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Black Glow around Alpha Transparency
show user profile  pkarpenko
Hi, all. I have some glowing objects that I'd like to composite onto other footage, but when I render them out, they have a black glow outline around all semi-transparent regions.

Take a look:

If I load the composite footage as an environment background map in 3d max, the outlines don't appear (they also don't appear if I render with a white background). What's going on?
read 1228 times
11/13/2011 6:00:02 AM (last edit: 11/13/2011 6:00:02 AM)
show user profile  gogodr
I think it may be because of the ambient color being black. try changing it to white or if it doesn't appear when you render with a white background why not just do so and still save it with alpha channel?

Hello there

beautiful ;3

read 1220 times
11/13/2011 6:39:46 AM (last edit: 11/13/2011 6:44:47 AM)
show user profile  pkarpenko
The ambient color has no effect, but whatever the color set as the environment background, the semi-transparent edges have that color glow. For white, it does this:

I need to to just be properly alpha-ed.
read 1215 times
11/13/2011 7:00:55 AM (last edit: 11/13/2011 7:04:03 AM)
show user profile  chillywilson
When doing things like glow effects, BG light bleeds around the objects and can get caught in the alpha.
Try rendering out a separate alpha channel. Also for stuff like that i tend to render out 1/4 more proportional to the output size, I then use a matte choker in AE or equivalent alpha choker, in whatever composting program of choice.

read 1201 times
11/13/2011 7:21:45 AM (last edit: 11/13/2011 7:21:45 AM)
show user profile  mrgrotey
in photoshop you need to go layer menu-->layer matte-->remove black matte (or white), there is probably the same type of command in your program. It removes 99% of the alpha problem.

Also only render on a black or white background when using alphas, whichever is the best for the image

read 1194 times
11/13/2011 9:51:34 AM (last edit: 11/13/2011 9:51:34 AM)
show user profile  pkarpenko
Thanks for your help, guys, but a choker's not really an option because I have lens flare effects as well, which look terrible when choked. Here's the original composite with the black glow I want removed:

and here it is with a choke:

The transparency within the lens flare is completely lost. Perhaps a separate alpha channel will help. What's the easiest way of outputting that from 3D Max and applying it in After Effects? Thanks again.
read 1185 times
11/13/2011 5:06:12 PM (last edit: 11/13/2011 5:06:12 PM)
show user profile  advance-software
umm - why not just blend it on top additively then any black will have no effect anyway.
read 1180 times
11/13/2011 5:17:59 PM (last edit: 11/13/2011 5:19:06 PM)
show user profile  pkarpenko
Beeeecause I .... failed Blending Modes 101? Thanks, that works great!
read 1172 times
11/13/2011 5:40:40 PM (last edit: 11/13/2011 5:40:40 PM)
show user profile  soontekk
remove black matte in ps or use premultiplied alpha in ae

melting ur brainz!
/ FOS4 / FO2 / Blurb / Twitter / Facebook / Vimeo /

read 1165 times
11/13/2011 6:19:06 PM (last edit: 11/13/2011 6:19:38 PM)
show user profile  brazz
that is one huge gun..

ok back to work.

read 1149 times
11/13/2011 8:57:06 PM (last edit: 11/13/2011 8:57:06 PM)
show user profile  pkarpenko
I finished the video test that his was for. I ended up going with a Lighten blend mode. It's not as perfect as the shot looked when I composited the 3D elements onto the footage in 3D Max (by rendering out the sequence as a background), but it's acceptable for this.

Check it out:

read 1125 times
11/16/2011 5:53:27 AM (last edit: 11/16/2011 5:53:35 AM)
show user profile  Loud
This may or may not help here but it wouldn't hurt posting.

I use it all the time when I have alpha issues with Photoshop files.

read 1117 times
11/16/2011 7:31:44 AM (last edit: 11/16/2011 7:35:13 AM)
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