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medzo
02-03-2018, 12:57 PM
Hi

I am having trouble in understanding environment light.

In an architectural interior scene I have set up distant light (sun), environment light (sky with backdrop) and portals.

In Global illumination tab / Brute force I have unchecked Sample backdrop, and in surfaces reflection / refraction options set to Raytrace only.

Here is the problem. Environment light is the biggest contributor to noise. I need to set it up to 128 samples with 16/32 camera samples to get clean result - render times are expensive. If I disable environment light and use only portals I need just 4 samples to get a nice result and render times are ok. But now, everything out side that is seen through glass windows is without specular (cant remember if also without any diffuse...ummm... sorry for my english) since in surfaces everything is set to Raytrace only.

How to set up proper interior lightning with portals and without environment light. Or is this just wrong and we always need to use environment light + portals?
Another question. Does it matter where portals are placed? Inside or outside?

Thank you
Matej

djwaterman
02-03-2018, 04:32 PM
I don't think an environment light makes much sense for an interior.

lardbros
02-04-2018, 02:13 AM
So, you want to light an interior scene AND have the exterior look nice too, through the windows?

Environment light isn't usually a good option for interior lighting, and portal lights only look at what's set in your backdrop options.

What are your GI rays set to?

medzo
02-04-2018, 02:35 AM
Yes, this should be a simple architectural interior.

In backdrop there is HDRI or even dp_sunsky, and as I understand, portals are used for bringing backdrop light (colors) into interior. Lw docs suggest to set all reflection and refraction options to 'RayTrace Only' and sampling BG in BruteForce tab should be unchecked. This means that all surfaces lit by portals will behave correct, but anything you see outside windows (especially when having large panoramic windows) will not receive any specular from Backdrop.

Now, I can put environment light for outside surfaces, but of course environment light will reach also interior causing a lot of noise issues - longer render times. And also why should be there portals, if env light is also illuminating interior? Seems that interior illumination is now doubled.

Second option, I can leave env light alone, just using portals, and turn on BG Sampling in BruteForce tab, this means that now I double specular and diffuse on all interior surfaces (portals + BG).

Third option, leave portals, just use environment light (with a lot of samples) + unchecked BG sampling, in this manner all surfaces will behave correct, but again what is then the point of having portals.

I have been watching some vray tutorials, and there is simple: sun+dome light with HDRI + portals. If this is correct, what is correct in LW 2018?

Thank you
Matej

MarcusM
02-04-2018, 03:27 AM
In this scene I had only area lights and standars materials.
139925

139924

In this also only area lights and standars materials. But in windows, duplicated, one as portal and second standard. One increase general brightnessinside and second light "glow" near window. I was not render longer to totally remove noise. Just tests:
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medzo
02-04-2018, 11:27 AM
Hi Marcus

Well, it is not a problem to make renders.

I would just like to understand how to use Lightwave's new system correct. As you see in my previous post, setting up a interior scene is, at least for me, confusing. I find it hard to believe that putting an area light and portal at the same window opening is correct. Or maybe it is? I would like to get more feedback on this topic :)

Matej

RebelHill
02-04-2018, 12:54 PM
Use an area light in portal mode as windows for interiors, use enviro lights for exteriors. Dont bother with BG GI. Surface reflect/refract as RT only, and lights as visible to camera.

medzo
02-05-2018, 04:20 AM
Thank you RebelHill, I always appreciate your input.

But, as you see in attached renders, something isn't working as it should (at least from my point of view).

Note that on all renders in Render properties / Render - Raytrace refraction is unchecked, diffuse bounce 1, reflection and refraction samples both 3. These settings are basically all the changes made from initial setup.

First render is just Distant Light + HDRI Backdrop + portals visible to camera.
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Black windows are a problem.


So, on second render all is the same except portals are not visible to camera.
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Render is better, black windows are gone, but all exterior surfaces are dull (without any specular).

The third render is lit by Distant Light + HDRI Backdrop + portals + environment light
139941
Now render seems to be correct, interior as exterior surfaces behave ok, but the noise produced by environment light is now much more present.


Please, note how render times have risen, is this normal? Glass material is Dielectric, but also Principal shader produces same render times.


