View Full Version : Real Lens AA filters don't effect alpha??

09-19-2008, 04:19 PM
I was experimenting with the gaussian reconstruction filter to match the softness of background footage I'm comping the LW rendering with, but once in after effects I was getting all kinds of halo because it seems while the color rendering is soft, the alpha is still hard. I just experimented, and checking the old "soft filter" option effects both like you'd think, which is I guess what I'll use for now even though I'm not a huge fan of it. Is this lightwave being lame, or am I doing it wrong?


09-19-2008, 05:05 PM
I believe that is correct behavior that you've described. Typically "effects" would be done in AE or the like, and since you are compositing it in AE I would look there. You're able to have more control without having to re-render.

09-22-2008, 05:10 PM
Yeah I guess it seems strange to me that the new AA modes wouldn't affect alpha, that limits their usefulness pretty heavily. The reason I was trying to do it in LW is so that the alpha would be correct with whatever blurring I do, whereas if you blur one or both channels in after effects you'll get halo-ing any way you do it since it only has so much color information to work with from the LW renderings.

09-22-2008, 05:32 PM
I don't know if this is your problem, but when I use frames rendered in Lighwave in AfterFX, I go to Interpret Footage (Ctrl-F) and use premultiplied - matted with color, and choose the color I used in Lightwave as background, and the halo goes away.

Captain Obvious
09-22-2008, 07:14 PM
That's a bug. The pixel filter SHOULD affect the alpha as well.

Also, as ivanze suggest, look into whether you're properly unpremultiplied or not.

09-23-2008, 10:52 AM
Aha it takes captain obvious to get my point :thumbsup: Using straight alpha setting from LW, I shouldn't need to premultiply or do anything in AFX. And I'm not actually getting any haloing in AFX--it's just apparent that when I tried soft gaussian filtering that the alpha was still sharp, which didn't result in fringing, it just looks odd.

Captain Obvious
09-23-2008, 03:42 PM
Well, yeah, that'd be a bug then. Report it!