How to have a shader that is reactive to lights?

[B037973a]

For Maya / Vray.

I’m trying to create a reactive material, that ‘comes on’ when it’s in the dark.

This video shows a good example, but is using a different render engine: https://youtu.be/EVtj1FV5vz0?t=1391

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I have a model of an earth, with a light which illuminates half of it (the Sun). I want to have a texture (night city lights) to be visible when the direct light isn’t hitting it (in the shadow), Is this possible? I created a version ages ago in MentalRay using ramp shaders with a gamma correction, but the same nodes don’t seem to work in the same way in VRay.

Any help / advice would be appreciated.

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One method I had tried exploring is by using a VRay Light Material, with the texture applied to it, and add a regular ramp node (not shader) but I’m unsure if its possible to track the rotation to the direction of light?

[super gnu]

im not sure in maya but in max you can use a falloff map set to light/dark.. maybe there is a maya equivalent

[B037973a]

im not sure in maya but in max you can use a falloff map set to light/dark.. maybe there is a maya equivalent

You legend! I've not used this node before, it gives great results for what i'm trying to achieve.

For others trying it: link the position of a light source into the 'Explicit direction' of the VRayFalloff (I used a VRayLightRectshape). Then you only need to link the VRayFalloff into the diffuse of your material.

Thanks again super gnu.

[super gnu]

great news. your method is actually a better variant of what i was suggesting, you have far more control. falloff set to light/dark in max is based on scene illumination levels, not direction to a node. however im glad i pointed you at the right map at least , i might use your method next time

[SonyBoy]

I think you could probably also use a Maya surface luminance node to do this, which is probably more accurate as what you are currently doing is kind of a hack based on normals.

[Karol.Osinski]

Agree, I would also try with a surface luminance, makes much more sense.