Material Switch/Blend based on specific light recieved

[ricoholmes]

Hi all,
Is there a method for Switching or blending a material based on how much light it receives from a specific light ?

eg:
Rock texture that switches to mossy rock in shadowed areas, but only from sunlight.
Motes that switch to glowing lightMtl when caught only in moonlight
Melting glowing metal when caught in a ray beam
etc.

I'm sure there's an obvious way (preferably blend material route) but it's got me stumped.


I could do it in post using multiple renders and LightSelect of course, but it requires heavy imagination as well as multiple renders. A way of doing it directly in shader form would be superduper especially in lookdev.

[vlado]

Not that I'm aware of, for the moment.

Best regards,
Vlado

[ricoholmes]

Damn, but thank you for letting me know. It's something I've wanted and tried many times in the past. At least I can stop banging my head against the wall.

Righto.. I'm off to the wishlist forum now

[Dan Andersen]

Perhaps you could use a surfaceLuminance node, piped through a remapValue, to isolate the surfaces receiving the most light and use that as your blend material mask. It's not perfect but I seem to remember having used that setup for light/shadow based shading in the past.

/Dan

[vlado]

The surface luminance considers all lights though.

Best regards,
Vlado

[Dan Andersen]

It does, but in some cases (perhaps also the ones listed by ricoholmes) the difference in intensity between the key light and other lights in the scene will be great enough to effectively isolate the primary light source.

[vlado]

Some of those things you could probably also do with some kind of a directional occlusion texture...

Best regards,
Vlado

[Dan Andersen]

Sounds interesting - how could this be set up in VRay?

Some of those things you could probably also do with some kind of a directional occlusion texture...

Best regards,
Vlado

[ricoholmes]

Much appreciated input
The surfaceLuminance route has worked for a few things in the past, but as Vlado says it has a habit of clashing awkwardly and often unpredictably with other lights. in the end it's easier to isolate via lightSelect elements.

Now, having said that. A directional occlusion texture sounds like a very plausible route. In words at least. I wouldn't have the slightest clue how to set that up.