Guys I have problems with figuring out how to control refraction when using interpolation with universal method (BF + LC). When I’m setting refraction glossiness to let’s say 0.7 and set default interpolation I’m getting like sand glass effect. But let’s say I want less blurry glossiness so I’m setting glossiness to 0.9 (keep interpolation settings the same) hit render but it looks exactly the same as with glossiness 0.7 ! I tried laying with interpolation settings but I totally don’t get it. Any tips?
id think if you are using the “universal settings” with a decent low noise threshold, you shouldnt need interpolation? normally the refs are super-oversampled anyway in this setup. since the interpolation always blurs the hell out of the refs, im not surprised your getting a similar result at 0.9.. try dropping the pass rate to 0.. but then it kinda defeats the main purpose of interpolation.
I never had much luck with interpolation in such cases. I find it is mostly useful where you need very glossy refractions and the blurriness works for you. In less blurry cases i just dont use it.
I tried to use interpolation because with universal it rendered much much faster…
good point 
id forgotten about the speed advantage.
the interpolation settings might have their usefulness improved if you could do finer increments on the prepass rate. probably introduce all sorts of rendering errors, but if you could set the prepass rate to say.. -.3 youd get a speed advantage and some blurring, but it would be more controllable.. at the moment -1 is very blurred, and 0 offers no speed boost. ive had no luck with different settings in the min and max rate.