Question about HomogeneousMedium::Sample implementation

[Immocat]

I'm a little bit confused by the implementation of HomogeneousMedium::Sample.

Around line 57, homogeneous.cpp(Also at Page 894 in pbrt3 book)

Float dist = -std::log(1 - sampler.Get1D()) / sigma_t[channel];
Float t = std::min(dist * ray.d.Length(), ray.tMax);

As far as I know, the dist is the sampled distance over [0,+inf). For rays ( o + d t ), `dist == t ray.d.Length(), andt = dist / ray.d.Length()`.

Why the code is dist * ray.d.Length()? Maybe I misunderstand something, or it is a bug here.

[mmp]

Thanks!