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Natural lighting in interior environment

A few questions (many, actually) about interior archviz lighting:

a) What is the best way to recreate a natural lighting in an interior environment with relatively small windows?

b) Should I use a skylight for interior environments?

c) My current solution involves a directional light with intensity around 5 and an Indirect Lighting Intensity around 75. The result is kind of acceptable, but I get a lot of artifacts, especially in the corners, plus I had to lower a lot the diffuse boost of some object in order to avoid excessive color bleedings on the environment. Is this setup correct?

d) I've seen that in the realistic render sample some spot lights are used to fill in, would this help in reducing artifacts?

e) How should I size up the lighting importance volume? Why smaller values are causing very dark lightmaps and why larger volumes seem to reduce lightmaps' artifacts?

f) How can I avoid banding on the lightmaps? In some cases I'm already at 512, should I go even higher in resolution?

g) Are there other parameters I can tweak if I want to achieve very high quality and photorealism in a relatively small environment?

PS: The artifacts I'm talking about are not related to UV layout of the single meshes (e.g. appear also on a mesh made with 1 simple plane) and are probably due to some interaction of different objects in the scene. Thank you in advance for any help!!

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asked Jun 25 '14 at 04:05 PM in Rendering

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devel.bmad
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avatar image cadviz Jul 06 '14 at 04:20 AM

I suggest to study this project, I guess it would be very helpful...:) Realistic Rendering Example

avatar image 00shahaf Feb 21 '17 at 04:06 AM

I see plenty of people struggling with these issues exactly, and the information on this thread is pure gold. It should be made into a series of Youtube tutorials.

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I'm not an artist but can answer some of these.

a) What is the best way to recreate a natural lighting in an interior environment with relatively small windows?

Static spot lights oriented into the window can go a long way for getting high quality area lighting, check out how the Realistic Rendering sample is setup.

b) Should I use a skylight for interior environments?

If you have a mix of indoor and outdoor, the skylight will excel. If you have a bright sky and small windows, it will cause artifacts (although you can combat them by jacking up the IndirectLightingQuality).

c) My current solution involves a directional light with intensity around 5 and an Indirect Lighting Intensity around 75. The result is kind of acceptable, but I get a lot of artifacts, especially in the corners, plus I had to lower a lot the diffuse boost of some object in order to avoid excessive color bleedings on the environment. Is this setup correct?

IndirectLightingIntensity of anything over ~5 is going to expose a bunch of GI solver artifacts and I would recommend trying to find another way. Why do you need that much bounce lighting on the sun? If your outdoors is setup properly (sun + sky light sources) then I don't see why you would need so much bounce.

e) How should I size up the lighting importance volume? Why smaller values are causing very dark lightmaps and why larger volumes seem to reduce lightmaps' artifacts?

Just make sure it contains anything you want to have accurate GI on, or where a dynamic object can go. Usually you do not put background / vista geometry in it, to reduce build times.

f) How can I avoid banding on the lightmaps? In some cases I'm already at 512, should I go even higher in resolution?

Need screenshot to know what artifact it is, there are several: insufficient resolution, lightmap compression, seams.

g) Are there other parameters I can tweak if I want to achieve very high quality and photorealism in a relatively small environment?

For GI, setting IndirectLIghtingQuality to ~6 and IndirectLightingSmoothness to ~.6 will give the best results, with a very long build time. This only affects solver quality, not lightmap resolution or compression artifacts.

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answered Jun 26 '14 at 07:21 PM

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DanielW STAFF
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avatar image devel.bmad Jun 26 '14 at 10:45 PM

Thank you for your answer, it is very helpful and I'm trying to rework my scene accordingly. Unfortunately, with the sun (=directional static light) at 10 and indirect lighting at 1 plus 1 skylight I get the following result: alt text

The scene is based on a real attic, and the size/positioning of the windows are correct, but I get a much darker result. The walls are completely white, the floor textured with a wood material. The areas closer to the window get lit a bit better (but the whole scene is too dark). I haven't used spotlights in the window at the moment, but I was wondering if I could achieve a better starting point before adding additional lights. Should I jack up the exposure of the scene with post process? In this case, how do I handle the blown up part in of the floor which are lit directly?

Adding the skylight has now introduced all these strange artifacts in the corners (not visible boosting indirect lighting). All the UV are correctly pixel aligned, lightmap density is 256, are those the kind of artifacts you were talking about? Setting IndirectLighQuality in this case improved the artifacts, but the one closer to the floor didn't disappear

alt text

avatar image DanielW STAFF Jul 01 '14 at 07:30 PM

In the top screenshot, the blocky direct lighting makes me think you are using a Static directional light. I would go with Stationary, it will have higher quality direct shadowing (among other things).

The leaking around the corners could be one of two things. Either there's not enough space between charts in your lightmap UVs, or your walls are not thick enough. All of Lightmass computations need some thickness on walls, usually 1 foot. Higher lightmap resolutions can help with this to some degree.