I have to say that new LW engine is amazing in exterior renders (as soon as I finish this project I will upload some renders), but interiors are still a mystery to me :)

Thank you
Matej

RebelHill
02-05-2018, 07:28 AM
Ok, so, portals will "go dark" to camera if there's geo behind them (cos they're acting as a "window" to the BG image).

What you dont want to do is have portal lighting AND enviro lighting (cos then youre double lighting your scene).

Your situation with a mix of interior/exterior just requires the right mix... do this.

Isolate (as objects or layers) the exterior bits of your scene from the interior ones... use enviro to light the exterior, everything else excluded, vis to cam off. Use portals to light your interior parts, excluding exterior stuff, make sure they have normalise off and make them unseen by cam (also place just outside the window, no inside it). Set affect spec OFF for both of these. Then add another enviro light, which excludes nothing, has affect diffuse off (so its lighting nothing) but spec on and vis to cam ON.

Lighting for exterior will come from enviro1, light for interior will come from portal, and traced BG refract/reflect will come from eviro 2.

You'll find all sorts of details of such setups, how to optimise renders for speed, etc in the training here...

http://forums.newtek.com/showthread.php?155497-New-video-training-for-2018

medzo
02-05-2018, 10:28 AM
wow, this just blew my mind...

thank you RebelHill

medzo
03-09-2018, 01:57 PM
Hi

My question is mostly for architectural visualizations.

What are benefits from using environment light? (besides making you want to buy a better computer to get rid of the noise :) )
Seems there is a lot of setting up. Materials need to be in raytrace mode, disabe gi in brute force panel, separate model to interior/exterior, enable this and disable that ...

Is lightning with Environment light more 'realistic', more accurate, ... Why not just use Distant light for Sun and Backdrop lightning with Sample backdrop in Brute force tab enabled? Is it less 'realistic', specularity isn't correct or ...
Of course I have rendered both ways. Renders are a bit different, but not really much. Renders with environment light do seem to get more of the sky color, but is this worth all the noise that comes with? Or is other method just an old legacy method of lightning up our scenes?

Matej

djwaterman
03-09-2018, 05:12 PM
Looking forward to seeing these images when done.

lardbros
03-10-2018, 01:57 AM
The environment light is only beneficial for its multi importance sampling.
It isn't less or more realistic, it's different I guess.
Environment light, without GI, will give you effectively the first bounce of GI light.
Environment light, with GI, and the first bounce is already done with the environment light, subsequent GI bounces are handled by the GI.
GI only is more realistic than just the environment light on its own, but you have to crank your GI samples up high to remove the noise.

The trick with the environment light is to turn off anti aliasing completely, crank up he environment light samples high enough (32? Or maybe more) to remove most of the noise, without anti aliasing, and THEN turn OK adaptive sampling but on 0.25 or something fairly low. You'll get surprisingly fast and noise free renders.

medzo
03-10-2018, 06:43 AM
Here I am attaching two different methods.

Guess which is which :)
140583140584

So to summarize, environment light isn't that necessary, it does seem to give better contact shadows and maybe bump in shadowed areas is more noticeable, but as far as general lightning goes it is not any better than regular GI.
And if I understand this correctly, ISBG samples in Brute force tab is doing exactly what environment light is doing?

Matej

djwaterman
03-10-2018, 07:29 AM
I'm guessing the second render is an environment light, only because the rooms look darker inside where that light can't get to.

medzo
03-10-2018, 07:29 AM
wait a minute....

If I use a quality (Peter Gunthie's) HDRI, I don't even need sun (Distant light)... huh...

@djwaterman: well, you are right :) hardly noticeable...

lardbros
03-10-2018, 11:00 AM
wait a minute....

If I use a quality (Peter Gunthie's) HDRI, I don't even need sun (Distant light)... huh...

@djwaterman: well, you are right :) hardly noticeable...

You don't need a distant light with ISBG and GI... Or when using an environment light with an HDR backdrop.

Depending on the size of the sun's light source in the image though, you need to either increase the ISBG resolution, or the MIS resolution in the environment light.
ISBG only only affects sampling from the backdrop.
MIS affects all sampling, from the backdrop, as well as spec... Which is why it helps to get rid of fireflies.

The benefit of using the environment light is that it multiple importance samples, so it helps with fireflies in the spec.
Using environment light AND GI will give the best of both worlds, and look nice too.
For purely external scenes you probably don't need to use GI really, just an environment light works well with an HDR map