Please explain Visibility Map of light source

[FarbigeWelt]

There are 900 simple cubes in all three scenes. All cubes have the same material. The light comes only from sky.
The render times are different with different positions of the cubes. This puzzles me.
I checked the console log for differences. One big difference is the time Visibility Map of light source takes to be done.
Please have a look at the times a render step is done.

Code: Select all

Cloud	Gauss spread	Gauss tight	tight-spread [s]	tight-cloud [s]		
00 00:00:00.00	00 00:00:00.00	00 00:00:00.00	0.0	0	Engine/Final	Rendering layer "RenderLayer"
00 00:00:01.14	00 00:00:01.12	00 00:00:01.68	0.6	1	LuxCore	Building visibility map of light source: __WORLD_BACKGROUND_LIGHT__
00 00:00:01.71	00 00:00:11.32	00 00:00:34.18	22.9	32	LuxCore	Visibility map done in n secs with 1000000 samples (0.03M samples/sec)
00 00:00:05.54	00 00:00:27.89	00 00:00:40.82	13.0	35	LuxCore	Noise estimation: first pass
00 00:00:31.32	00 00:03:45.98	00 00:03:17.06	-28.8	165	LuxCore	Samples per pixel 100%, rendering done.
00 00:00:34.76	00 00:03:51.46	00 00:03:20.51	-30.9	166	Engine/Final	Finished rendering layer "RenderLayer"

The difference of gauss tight to the other two scenes comes with denser positioning of the cubes.

Cloud, openCL Hybrid

Gauss spread, openCL Hybrid

Gauss tight, openCL Hybrid

Please give me an explanation for the render time difference of more than 3 minutes. Thank you.

[B.Y.O.B.]

In an open scene like this where all the sky is visible the visibilitymap is useless and should be disabled.

[FarbigeWelt]

In an open scene like this where all the sky is visible the visibilitymap is useless and should be disabled.

Okay. Looks like I have over looked this feature. How can I disable the visibility map?

[B.Y.O.B.]

World properties, performance panel.

[lacilaci]

This is why I would hope the new cached one could work in all cases.

Unlike portals which ppl know how to use in general, visibility map is different approach which you guys even dub as "auto-portal".

It gives the impression it works all the time(especially since it is on by default) And after several product renders I accidentaly found out it is pretty damaging to performance in productviz situations.

Unlike portals which need to be put in scene, there is no way a user knows that this visibility map should be turned off in some cases.

So maybe if it couldn't be made so it works all the time giving optimal results, maybe there could be some test which could determine if the map is efficient to use and if not luxcore would auto-disable it in those cases?

EDIT: Or maybe put it in rendersettings somewhere visible?

[FarbigeWelt]

World properties, performance panel.

Thank you for the fast support. Would have never looked for it there. Now, I found it.

[epilectrolytics]

... there is no way a user knows that this visibility map should be turned off in some cases.
EDIT: Or maybe put it in rendersettings somewhere visible?

Same here.

I always forget to check this so it is mostly working no matter if necessary.
In the Blender Development thread I suggested to bundle all cache settings in the render properties.
It was then explained to me how those caches have different functions, light related, render relater or else and are in the right place to be. That's true but it is very much complicating the user experience.

I am used to go through the render settings from top to bottom and what's not listed there I will likely overlook.
Visibility maps/caches are general settings for all (infinite) lights, (individual maps for different background lights make no sense) and would be better represented as render settings (maybe under light strategy where DLSC already resides).

[B.Y.O.B.]

You are making very good points, I'll improve this during the 2.8 port.

[epilectrolytics]

Thanks!

[Sharlybg]

This is why I would hope the new cached one could work in all cases.

Unlike portals which ppl know how to use in general, visibility map is different approach which you guys even dub as "auto-portal".

It gives the impression it works all the time(especially since it is on by default) And after several product renders I accidentaly found out it is pretty damaging to performance in productviz situations.

Unlike portals which need to be put in scene, there is no way a user knows that this visibility map should be turned off in some cases.

So maybe if it couldn't be made so it works all the time giving optimal results, maybe there could be some test which could determine if the map is efficient to use and if not luxcore would auto-disable it in those cases?

EDIT: Or maybe put it in rendersettings somewhere visible?

At some point people need to learn a bit the engine they are working with. Even with a manual portal approach user should understand that space with large openning could give worse performance.
so for such kind of detail i think a simple warming tooltips is enough.