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Light leaks in intersection of the solids

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Tim Fast
Light leaks in intersection of the solids
on Jul 29, 2011 at 11:11:56 am

Hello,

I have a weird problem. I have two 3D solids intersecting at right angle and a point light behind them. However, the light leaks in the intersection so that I see a vertical narrow chink of light which is of course not desirable. Please see the attached project.

I wonder whether anybody has an idea why it is happening and how I can avoid it. Thank you.


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John Cuevas
Re: Light leaks in intersection of the solids
on Jul 29, 2011 at 1:36:08 pm

Not sure I understand why it's happening, but I changed your "Light behind" to a spot light and the problem went away.

Johnny Cuevas, Editor


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Tim Fast
Re: Light leaks in intersection of the solids
on Jul 29, 2011 at 1:51:57 pm

Thank you for your help Johnny. I can proceed with the project now. :-D Even if I would still like to know why it happens. :-)


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Todd Kopriva
Re: Light leaks in intersection of the solids
on Jul 29, 2011 at 9:46:27 pm

Change the blending mode for the layers to Alpha Add. Here's a not about why from After Effects Help:

"Note: Sometimes, when layers are aligned edge-to-edge, seams can appear between the layers. This is especially an issue with 3D layers that are joined to one another at the edges to build a 3D object. When the edges of a layer are anti-aliased, there's some partial transparency at the edges. When two areas of 50% transparency overlap, the result is not 100% opacity but 75% opacity, because the default operation is multiplication. (50% of the light gets through one layer, and then 50% of the remainder gets through the next layer, so 25% gets through the system.) This is like partial transparency in the real world. But, in some cases, you don't want this default blending. You want the two 50% opacity areas to combine to make a seamless, opaque join. You want the alpha values to be added. In these cases, use the Alpha Add blending mode."

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