I love how light intensity can be cranked up past 1 and actually bleach out texture.
But the value is clamped up to 8 and down to 0.
Past 8 would be useful in cases of nuke blast for instance and negative values are very useful for simulating AO at the entrance of a cave (and avoid using shadows).
Wouldn’t a projector work for you?
Negative lighting isn’t a simple thing, but you can take a look here if you want to try your own shaders.
–Eric
I just added a ramp in the FallOff of a Projectors and it works magic! Thanks Daniel.
I’m not up to the task of making my own shaders yet -
The value is clamped to 8 so that light intensity is supported on Radeon 8500-9250 series hardware (where shader constants are in -8…+8 range).
Negative light is not easy, as Unity’s lighting is built on the notion of light being “additive”. With some custom shaders it can be faked.
Dammit, this is the second time I’ve seen a broken forum link about this subject. Doesn’t help that the whole post is 7 years old.
Vert lighting makes negative lighting reasonably trivial if you’re interested in going that route?
Funny how 7 years later the values are still clamped to 8 
Maybe it’s time to lose some of that baggage?
Revive Topic
I’m looking for a shader which can do this, anyone got a hint?