Iray and the Single Light Source
I'm trying to create a scene within a closed room that has no windows and only a single light source coming from the ceiling light. I thought that with Iray's physics based lighting this would work well, but as soon as I add a character the side of them that isn't facing the light is plunged into almost total darkness, no matter how bright I make the light source. Their shadowed side is just far too dark for the amount of light thats in the room.
So my question is - Is it possible to light a room well with just one light source in Iray (like you can in real life), or do we still have to use multiple sources like we did with 3Delight?
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I'm doing something very similar right now. I think it is possible. First what emission settings are you using?
Since light itself travels in a straight line until it hit something and bounces, it really doesn't go around corners. You see the cheat all the time in the movies when they have the light from no where lighting the actors eyes/face.
What I've been doing is working with primitives and making them emissives and tweaking various settings, including scale, using nulls and having the primitive pointing at the subject while still maintaining an ambient light. Lot's of tweaks and spot renders, but I'm definitely seeing progress.
This is my first render with a single light source with iray - I'm working on a different one right now. ;)
Getting it to work depends on a couple of things. Some are scene elements like wall colors. Lighter colors will reflect more light and so forth. You also should have the enviroment set to scene only if I recall correctly. And lastly you will more than likely need to make adjustments to the tone mapping.
If you took a photograph of a person in a room with no windows and only a ceiling light you would need to change to a faster film (200 or above film ISO) and likely adjust the fstop as well. The same is true in Iray.
And this is the render I just made. It's only a partial because it was taking to long for me, but as you can see the single light source is lighting the scene quite well. Now I understand that this is a campfire, not a lighted room.
While you might want a single source confined by a lamp, depending on the size of the room, reflectivity and everything else Khory posted, it will be far easier to mimic the light you're going after. There's a certain point where the adjust - spot render, adjust - spot render, adjust - spot render syndrome gets really old, really fast.
Iray renders faster the more light there is in the scene so a single source image will take longer than a 2 light render and so on.
tl155180 said:
So my question is - Is it possible to light a room well with just one light source in Iray (like you can in real life), or do we still have to use multiple sources like we did with 3Delight?
It's possible, but the result will be very harsh and unflattering, although it will be realistic. Portrait lighting to make people look good involves a key light, back light and rim light. One bulb in a ceiling light will look like a Nazi SS interrogation!
But, if that's the look you're going for, it should be doable.. The side of your model opposite the light will be very dark. If you change tone mapping settings to get that part of the scene brightened up, the rest of the room will look blown out with light, and very unnatural.
Here's a quick test render I did with conditions similar to what you mentioned.
Scene only
Tone mapping settings:
ISO: 400
Shutter speed: 1/60
Aperture: 2.0
Emission settings: 200 W (Watts)
Temperature: 2900
The room was probably a poor choice...too dark. I put Iray base on just about everything in the scene. Including the skin. *gag* Skin looks terrible...needs a lot of work...
Ah - I see thank you very much, Khory! I'll keep an eye on that along with digging for non-iray shaders. Those slow me down terribly as well. As long as I hit everything at least with the iray base, it's usually pretty good. But let me get some buried detail non-iray stuff in there and whoa Nelly - the old gray mare ain't going anywhere. ;)
dhmohr, I agree that red walls are not going to give you back much light. And I suspect that the warm light and red walls didn't help her skin much either unless it has blue/blue green undertones. It is a good example of a room lit with a single light and the sort of settings you need to do that.
The other thing to be aware of isn't so much to do with light, but with the room itself. A completely enclosed space takes much much much much much much longer to render in unbiased renderers. No idea why; it just does. I had one scene with a character unenclosed that took 10 minutes in Iray (CPU only) and when I put them into a fully enclosed room with exactly the same lighting, it took about 90 minutes.
As far as the light itself goes, is it at all possible for you to put a mirror into the room either to the side or behind your character? That would increase the light effect without adding more lights into the room, in an entirely realistic way.
