LuxCoreRender Forums

Dade wrote: ↑Wed Apr 03, 2019 1:54 pm

lacilaci wrote: ↑Wed Apr 03, 2019 1:10 pm Very interesting.. So I've figured there was a shading issue, autosmooth + bevel modifier changed shading and that resulted in the error.
The interesting part is that this type of shading issue doesn't seem to affect cycles at all. This is frustrating

So was it normal interpolation related ?

seems like that. Shading was breaking over beveled edges, this didn't do anything for cycles but made every object weird looking in luxcore. Basicaly it looked like terminator effect but on an edge of a wall.

I can get the behavior much closer now but since much of the scene is directly lit with sky through windows there is a lot of noise in luxcore. I think cycles's portals do much better job than auto visibility solution of luxcore.

luxcore cycles

Ok, so for a loong time now I've struggled with some impossible to resolve noise in luxcore that just takes insane amount of samples to get acceptable.

I've learned that if I have windows and light coming from outside, everything is mostly great with performance... Having "complex windows" that represent multiple openings do have somewhat ugly impact, and here is where cycles's portals do much better work with soft shadowing areas than luxcore.

But it gets worse, if I have also stuff outside windows(translucent leaves and also opaque objects), then complex windows and then interior, luxcore becomes the slowest in rendering direct lighting. Indirect lighting is clean fast(photongi), areas that aren't really touched by overlapping shadows are also clean fast, but some areas are not clean even after thousands of samples. I tried to replicate this on a simple example, but it tends to not be a big issue if I just put some objects outside and some inside, you get to see some struggle with direct lighting maybe but since the scene is simple it still isn't really an issue.

Due to this I've decided to try the tweaked commercial cycles version (e-cycles) which is much slower with GI (no gi caching) but with portals it just destroyed luxcore even with bunch of complex shaders and objects outside windows. I also tried this with new octane render and it is pretty much the same story (but octane is even faster and has very uniformly distributed noise accross the image)

So, can we get portals? And would it solve the problem with heavily obstructed lightsources? Can something else be done about this?

Again, to summarize the problem I'm experiencing over and over again: areas with very soft shadows are incredibly noisy and take forever to clear.

here's direct light only (Diffuse and glossy depth at 1)
this is the type of noise/area that e-cycles and octane clear in an instance (probably thanks to portals)

...continuing.

Something interesting about octane, not even sure if normal behavior...

Octane doesn't even try to sample skylight until you want GI bounce (at leas 1 bounce must be enabled for octane to sample skylight without portals)
So if you enable direct light only, octane won't do anything for interior unless there is a portal, then it works but only for portals, for outside you need at least one bounce.

octane no portals (0 bounces): octane no portals (1 bounce enabled): octane portals with 0 bounces: for comparison, luxcore with direct light only: Note that luxcore is actually tiny bit better when compared with octane-no portals (because luxcore at least has the visibility map) however octane completely destroys luxcore+visibility map when you use portals. And it's a similar story with cycles or corona, portals seem to help a lot more than visibility map when direct light related noise becomes a problem.

Again, there might be more that goes into this problem. I'm not an expert and I would like to be able to get perfect performance without portals, but it seems current solution (visibility map) is very weak when compared against popular "portal" type of solution.

Edit

example Blend file to test ?

This one should work...

But any interior with disabled GI should provide ~same results with poor direct light sampling

No hDRi in the file. so test was done with flat background ?

yes, flat color

the octane result gets near clean in 30 seconds / ~1000 samples no denoising.

luxcore after 5000+ samples / 5+ minutes looks worse than a 10 sec octane rendering. Which pretty much means this noise won't go anywhere and in some more complex situations than this one nothing can help.

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: