Skin specular BRDF - some help please

[ofer]

Hi,

I am trying to implement some ideas from the skin rendering article in GPU gems 3. I began with the specular BRDF model.

I implemented it in VOPs, but the results are wierd. I can't get it to work, and I can't find the problem.

I think maybe Im normalizing vectors which I shouldn't. Maybe there are some mistakes in the code listings, I don't know.

If I won't find the problem I'll go to the referenced articles, and check that, but I'll probably won't understand them.

I attached my hip file. Notice the weird issue with the normals. I have to flip them for rendering, but in the viewport I must not flip them.

And also, I implemented the PHBeckmann function in COPs, to generate the lookup texture, the article describes. I don't use the texture in the shader,

but I just wanted to see if I get the same results as the texture in the book, and I do.

So if anyone cares to take a look at that, I will be very grateful.

Thanks.

KSSpec.hipnc

[ofer]

Sorry, I can't upload the geometry file. It says -

"Upload failed. You are not permitted to upload this type of file"

Ill try again later.

[ofer]

I cannot upload geometry files.

I made some progress though. I realized the eye vector is from camera to surface, and that I should negate it when computing products with

other vectors. I also replaced the fresnel approximation with the fresnel VOP (The results are the same).

So now I think it works, but very dark. If I use their value for rho_s (0.18), I see nothing. I set it to at least 1. So maybe I still has a mistake somewhere.

[Jason]

Sorry, I can't upload the geometry file. It says -

"Upload failed. You are not permitted to upload this type of file"

Ill try again later.

Could you try zipping them first?

[ofer]

Good idea. Im used to systems that scan inside zips, so I didn't consider it

face.bgeo.zip