I have been following treads regarding the subject for a while and

I have have worked for a a week or so to implement the BSSRDF

algorithm in renderman shading language. I have actually written and

compiled a shader that simulate one layer of skin but it's not giving

any interesting result. It's actually kind of wacky. So I went through

the paper one more time and realized that may be some of the

assumptions

that I made weren't correct. I would like to know if there is

someone out there that can kindly verify my theories.

To calculate the diffuse term of the BSSRDF I'm generating a bunch of

point in a plane around P. I'm not compensating for any curvature

cause

reading the paper seemed to me that the all theory olds together

because

we assume that we are dealing with a flat surface. When I have a new

P I compute equation (4) of the paper and than I use a Monte Carlo

method to approximate the diffuse factor of the BSSRDF function on the

original point P.

I understand that to compute the diffuse light I have to use a dipole

method, but even if I create a light under the surface, what is his

intensity? The intensity of the original light shining at that point?

And even if this is the case, where I have to put it? Equation (4)

doesn't have any light! What is "alpha one" in equation (4) of the

paper? I didn't find any explanation so I assumed that was the reduced

albedo coef ( Reduced scatering/absorption coef).

To calculate the single scattering I calculate the transmitted ray T

at

the point Xi ( one of my generated points) where the light enter in

the surface . Then, knowing the

thickness of the layer I calculate the lent of T traveling inside the

layer and from there I create a new vector from Xo, where the light

exit

( my original P) to the intersection point of the T vector and the end

of the layer. this new vector is going to became my outgoing

refracted ray where I sample the single scattering term. Does it make

sense?

Sorry if all this is terribly wrong or stupid, any help is greatly

appreciated.

Mars