physically correct subsurface scattering basics
Posted 22 August 2012 - 02:25 PM
I realize it would be similar to diffuse reflection, like a collision of a ray would produce many rays - and maybe some reversed randomized path tracing method from visible side to the light might be a better implementtion - which would give a correct result after averaging some high enough sample count.
I dont even know how to start, I realize it definitely has a vectoral property, as it has before its even glanced off the surface to begin with. First thing I worked out that draw me to the conclusion I know nothing, was what do I even do to begin with? Just taking the diffuse reflectance and starting with that as a factor sounds completely wrong, Im guessing colliding to begin with and colliding ever after could be the exact same method, its got to be some dependancy of how far apart you make your collisions, like youd think absorption and angle change would have to do with how far you make your collisions apart as an optimization.
Id like it detailed enough a method, so you could put non scattering substances inside, or even take into account an uneven medium.
Im thinking possibly it could be simple but there may be some strange words involved.
Anyway, if anyone could help id be very happy... im tired of having basic gi and no scattering to go with it - my lux 3d renderer is never going to happen at this rate.
Posted 22 August 2012 - 03:22 PM
Posted 22 August 2012 - 04:34 PM
Posted 22 August 2012 - 04:40 PM
So the light goes through and gets randomly scattered with a certain probability per unit length. Each time it's scattered it ends up going in a random other direction. Just as there's a BRDF for a surface that describes the probability of getting scattered in different directions, likewise there's a thing called the phase function that describes the probability of scattering in different directions for a volume. The Henyey-Greenstein phase function is a common one. For subsurface I'd imagine you could just use isotropic scattering (all goes in directions equally) as a good approximation though.
Posted 22 August 2012 - 05:47 PM
cheers man *clink*
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