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Topic: Caustics: Inverse Square Falloff 111
posted by GREG3D
archived on 3.6.2002
If you use a MAX light, with VRAY shadows, and crank up the Multiplier, you can UNCHECK (in the MAX light general parameters), the Affect Diffuse and Affect Specular checkboxes and the photon map will still be generated and NOT illuminate the scene!
This is great, so now you can light your scene the way you want, then duplicate the lights you want to generate caustics, increase the multiplier, and NOT have them affect the scene.
Follow-ups
Comment: you can also avoid using high multipliers by setting the Inverse Square Start Distance to a level below your ground.
Q: Right, but with that approach you are not using the inverse square falloff...so why bother using it to begin with? I'm assuming that the falloff of the photons doesn't start to diminish until they are under the ground plane either, resulting in uniformly bright caustic patterns.
Personally, I always prefer inverse square lights, they add an extra level of realism to the lighting. And after all, isn't that why we are using Vray for? :)
A: I needed a fix for an OUTDOOR scene.
I didn't want any falloff on my Sunlight.
I was trying to use refractions on shallow water and this trick made it possible.
The caustics in that scene were setup to be minimal. I just wanted it to work and not have to resetup a complex lighting situation.
Comment: You may have misunderstood...I meant, since you are negating the falloff aspect, why use inverse square falloff at all, thats what I meant by that Mike. Of course, it makes no difference either way since the light doesn't illuminate anything.
As for the technique you outlined...thank you, every tip and trick is always appreciated and always useful.
Q: Sorry if I came off the wrong way, but I underdstood inverse falloff had to be on for caustics to work. Inverse or Inverse Square. has that changed?
Comment: I got that impression from reading the help file also, but It's not the case. I think I misinterpretted the passage that suggests setting inverse square and a falloff starting at 1, in order to simulate real world light falloff.
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