Alpha Channel Outlines

#1

I recently started doing a lot of live-action/CG mixes, I render my 3D stuff out to TGA with alpha channels. I then comp it all together in After Effects.

Problem is when I do this I get nasty little black outlines surrounding my objects like in the image below.

The vase on the left was rendered to TGA/wAlpha (256 passes even!). The vase on the right was rendered with blue background inside AM. It doesnt have the outline.

Has anyone else run into this problem and has a workaround/fix? When compositing a light object into a lightly colored scene it kills any chance I have of photorealism.

It also appears if I use v12’s .exr export :frowning:

#2

My first guess is to check the method the AE is using to interpret the Alpha channel when you import it. I haven’t looked at AE in many many years, but I recall on import you had to tell it how to use the Alpha, straight, premultiplied etc. Try importing the same image in multiple times, using all the available options, and see what works out best. I never had any problems importing alpha’s into AE, so I think the above should provide your solution.

#3

Sonnuva $#$()#%$#$&@#(&$%!

For years I had gotten into the habit of telling AE to use “Straight” interpretation because whenever I’d hit ‘Guess’ that’s what it would choose. I’d get the same results when I import a TGA into AM as a rotoscope and render it out so I figured it was a AM render issue.

It’s working correctly now. Thanks very much man, I appreciate your help :slight_smile:

#4

Oh man, thanks for that tip Mike, I had been doing the same thing as Matthew and this totally sorted out a few issues I was having. Yeah!

#5

Wow!

I am glad that I wasn’t just blowing smoke. Like I said, it has been years since I touched AE, and I am glad that I still remember things correctly.

I suppose I should check with my students and see if any of them are having this problem as well.

:buttrock:

#6

i had the problem too. you have to set the camara background color to black and render with alpha. in AE you have to interpret the image with black color.

#7

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