Light or shadow Detection shader

tuxmask75 · Dec 2012

Hi guys,
I'm wondering if it is possible for a shader to know what vertex or polygons are being lit or in shadow somehow.

I'm wanting to take that data and make a sort of "If statement" or mask which will be used to change between 2 textures depending on if its receiving direct light or in shadow.

ambershee · Dec 2012

Shaders always know, because they are responsible for how surfaces handle lighting...

Sounds like you want to lerp between two textures based on the dot product of the light and camera vectors.

tuxmask75 · Dec 2012

Actually yes, exactly what im wanting to do.

tuxmask75 · Dec 2012

Here is what i've got so far. Thanks!
Looking for a way to make it so that its a clamped effect so that there is no in between blending,

ambershee · Dec 2012

To clamp it, you can fiddle with the values that you get from the dot product and handle them like you would any other scalar. They should generally be in the range of 0-1.

LoTekK · Dec 2012

Shouldn't you be getting the dot product of the Light Vector and the Surface Normal? In your node network, you're dotting Camera Vector with... itself. Which will net you 1 (I assume it feeds into the subsequent dot node as [1,1,1], which is... wrong).

Also, mind that this will still return lit even if there's a cast shadow over the surface, since it only checks for light direction relationship.

As for clamping the results to on/off, you could use an If node.

eg:

tuxmask75 · Dec 2012

Hmmm,,, could not obtain the same results.
Also how are you setting the connecting lines to be strait ?!

Light or shadow Detection shader

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