Env. Light Visibility Cache

[kintuX]

IMHO...
Simply put, GI & Environment Caches are not intended nor designed for direct lit aka "open" or "outdoor" scenes.
Performance hit can also be experienced in Corona & VRay.
'Just, don't use sports car to plow the fields.'

[lacilaci]

IMHO...
Simply put, GI & Environment Caches are not intended nor designed for direct lit aka "open" or "outdoor" scenes.
Performance hit can also be experienced in Corona & VRay.
'Just, don't use sports car to plow the fields.'

Well, my assumption is that the cache/vis.map exists in stead of portals as a better "automatic" solution.
But in reality it doesn't work that way.
You cannot simply leave it on and expect it to work. I already shown 2 very different examples where it doesn't work and between those is a big area of cases where it requires user to do some per case testing to find out if and how well it works. In comparison to portals which are always working as expected and user either needs them or not and also know where to place them.

Corona and Vray both use portals not a visibiity map so there is no performance hit cause a user simply knows to not put a portal in a fully open scene, something visibility map doesn't know and damages performance by default!

I know corona devs plan to make something like auto portal but I would assume they again gonna go for something rather complex maybe built around pathguiding and who knows what, that cannot be used by gpu rendering.

But let me state again, I like the idea, but it's impractical and sometimes plainly not working(as of now). Compared to portals, which clearly work and it is a concept everyone is familiar with. I'm just a bit afraid that they won't work with bidir and that's why Dade avoids them, hopefully that's not the case

[B.Y.O.B.]

Thanks for your feedback lacilaci.
I agree with you, while testing the vismap cache, after a while I wished we had portals. Besides the arguments you made, with portals you also don't have to worry about persistent caching in animations (which only works if nothing moves).

Maybe a case can be made that with portals, you pay a constant cost during the whole rendertime (by having slightly lower samples/sec performance) while with the cache, you only pay once upfront and then have better samples/sec during the render, but you only get a benefit from this in longer-running renders (and a tremendous penalty in animated scenes where geometry moves, because you have to recalculate the cache every frame).

I have set the default vismap to "none" now.

I'm just a bit afraid that they won't work with bidir and that's why Dade avoids them, hopefully that's not the case

I don't think so, we had portals in old LuxRender and AFAIK they worked with Bidir.

[Dade]

I tried my old scenes, the problem always appears when there is material with a normal map in the scene.

It was this (viewtopic.php?f=4&t=1229#p14746) and it should be now fixed.

[Sharlybg]

I understand the point of moving the default setting to none by default. It is the way to go as Luxcore community will mostly be composed of new Users.

But the new cache work very well in case it was designed for ( Interior scene lit by small to average opening). Also the 1min or less building time isn't that bad if you compare to the time gained while render at the speed it provide.

Maybe manual portal can be add for those situation uncovered by the current cache but not removed.
About manual portal i remenber it wasn't a 100% working solution and can also lead to worse performance in some case.

[lacilaci]

I understand the point of moving the default setting to none by default. It is the way to go as Luxcore community will mostly be composed of new Users.

But the new cache work very well in case it was designed for ( Interior scene lit by small to average opening). Also the 1min or less building time isn't that bad if you compare to the time gained while render at the speed it provide.

Maybe manual portal can be add for those situation uncovered by the current cache but not removed.
About manual portal i remenber it wasn't a 100% working solution and can also lead to worse performance in some case.

I'm actually not sure if none by default is best.
One thing I'm sure about is that the setting should be somewhere in performance category of render settings (even on by default could work as long as we don't have portals) but tooltip should inform about possible shortcommings. Everybody runs through render settings, but you don't expect some important performance setting in world light setting.. I think.

Overall, my main point here isn't "give me portals!" But that if we can't have a fully automatic solution that users don't have to care about, we might actually be better off with portals.

Also, no portals cycles and none vismap setting in luxcore tells me that luxcore's direct light performance is really bad overall. So maybe another way of looking at the situation could be: leave single map as is, but rather improve overall performance of direct illumination? I just think, portals are quickfix for the situation as it is now, but there might be a room for improvement elsewhere.

I understand this is basically on Dade's shoulders and there's only so much time a person has to explore endless possibilities, but I also think we shouldn't just shrug our shoulders and be like: it is what it is, let's just be happy.

[B.Y.O.B.]

Maybe we can devise an algorithm that detects which kind of env. light accelerator (none, single map, cache) would be best for the scene?
Shoot 1000 rays in all directions from the camera and check how many hit the infinite light?

[lacilaci]

Maybe we can devise an algorithm that detects which kind of env. light accelerator (none, single map, cache) would be best for the scene?
Shoot 1000 rays in all directions from the camera and check how many hit the infinite light?

I can see something like that for none VS single map cases. So that open space will not have issues and at that point default single map ON setting is best.

However I'm not sure about cache, if those patches can't be fixed it's unreliable and I would not risk using it at all.

Maybe a compromise solution could be a mix of things.

1.autodetect if none or single visibiity map is best and have luxcore turn it on/off
2.add portals so that complex scenes have a solution (if those artifact patches can't be solved)

As a result, users don't have to worry about open scenes vs basic interiors, but there would be still a way to boost complex interior spaces. Right now biggest source for some interiors is not GI but actually direct light/shadows noise.

[Sharlybg]

However I'm not sure about cache, if those patches can't be fixed it's unreliable and I would not risk using it at all

Can you provide a small scene that show the issue ?

[lacilaci]

However I'm not sure about cache, if those patches can't be fixed it's unreliable and I would not risk using it at all

Can you provide a small scene that show the issue ?

What do you mean? The scene is in the attachment where I posted some results.