LuxCoreRender Forums

B.Y.O.B. wrote: Mon May 06, 2019 12:38 pm I also find that soft shadows take forever to clear up in LuxCore in this scene, for example the area on the right.

I have tried to make the LuxCore and Cycles setups match more:
- removed the sun (hard to get same brightness)
- disabled clamping
- set Cycles to direct light only
- set Cycles background to same settings as LuxCore (white color, gain 150)
- created portal for Cycles (on layer Alt+1)
- set both to 100 samples (not comparable, but at least in same ballpark)
- disabled denoising

Here is a comparison between Cycles and LuxCore after these changes:

And you used normal cycles,

e-cycles is over 50% faster and much cleaner with lower sample count and you can even use dithered sobol + ray scrambling to further increase performance and noise uniformity... And new cycles adaptivity will make things even faster yet...

And keep in mind this is still a very simple scene, where direct light shadows can be easily hidden with GI caching. But a relatively dark interior with complex reflective surfaces can make Direct light shadows very prominent and visible and luxcore might not be even able to get acceptable noise levels.

This means you will get sometimes bigger and sometimes smaller areas with a heavy noise that will look terribly even after denoising. I've seen this in some testscenes, in my office project, in my latest project where due to this issue I went for e-cycles instead...

I think it is just visibility map being an inferior solution for certain cases against portals. But it might be a bug or something idk...

I think this performance translates also to gi (no PGI) where shadows are way too dark and poorly sampled and the whole gi starts looking weak/dark and also tends to slow down progressively where even high sample counts don't do much.

If I compare this head to head with e-cycles I get this in a minute in luxcore (no pgi, 8 path depth for gi): and this in the same time with e-cycles (no ao, no scrambling and no dithered sobol, 8 path depth for gi): notice that e-cycles also gets much better and natural looking light distribution.

I sometimes wonder if this isn't due to older shader model. Don't know where i read it but newer shader model are faster to sample.

Sharlybg wrote: Thu May 09, 2019 1:55 pm I sometimes wonder if this isn't due to older shader model. Don't know where i read it but newer shader model are faster to sample.

I don't know, maybe... But it's super annoying cause I have product viz scenes where luxcore is faster and then others where cycles is faster, and same with interiors...

No portal in the E-Cycles version ?
Is it the same with HDRi instead of flat background ?

Sharlybg wrote: Thu May 09, 2019 2:06 pm No portal in the E-Cycles version ?
Is it the same with HDRi instead of flat background ?

e-cycles does use portal and luxcore visibility map. Hdri or not, situation is always the same.

e-cycles does use portal and luxcore visibility map. Hdri or not, situation is always the same.

So now just wonder how e-cycles look without portal. maybe our visibility map is less efficient.

Sharlybg wrote: Thu May 09, 2019 3:43 pm

e-cycles does use portal and luxcore visibility map. Hdri or not, situation is always the same.

So now just wonder how e-cycles look without portal. maybe our visibility map is less efficient.

Yeah, ecycles without portal is close to luxcore. But I don't know if it's inefficiency od visibility map or something wrong with direct light sampling in luxcore to be honest.

I like the idea of visibility map but it might not be enough when exterior is obstructing light too much, here portals seem to help much better.

but it might not be enough when exterior is obstructing light too much, here portals seem to help much better.

So do you mean performance is almost the same or better without obstruction ?

Sharlybg wrote: Thu May 09, 2019 4:54 pm

but it might not be enough when exterior is obstructing light too much, here portals seem to help much better.

So do you mean performance is almost the same or better without obstruction ?

Actually a good question. In this monkey testscene I didn't compare, but in other interior scenes luxcore perf. is fantastic unless there are obstructions outside windows....

Or heavy soft shadows...

Or scene like from my office project where a lot of windows are letting light from different directions also seem to give problems.

I don't know really what's up with that, unpredictably luxcore sometimes throws a ton of noise where it seems it shouldn't be a problem. Ecycles is much more predictable in that area and there is something you can do about that noise.

So atm I always test in first stages of a project if luxcore runs smoothly or has problems and then go for ecycles or octane depending on the situations.

Octane for productviz, ecycles for more complex stuff and luxcore whenever it works.