I just woke up (its morning for me now) - thanks to everyone for your helpful comments overnight.
It seems to me that although Iray is physics based and a big improvement in terms of lighting (for me) it still seems to rely quite heavily on direct light, with areas lit by indirect light being too dark by comparison to reality. So I keep feeling like I need additional lights in every indoor scene just to cheat and even up the direct vs indirect lit areas. I had hoped that we'd left that aspect behind when we moved from 3Delight to Iray and it seems that Iray has improved it somewhat, but I think its still a long way from realistic.
For instance, I was lying awake in my room last night, pitch black except for the light from my bedside lamp, and holding up my arm to the light. Obviously the side that faced the light was well lit, but the side that didn't face it was also reasonably well lit so that I could still see all the details on my skin etc. It seems that Iray, or maybe PBR in general(?), still cannot achieve this without cheating.
Below is an example image to illustrate. The light in the middle of the room is quite bright and the walls are all light and smooth, but the indirect lighting on her back is far too dark, in my opinion, in relation to the amount of light in the room. I was wondering if theres any way to increase the light on her back without actually adding another light to the scene or making the center light blinding?
Thats just a basic lamp with Iray emissive shader applied to the glass surface.
Tone mapping:
EV: 12
SS: 16
F/stop: 8
ISO: 400
Attached pic is a quick render, one point light set about 1 meter in front and above her, she is about 2 meters from the side of a ten meter cube, Iray default settings and set to scene only, the point light is set to 25K Lumen and 100K temp.
Her shadow on the cube is quite light in color, and the parts of her in shadow are not jet black, this is due to light bounce, the light is strong enough to have reached other sides of the cube and is now being reflected back as "fill" lighting.
Point lights normally work best for this as they cast light in virtually every direction, only draw back is all of that light bouncing around needs to be calculated by the engine, which cranks up the render time.
Yep - this is exactly the problem I'm running into. :) The thing is that its not realistic. Try standing in a room at night and switching on just one bright light, then turn away from the light and look down at yourself. You can still see yourself, right?
As far as the light itself goes, is it at all possible for you to put a mirror into the room either to the side or behind your character? That would increase the light effect without adding more lights into the room, in an entirely realistic way.
I think enclosed rooms take longer to render because the light has so many surfaces to bounce off, which means a lot of calculations. Outdoors the light can just go on to infinity, so less of it is reflected back.
Mirrors would look a bit out of place unfortunately, but I'm beginning to think that I'll have to resort to something similar... like maybe making the walls more reflective.
You could do what a photographer would do, have an assistant stand behind her with a gold reflector! :-)
http://www.overgaard.dk/quality-of-light-page4.html
You could do what a photographer would do, have an assistant stand behind her with a gold reflector! :-)
http://www.overgaard.dk/quality-of-light-page4.html
It might come to that! :)
I think you've misinterpreted that picture - the other woman is just a voyeur who was playing over-large frisbee in the park that day.
What would be really useful is if the "Environment Intensity" slider under Scene Only environment settings actually did something indoors. I'm wondering why thats there at all for scene only? Has anyone been able to get it to do anything?
Edit: This is closer to what I'd expect the light in that room to look like, but to achieve this I had to add a softbox behind the figure using a spotlight. Thats all well and good but it adds incorrect shadows and reflects very obvious light onto areas like the lamp stand.
This is a case where upping the environment intensity would be a simple and easy fix. Its a shame it doesn't work.
I don't know....I actually like the first image (without the softbox) better than this one. This reminds me of what you get with the headlamp on, and no scene lights at all. Everything is lit too evenly. (I don't think I have a very discriminating eye yet...) : /
In any case, I posted in another thread about a page on Nvidia's site with a short video about the capabilities of the Iray engine. Scroll down to the section on Compositing Elements and Light Path Expressions. Very cool!
http://www.nvidia-arc.com/products/iray/rendering.html
In Studio, under render settings, there is a setting called "Alpha". You might be able to tweek the transmission of background objects there.
