[fixed bug] max_extinction_coeff explained

[CTZn]

I'm pretty sure this bug was squashed already, unless if it is depending on some local circumstances (not a systematical bug) because my clouds scenes are rendering alright iirc.

So here is a mesh with a scattering shader output aiming at 2,500.0; it renders clear, while setting scattering to a uniform spectrum of 2500.0 will give the expected result.

I also tried crazy high absorbtion with uniform values and the results were not convincing on this human head sized object... until I deactivated scattering; wether shader or not it is bugging absorbtion.

I'm not sure what this is about. Someone else noticed ?

Spotted with Indigo 3.8.16, present in 3.8.26.

[OnoSendai]

I think you need to set max extinction coeff properly.
It should be set, in this case, to 2500.

[FakeShamus]

can this be explained a bit more? I never know what to set the max extinction coeff so it's always left default, but how exactly is it used? are there other situations where it should be set differently?

[OnoSendai]

max_extinction_coeff should be set to the maximum extinction coefficient that the medium will take at any point.
The extinction coefficient is the sum of the absorption and scattering coefficients.

max_extinction_coeff determines how large a step along the ray Indigo can take when it is calculating participating media. The larger max_extinction_coeff, the smaller the steps need to be.

max_extinction_coeff is only used when the medium is heterogeneous - that is when then the scattering or absorption coefficient varies with position. This will be the case when a shader is used for the absorption or scattering coefficients.

[CTZn]

Ah well we have learned something new today, plus it's not a bug, great !
We can take, and actually need to know such tech details.

Thanks !