On the darkness of the attic bounce lighting compared to what you expect - it could be either a bug in the lighting solver that it is not bouncing enough lighting, or maybe our post process (bloom, tonemapping) doesn't respond accurately enough to bright areas to make it look right when the sun lighting is physically accurate in brightness. It's hard to say. It could also be a lack of local tonemapping.

The new artifact when adding the skylight makes me think the artifacts in your corners are leaking coming from too-thin walls. If you don't ever see outside, you can add a 'hull' around to prevent leaking. You will see something similar in the realistic rendering map. It's hacky, but necessary in some cases where there isn't sufficient blocking geometry to prevent leaking.

avatar image devel.bmad Jul 05 '14 at 12:57 AM

You are right, walls are just planes with no thickness (I'm using something like an external hull, but it's not a completely closed surface and definitely in the second shot there was a bright area behind the wall. I will try adding some thickness or working better on the hull. Would a stationary light impact performances compared to a static one if I don't have dynamic objects?

avatar image devel.bmad Jul 01 '14 at 10:01 AM

Concerning e), I still don't understand why changing the volume size changes the overall scene exposure. Shouldn't it affect just building times and quality?

Why smaller values are causing very dark lightmaps and why larger volumes seem to reduce lightmaps' artifacts?

Concerning f), here is a screenshot of the banding issues I was talking about. Please note that in the screenshot I've further enhanced the artifacts in photoshop, in order to clearly understand the kind of problem I'm talking about. These kind of artifacts seem related to the lighmaps density, and are still visible on flat surfaces in normal conditions. Any suggestion how to avoid them?

Concerning exposure: what is the best way to increase it? On mac, I've added a postprocessvolume with Min Brighthness = 1, Max Brighthness = 1, Auto Exposure Bias = 1, but still the scene exposure changes moving inside the environment (strangely, looking toward a light source brightens the surrounding walls, and looking toward a corner with no light sources darkens them. Shouldn't auto exposure do the opposite if in auto mode? and with my settings shouldn't it be at fixed exposure?)

alt text

f) How can I avoid banding on the lightmaps? In some cases I'm already at 512, should I go even higher in resolution?
Need screenshot to know what artifact it is, there are several: insufficient resolution, lightmap compression, seams.

banding.jpg (8.4 kB)
avatar image DanielW STAFF Jul 01 '14 at 08:22 PM

I still don't understand why changing the volume size changes the overall scene exposure. Shouldn't it affect just building times and quality?

That's definitely a bug, I don't know what is causing it. A pretty scary bug too.

here is a screenshot of the banding issues I was talking about.

Those are artifacts from the lightmap encoding we are using + DXT compression. There are a not a lot of ways to work around it right now. Lightmap resolution only makes the pattern smaller. We could expose uncompressed lightmaps but then your memory usage would go up by 6x.

Concerning exposure: what is the best way to increase it? On mac, I've added a postprocessvolume with Min Brighthness = 1, Max Brighthness = 1, Auto Exposure Bias = 1,

Auto exposure only works with DX11 atm, Mac drivers only support DX10 level features. But yes, your settings of making the min and the max the same value will hardcode the exposure and that's the expected way to set a fixed exposure. It might be that with the DX10 path (Mac), those settings don't work. I'll have to ask around here. Otherwise, make sure your PP volume has 'unbound' checked so it applies everywhere.

avatar image devel.bmad Jul 01 '14 at 10:17 PM

You were pretty right! Fixed exposure is working correctly, I was just exiting the bound of the PP volume, checking "unbound" did the trick.

So, following your advices I more or less managed to set up my scene. Indeed, the artifacts I'm experiencing do not seem to be bound to very high indirect lighting (they are more or less the same at 75 as at 6), but seem to be more then else the compression artifacts you were talking about and other linked to areas lighted only indirectly and in dark corners: alt text

Are there other way to improve these artifacts? (e.g. without adding artificial lights, that indeed seem to help?) What is the cause of these artifacts?

What kind of artifacts should I expect from very high indirect lighting?

avatar image DanielW STAFF Jul 02 '14 at 12:25 AM

Do those artifacts persist with higher resolution lightmaps? That's a fairly low resolution you are using.

What kind of artifacts should I expect from very high indirect lighting?

Splotchiness and noise, some leaking. However jacking up the IndirectLightingQuality like you did should cancel that pretty effectively.

avatar image devel.bmad Jul 02 '14 at 01:55 PM

Do those artifacts persist with higher resolution lightmaps? That's a fairly low resolution you are using.

Actually it is already at 512, I don't think this kind of problem depends neither from density nor from the UV layout (eg in some cases I used a mesh with a single rectangular plane to check this and found the same kind of artifacts) As I said, I can pretty solve this problem with additional spotlights, but I would be interested to better understand the cause of this problem. alt text

avatar image cadviz Jul 06 '14 at 04:24 AM

I suggest to study this project...Realistic Rendering Example... I guess it would be very helpful...:)

avatar image devel.bmad Jul 07 '14 at 08:56 AM

Yes, I keep on studying it ;-) very useful indeed, though the lighting of the scene is much simpler than mine, due to the fact that in this project there is just a single mostly rectangular room. Anyway, understanding were artifacts come from is always useful to improve the general quality of my work :-)

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