This render engine is so complicated! It's going to take a LONG time to unlock it's secrets!
And about the environment intensity slider...I agree! If a setting is non-functional, it should be greyed out and unresponsive, or unavailable. Maybe the fact that it is available means we just don't know how to use it. I haven't played with it at all yet.
You said you used a softbox to light the model's back. Any way to set "cast shadows" to off, or position the light so it is blocked by the model and doesn't shine on objects so you get unwanted reflections?
Just some quick thoughts...
Looking forward to seeing your solutions / workarounds.
Heh, I don't think I have a good eye for imaging yet either... I'm just having to go on what I think looks nice. The problem is that I'm one of these awkward people who's trying to create a comic, rather than just making individual, unrelated images. So this limits what I can do in my scenes. The lights have to be setup so that I can move the figures around and keep at least roughly the same lighting setup no matter where they are in the room or what angle I'm shooting from. If I changed the lights every time they moved, or added lights that have no physical source in the scene then it'd look stupid (to me anyway). That kind of thing really bothers me in digital comics.
The simple answer to this would be to have lots of light sources in the room, like wall lamps, skylights etc but what I'm finding is that the conflicting shadows this causes look pretty horrible because they don't blend very well into each other. And as far as I'm aware you can't switch off shadows on a photometric light, because they are supposed to be photorealistic.
Maybe I'm just expecting too much from Iray...
Thanks for the nvidia link, although I didn't really understand most of what they're going on about. I think thats probably a little too advanced for me right now.
If I come up with any solutions, I promise I'll post them here. But don't hold your breath! ;)
Rendering takes longer in "a room" environment because the light rays bounce around forever within the "room". Make sure you set to finite.
Instead of adding another light, why not just put up a primaries behind her to bounce light back on her (like a person holding a bounce board?).
Environment slider DOES work. Best settings are usually set to .2 - .4. Perhaps it doesn't work the way you think it does?
Thanks for the suggestion. I'm not sure what you mean by 'primaries' - do you mean a primitive? I know that methods like adding a reflector behind the subject, or a softbox etc work fine for individual images but I'm trying to avoid the 'cheat' because when I move the camera to point in another direction I'll have to remove that reflector/softbox which will change the lighting in the room.
Perhaps so... Using Scene Only mode I tried rendering that same image again, once with Environment Intensity at 0.2 and once at 1000000. Both images came out absolutely identical. So what am I doing wrong?
What I thought I understood was that Environment Intensity is delivered outdoors by the Iray dome. Therefore, if you have a completely sealed room and use Scene Only mode I don't see how it does anything.
You need an environment map loaded in for the env. intensity to work.
Also loading an environment map will help with the 'too dark' corners in a single light room.
I would say you are missing your environment, and your actual props aren't bouncing light properly to get the 'backside' of things lit the way you want.
And as pointed out earlier in thread - photographers have to 'cheat' to get their lighting right... We do too! Don't be afraid to position things off screen to get your vision a reality.
Some things are about the journey, and some things are about the destination. In this case, its the destination. You've got an idea of how you want it to look, so worry about the final appearance instead of what it took to get it. Ever watch mythbusters? They first figure out if its 'realistic' or not, and then they see how far they gotta go before it IS real... ( you know, explosions and hollywood stunts etc! )
So..that would mean it's primary use is in outdoor renders?
As I understand it for this project, there is supposed to be no light coming in from outside the room. It's either dark outside, or a completely enclosed room with no light coming in from doors or windows.
