Outline around cloud alfa.

[BlackScvale]

Hi guys, does anyone know why I have this strange outline around my clouds?

[Oshyan]

What exactly is the image with red in it? A composite in another program? It may be relevant to know that TG's alpha is 'spectral', i.e. it is different in the red, green, and blue channels, respecting the appropriate atmosphere scattering properties.

- Oshyan

[BlackScvale]

Hi Oshyan, sorry for not being clear. Yes the image on the red it a comp in After Effects. I have attached a screen shot of that. I also attached the cloud, atmosphere layer. Currently I have to "clip" the clouds to get rid of the outline. This removes a large amount of cloud detail and make the clouds look blurred. I am very interested to know how to get rid of this.
Cheers

[fleetwood]

The atmosphere settings you are using have quite a few non-default settings such as big changes to the haze colors, sky density color and very high blue sky glow amount.
I would suggest copying and connecting a default atmosphere and seeing if you still have the outlines using the defaults. Then change only one atmosphere parameter at a time as you test and compare results.
Changing multiple settings makes it very hard to find the culprit.

[Matt]

I can see two possibilities here.

1) Premultiplied alpha versus "straight" alpha. The images from Terragen are premultiplied by alpha. If you comp assuming "straight alpha", then it won't look right at the edges.

2) It looks like it could be a difference in gamma. It's best to comp in linear colour space. After Effects tends not to do this by default, at least in my experience. Try to get After Effects to comp in linear colour space. If that's not possible, you might need to adjust the gamma of the alpha channel, or change the colour space settings where the alpha file is read into After Effects.

Matt