LuxCoreRender Forums

First of all something about all the direct light tests I have seen recently and I'm sure you are not aware: when you set max. path depth to 1, BlendLuxCore exports a value of 2 (I think it always exports "n + 1").

Why ? Because so you can have MIS and MIS is pretty mandatory to render glossy surfaces. So it is a wise behavior and BlendLuxCore tries to not let you shoot in your foot.

However, this has clearly a huge impact on the direct-light-only benchmarks you are trying to do lately. LuxCore traces 2 times the rays Cycles does. Indeed, I do my tests outside Blender, setting correctly the max. depth values.

Now this is a 128 samples/pixel done with Cycles:


and this a 128 samples/pixel done with LuxCore (with a max. path depth of 2, like exported by BlendLuxCore):


I would say that the amount of noise is exactly the same (very low).

Now, let's repeat the same test with LuxCore and really use a a max. path depth of 1:


Same result tracing less rays but it is not a surprise, there are no glossy surfaces at all.

If you are bench marking noise, use the same samples/pixel. If you are bench marking performance use wall clock. Don't mix stuff (noise and time).

thank you for clarification.
So when i use max path 1 in luxcore what i should do in cycles to match lux behaviour ? for this test cycles was set to max bounce 0.

But i don't think it is like you say. just test it and Cycles 0 bounce match luxcore 1 bounce visually. And as soon as you set cycles to Max 1 and Diffuse 1 you start to have indirect bounce and luxcore have to be set to Max = 2 to match Cycles Max and Diff = 1

And when Cycles is set to Max 2 diffuse 2 we can see a clear distinction between the white surface and the bottom dark line caused by the cliping camera distance cutting geometry.

This dark line can only be see in Luxcore at Max = 3

Sharlybg wrote: Fri Aug 09, 2019 10:33 am But i don't think it is like you say. just test it and Cycles 0 bounce match luxcore 1 bounce visually.

You can not do LuxCore 1 bounce if you are using Blender as I have explain. Just export the scene in text format, open the .cfg and check the value of "path.pathdepth.total". It is 2 even if you set 1.

Having a value of 2 doesn't mean you will have indirect light, the extra bounce is used only for MIS (not for indirect lighting).

Make the floor glossy with a very little roughness and Cycles is doomed without tracing additional rays.