Astronomical render times with multiple layered refractions

[SonyBoy]

Is there anything that can be done to speed up render times with refractions? This seems to be something that can be incredibly slow for Vray, especially with multiple refracting objects layered over each other and glossy refractions and reflections. I have a scene with nested glass tubes inside each other and the render times are insane, even with a global ray limit of 10 (roughly the number of bounces I need).

Rendering with a 4K HDRI currently... would reducing the resolution of this help? Never quite clear how much the content/resolution of the HDRI affects render times, but it always seems that Vray hangs forever on a few tiles at the end of renders....

[Morbid Angel]

Its a tricky one, if you think about it you are multiplying the reflection and refraction rays x10 fold for every trace, I don't think any renderer will have luck rendering such scene really fast. Its why other methods exist to simulate glossy/blurry refraction without actually doing true refraction trace like volumescatter or fast sss. Not sure what is the outcome of your look of course, if its just a slightly blurry refraction those won't do the trick.