### Weighted delta tracking question

Posted:

**Sat Nov 11, 2017 3:57 pm**Hello,

I read the recent paper on Spectral and Decomposition Tracking by Kutz et al.

http://drz.disneyresearch.com/~jnovak/p ... index.html

I want to use weighted tracking methods in my own toy path tracer.

Following the PBRT book pg 889, the incident radiance is composed of two terms: the radiance arriving from the distant hit point Tr*Lo and the inscattered radiance integrated along the viewing ray.

I evaluate only one of these terms probabilistically. The first, term if no collision was generated, otherwise there is a scattering or absorption even.

As per PBRT I need to weight Tr*Lo with the probability that no interaction takes place, i.e. the probability to hit the surface p_surf. Thus the estimator is Tr*Lo/p_surf.

However, I cannot figure out how to determine the weight Tr/p_surf.

So how is the inscattered radiance combined with the background?

I also took a brief look at Novak's Ratio Tracking paper but there I also failed to find an answer.

Cheers,

I read the recent paper on Spectral and Decomposition Tracking by Kutz et al.

http://drz.disneyresearch.com/~jnovak/p ... index.html

I want to use weighted tracking methods in my own toy path tracer.

Following the PBRT book pg 889, the incident radiance is composed of two terms: the radiance arriving from the distant hit point Tr*Lo and the inscattered radiance integrated along the viewing ray.

I evaluate only one of these terms probabilistically. The first, term if no collision was generated, otherwise there is a scattering or absorption even.

As per PBRT I need to weight Tr*Lo with the probability that no interaction takes place, i.e. the probability to hit the surface p_surf. Thus the estimator is Tr*Lo/p_surf.

However, I cannot figure out how to determine the weight Tr/p_surf.

So how is the inscattered radiance combined with the background?

I also took a brief look at Novak's Ratio Tracking paper but there I also failed to find an answer.

Cheers,