Hello, This is my last attempt to make interior scene with LuxRender. I tried different settings to render it and finally used those below. Now I doubt if it is possible to get noise free render in LuxRender at all. This scene was rendering for ~30 hours and it is still not clear. I would be very gratefull if anyone have an idea why? And what is wrong with this render settings. I have used one light source only. Envoirment map as light source and portal in the window. Scale is correct.
It’sad to say but Lux Render it’s an excellent Engine ,but we should have the computing power of the CERN,for have decent render in reasonable time…
Maybe it would be better for everyone if CERN was render farm not black holes generator 
But I belive it wouldn’t make render noise free too. If every pixel is calculated as average from many rays why is so much difference between two neighbouring pixels?
First, I think you should use a bidirectional integrator in a internal rendering such as this. It’s hard for a path tracer to find the light sources in this scene.
Other than that, you’re using the hybrid integrator, which hasn’t seen much development in some years. Unless you need some specific feature only present in Classic Luxrender, you should also use one of the LuxCore integrators that are faster and are being actively developed. Give LuxCore Bidir a shot. If you have a recent and fast GPU you could also try an OpenCL mode, which can do this kind of scene by brute-force
Don’t use Hybrid Path, it’s an old engine that never worked that well. Also, the low discrepancy sampler is a “dumb” sampler that will not detect which parts of the image need more samples.
In interior renders like this you don’t want a simple pathtracer but a bidirectional pathtracer instead, so use that in combination with Metropolis sampler (a “smart” sampler).
The portal mesh should have as few faces as possible, best is something like a plane a bit bigger than the window.
Last but not least you can also get the latest 1.5dev build and render with LuxCore, this alone will speed up the render speed about 600%, at the cost of losing a few features that are not yet implemented in LuxCore (like portals).
Take a look here: http://www.luxrender.net/wiki/LuxBlend25_LuxCore
edit: and of course you can use a true GPU engine like Path OpenCL in LuxCore - you will lose the perks of the bidirectional engine, but if your GPU is much faster than your CPU, it will probably be faster because of sheer brute force.
Hello, Yes I know all those basics. Portal is a single plane. I tried metropolis before. It was stucking with some areas and not rendering others this is why I am using slower but better sampler. I am using 1.4 with LuxCore but didn’t noticed any speed up after switch. So maybe I will try to render it with Cycles. Sorry for my English which is as bad as my render
Here is the cycles version. 20 hours and it has the same noise level. So cycles seem to be faster than Lux. 4-8 light bounces.
And B.Y.O.B. Lux 2.5 is exporting mesh geometry 6 times faster. But not rendering 6 times faster. Anyway Lux has huge advantage over cycles - You can change lightning after rendering and You can pause/resume rendering. Thats why I like to use it.