Indigo Renderer Forum

What is back scattering? How does it affect the material?

the roughness of the surface, basically more backscattering == flatter looking.

for more information and examples, google "oren nayar" and check the first hit.

I found this in the Technical manual the other day:

Nice, but the images are a bit small for their complexity..

Wikipedia ftw

The above pictures make no sense to me. Sigma = 0 in the wikipedia article looks like Sigma = 1 in the technical manual. According to wikipedia, a higher value for sigma makes the model look more flat, but with indigo it looks flattest with the lowest sigma setting.
Is it just me? Or did something get mixed up?

Polinalkrimizei wrote:The above pictures make no sense to me. Sigma = 0 in the wikipedia article looks like Sigma = 1 in the technical manual. According to wikipedia, a higher value for sigma makes the model look more flat, but with indigo it looks flattest with the lowest sigma setting.
Is it just me? Or did something get mixed up?

Is it possible ono somehow implemented the function...backwards?

Polinalkrimizei wrote:The above pictures make no sense to me. Sigma = 0 in the wikipedia article looks like Sigma = 1 in the technical manual. According to wikipedia, a higher value for sigma makes the model look more flat, but with indigo it looks flattest with the lowest sigma setting.
Is it just me? Or did something get mixed up?

It just depends where the light comes from - sigma increases backscattering.

Could someone please describe back scattering for the well... unitiated?

Polinalkrimizei wrote:The above pictures make no sense to me. Sigma = 0 in the wikipedia article looks like Sigma = 1 in the technical manual. According to wikipedia, a higher value for sigma makes the model look more flat, but with indigo it looks flattest with the lowest sigma setting.
Is it just me? Or did something get mixed up?

i got the same impression; the wiki images are in line with my expectations.

anyone wanna render some spheres?

like the wikipedia image. 0, 0.1, 0.3

I wasn't either under the same impression than you, polin and lyc. Higher sigma seems to darken the surface, however if you observe closer you can see that the dark rim edges are also fading away, see below.

I'm fine with the actual implementation

While on the "topic"...
Can the Torrance-Sparrow model for Phong be implemented, Ono?
Or is it too much of a hassle?

Thanks for the clarification guys.
CTZn, your image made it pretty clear and now I think I got it!

clearly visible the higher the sigma the darker the material gets!

This is something I never understood...



(About my old Statue render on the top... simply drag & Drop the image into a new Firefox Tab to see it in Full size Neo, the forum scales images down!)