View Full Version : comping 3d files in combustion - fringies

03 March 2005, 07:54 AM
Ok outputting some 3d layers from maya and comping them in combustion.
Having used digital fusion in the past, ive normally just rendered out passes for my different lights and comped them one over another using the screen transfer mode.
I do the same thing in combustion and am getting black fringes. I have a feeling its got something to do with premultiplied alphas, but im not too sure. Ive been fiddling with all the different setting and cant seem to get one that looks good...
Does anybody know how to do this? what are the settings other people use?

03 March 2005, 08:09 AM
Ive done a bit of searching around and the solution always seems to be to use the matte controls to shrink the matte. This seems a bit silly to me for a comp out of a 3d program. just to make things clear ive also clicked the premultiplied with button on and off in various combinations.

03 March 2005, 06:21 PM
You can also use an alpha levels keyer and adjust the mids down a bit. That works pretty well for me. But I guess you don't want to tweak anything at all in combustion and get a clean matte out of maya straight away.

I get that effect with or without premultiplied alpha, with all image formats i've used, with every renderer and so on. I got used to it and it's become second nature to apply that keyer to anything out of a 3d app.

03 March 2005, 10:53 PM
Thasnks t.fadrus, Ill try the alpha levels as well. I guess it does work and its looking ok, I just didnt think you should have to do this... oh well..:shrug:

03 March 2005, 10:46 AM
So yesterday I was working with combustion again and stumbled across the premultiplied alpha option. I have "Learn more on premultiplied alpha" on my palms to-do list for a month now, because I never really knew what it was. But remembering this thread I tried it and guess what, all of a sudden the black borders around the cg elements were gone. I have to thank you in return for pointing me at that. The strange thing is, that it's not working for you.

Maybe you can post a small workspace and I can check it out.

CGTalk Moderation
03 March 2005, 10:46 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.