed no difference..

i made a small nuke script for anyone who has nuke:
http://tinuz.uncinc.nl/vray/vray-nuke-forum.zip

please forgive me if this turns out to be a stupid mistake since I'm a beginner at comping

thank you for all your help so far

[MatthewRF]

anyone have any luck with this? i've had the same issues.

[pechart]

Could you also post the maya scene?

[instinct]

Unpremult your mask channel by the alpha.

Regards,
Thorsten

[tinuz]

Unpremult your mask channel by the alpha.

Regards,
Thorsten

that works! thanks,
but it only works if I separate the mask channel with a shuffle node

the option to do this inside the colorcorrect node (checkbox "(un)premult by alpha") doesn't work..

well anyway it's not vray..

[instinct]

You can do that with an unpremult node without shuffling:

Simply change the "divide" knob from rgb to your mask layer. This is a different option than the one in the color correct node.
The one in the CC node divides the RGB by the Alpha (or other channel selected), not the mask.

Regards,
Thorsten

[tinuz]

ah ok, that's clear, thanks again!