Cutoff vs. Dim Distance

[Deflaminis]

Just sort of curious which sorts of conditions one is preferred over the other. Are they basically the same thing, except that cutoff also affects refraction? If I'm trying to optimize a scene that is being burly, is there ever a case where I might want to adjust both of these at once?

Thanks for any tips!
AJ

[joconnell]

Cutoff is how much of a difference the reflection has to make to the overall material before it's not considered anymore - 0.01 or 1% might start getting shown up as reflections cutting off harshly in gamma 2.2 setups so if anything it might be a bit high, especially in subtle scenes. Dim distance can be quite useful for blurry reflections - if you've got a very soft reflection, only the close things are really that distinct, further away bits turn into ambient mush so you might get some speed or cleanliness benefits from this one.

[Deflaminis]

When you say difference, do you mean sort of a contrast difference? (Like noise cleanup?)

Thanks!
AJ

[^Lele^]

I believe its unit is the standard Float Value for the light (as in rawLighting RE Value) and reflectivity amount for the Shader (or the reflectionFilter RE values).
Same goes for lights, *I Think*, in that when the light intensity on a surface is below the cutoff threshold, that light won't be considered on that surface anymore.
I say *I Think* because that's what can be inferred from the Manual for 3.2 for the Lights: "Cutoff - this parameter specifies a threshold for the light intensity"
It's a bit more murky in its wording for the reflection part in shaders, but i believe the behaviour is exactly the same (well, backwards ^^)

Below an interesting test which demonstrates the cutoff is indeed a float value for the lights:
Fully white plane to shine the light on (so that it looks just like the RawLighting RE), and a light cutoff of 0.5:
The last "fully" shaded pixel (ie. at the net of the AA performed on the light cone edge) has a value of 0.5, then the lighting stops.


For the shader. the cutoff is the REFLECTIVITY AMOUNT (as can be color picked in the reflectionFiler RE) of the shader at the shaded point, as can be seen here (Beauty and RefFilter):
The cutoff was 0.085 in the shader, the last reflective pixel in the ReflectionFilter has that value.

[^Lele^]

Aaaand, to answer your original question, distance is user-specified, while it may vary when cutoffs are used (for lights, at least).
I believe max ref distance still obeys the cutoff value (ie. if the cutoff comes sooner than the distance, it stops tracing anyway).

[Deflaminis]

Thank you very much for taking the time to explain that. This is interesting information. Thank you both!