Makes for interesting work-arounds!
you set the environment map ( env mode should have 'dome' in it if you want to use the dome ), and then you pick dome mode. your options are as follows:
infinite sphere ( w/ or w/o ground ) ( outdoor / sky scenes )
finite sphere ( w/ or w/o ground ) ( havent played w/ it yet .. can't tell you anything about this one )
finite box ( w/ or w/o ground ) ( perfect for indoor scenes )
you can load an 'indoor' environment map ( that has no light sources in it, just colors or bounce ... even a gray blurred image will give you a good amount of 'fake bounced light' and then you play with the intensity from there.
and I just want to say unless you are completely SEALED in ( where even oxygen can't come in ), you should have residual light from SOMEWHERE even indoors. I think the only place you can find real 'pitch black' is in an actual CAVE underground. ( now that is some black black darkness ) Perhaps a moonless night in the middle of the sahara desert too... but I can't vouch for that because I've only been in an underground cave ;)
Thanks for the tips. Yeah its slowly dawning on me that I'll have no choice but to cheat. Its a bit depressing, because I thought Iray was going to mean that wasn't necessary anymore. But hey-ho!
Are we all talking about the same feature when we say "Environment Intensity"? Because the setting I'm talking about (located in the Environment section of Render Settings) doesn't need an environment map to work. It'll work fine with or without the map in "Dome and Scene" "Dome Only" and "Sun-Sky" modes only. It works either outdoors, or indoors if theres a break in the room 'box' somewhere.
But it doesn't work at all in "Scene Only" mode in my DS (unless I'm doing something very wrong) and theres no environment map option there either. And if you've set your scene in a closed room with no windows it does not impact upon the scene at all no matter what environment mode you choose.
If this isn't correct could someone please illuminate me (pardon the pun) as to where I'm going wrong? I'd be very interested to see a screenshot of an indoor scene where there are no windows and environment intensity is the only light showing.
* Note I'm not talking about HDRIs here. I'm talking solid geometry indoor sets. Basically a solid cube primitive around your character.
I'm also learning the ins and outs of domes and enviro maps. Do enviro maps work on interiors? I just thought they acted as a dome (a sky) for exterior shots.
The way I understood it was that you can load an HDRI into the environment map when the dome is switched on and that can give you your "set", if you like. So the HDRI can be either an outdoor scene or an indoor scene. With this method environment intensity will absolutely work fine because the intensity is coming from the dome and its the dome you loaded the HDRI into.
However, if you use a solid box primitive set like I am, you can't even see the Iray dome because its blocked by the set, so environment intensity will not penetrate it either. Its the exact same reason why skydomes don't work anymore.
That was my understanding and its what I've always encountered when rendering.
Although I'm beginning to wonder now if my DS might not be working right and I need to submit a support ticket...
Doing some tests right now so I can provide some more experience.
I have 6 hi rez squares w/ iray shaders on them ( stucco and wood ) and a single candle light attached. Scene only lights, no env. map. Will post my results when they are done ;)
I was about to comment on that...to properly 'bounce' an item needs to have a surface that Iray will 'see' as a proper Iray material. So it needs at the minimum, the Iray Uber.
Cool, thank you :) Can you include a shot of your environment settings as well please, so that I can see where mine differ?
tl155180, something you may not be taking into account is the volume of space that would realistically be lit well by a single light. The larger the space the more the light decays between the source and the walls and then back again. By nature most "rooms" we use are larger than standard because of needing space for camera placement.
I did a quickly with what amounts to a hundred watt bulb in a 16x16 room. I guesstimated the room height so it is about 10 foot which is a bit high for a modern room. Walls are .54/.54/.54 (light gray) and I set the tone mapping to a 400 iso fstop 3.
Mode set to Dome and Scene. Set to Finite Sphere. Draw Dome On. Visualize Finite Dome on. Enviro Intensity at 1. And the stock Ruins 500 HDR loaded. and still no sky out the window.
Are all "sky domes" in Iray these invisible HDRI's?
Hi dkutzera - I think you posted in the wrong thread by accident, but I know what you're talking about so its ok :)
The Ruins 500 HDR is for lighting only - its not meant for image. Thats why you're getting a blurred image on the dome. Remove it from the environment map and you should see blue sky instead.