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Question by PJisAnarchist · Mar 21, 2015 at 01:27 AM · lighttransparencyshadowalphamask

I need my alpha to show only where it is not lit.

Hi all!

I'm struggling on this one! I have a map with an alpha channel, I display it thru an Transparent shader, but I need it to be fully transparent everywhere the light hit the object. This way, I'll see my map, with it's transparence, but only on the shadowy side of my object.

I believe I must substract the lighting value in the alpha, but I can't achieve it! Any help guys?...

PJ

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avatar image siaran · Mar 21, 2015 at 02:32 PM 0
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I think you'll have to write your own shader for this.

Here is some stuff on how to do custom lighting in shaders: http://docs.unity3d.com/$$anonymous$$anual/SL-SurfaceShaderLightingExamples.html

So you'll have to write something that does something with the alpha value depending on light I guess. Yea, that's kind of vague, but I can't really help much more.

Subtracting the lighting value in the alpha does sound about right for what you want to do I think. If you have a custom shader you can post it and maybe someone (probably not me, I'm not very good at them) can help you further with it.

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Answer by PJisAnarchist · Mar 21, 2015 at 02:40 PM

Yeah, thanks. I just solved it an hour ago with:

1 - dot (s.Normal, lightDir);

But it didnt helped me much, and I discovered a bug. I have an alpha'd shader on a second object over a first one, and if the second object is a plane, I cant see thru the opaque areas, while if is a sphere, I can. It makes no sense, I may bug report that.

Anyway, thx Siaran for the kind answer. PJ

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