Why is lighting a scene so difficult in Iray?
lou618_2b45855fe7
Posts: 65
in The Commons
What light should I be using to light a simple scene? You would think one new linear point light would be enough to light a small room, but apparantly its rocket science in Iray. I need some help because this is exhausting.
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Grab this
https://www.renderosity.com/freestuff/items/87831
best free light set ever
It has premade light shapes, square, curved, round that have a camera fixed to them. Use these to light a room.
Switch your view to the light's camera(they are clearly marked in the view dropdown menu) and you can point it by moving the camera around.
There is also a dome with lots different sections that are lights.There are many presets to make it easy to get the dome lit up in every conceivable way, including the entire thing.
A single linear point light is like using a cigarette lighter to light up a cave. You can do it, but you are going to need a lot of them.
When you start something new it's all a big mystery. It feels like it's an impossibility to get it to work. Everything seems unimaginably complicated. We expect everything to work instantly and without thinking - like turning on a light switch. I avoided iRay for years because it felt like struggling with a monster in a dark void. But you know what - it's EASY PEASY! Now I throw those iRay lights around like rice at a wedding. I can light anything and make it look like a $200,000,000 movie. Forget about 3Delight and Poser and real world lights.
You learn to use iRay lights by fooling around with them. You discover how to use them. This is the single most valuable light I've bought - and I've bought a LOT of light sets: https://www.daz3d.com/iray-ghost-light-kit
It's like a sheet of plywood - that you can make any height or width. One side of it glows, throwing a beautiful soft all encompassing light on what ever you face it to. If you want to light a room - NO MATTER what size the room - take that ghost light panel and stretch it's width and height so that it's the size of one of the walls. Face it into the room with the little arrow attached to it. There's clickable settings to change the color of the light to match different times of day, and other common lights we have in real life. There's clickable settings to adjust the brightness from dim to extremely bright. What ever you point the ghost light at - lights up and looks natural.
Take the ghost light and reduce the size to 1 foot by 1 foot and place it a foot away from the face of any character, and voila! Perfect portrait lighting.
Change the dimenstions of the ghost light so that it fits exactly inside the frame of a window, and like magic, you have natural looking outdoor light flooding the room.
You can stick these ghost lights anywhere in any scene to light up anything. Just change the size of the panel, change the brightness, change the angle and position - stick 6 of them in the middle of a room pointing at different things - and then just click, and the light panels disappear in the scene and you get LIGHT.
It's perfect for indoor lighting, day or night. There are other products that are more practical for lighting up outdoor landscapes. But you can use the ghost lights outdoors as fill lights to illuminate characters.
You can turn the ghost lights around in the windows of a house so they are facing outwards, and all your windows will glow naturally in the dark night.
I've lit everything from huge indoor medieval castle rooms, to garages, to the inside of refridgerators.
Try it. If you don't like it, you can return it. It's SUPER EASY to learn to use, and gives supurb results.
Totally get a book on film lighting or look at youtube videos, Blender Guru has a wonderful lighting video on youtube. Even though it's for Blender, the principals are exactly the same as there is zero difference between real world lighting and iray lighting. I've been making films for twenty years now and when I found out about Daz, lighting took all of five minutes to figure out simply because it was the same as what I'd been doing for years. It was more a matter of adjusting to the luminance than how to actually light the scene.
Personally, I don't use the linear point lights or spotlights, I tend to make a plane or sphere and turn it into an emissive texture and use that to light, or mesh lights from like dimension theory.
Iray does not have linear point lights. Because Iray simulate lights based on real world physics, lights follow the inverse-square law. https://en.wikipedia.org/wiki/Inverse-square_law#Light_and_other_electromagnetic_radiation
You can light a room with a single light if you want, but you would want to think of how a room would be lit in the real world with just one light. Most photography and filming is not done with just one light, which is why if you want to light your scene light a studio or movie set, you would want to learn the basics of how they do lighting so you can follow the principals when setting up your own lighting with Iray. You will also find that a side effect of setting up lights similar to how it is done professionally can also improve the performance of the render, allowing you to finish a render with less iterations and less noise faster.
Lighting in Iray is complicated due to a lack of good end user documentation and best practices are tribal knowledge which is unfortunatly also full of bad advice or users parroting things that are not accurate. Also, lights in Iray are greatly impacted by settings in the tone mapper in ways that are not intuiative or obvious which certainly does not help a new user.
Is it rocket science? No, but it is science and mathematics complicated by a cumbersome user experience where control over lights are spread across different parts of the user interface in a confusing way.
I respectfully have to disagree with the above 2 posts. I was a union grip on feature films and there were literally hundreds of lights in a lot of scenes. If you try to use iRay lights like real lights used in movies you will overcomplicate things. You can do it. You can match the way each light is used on a movie set. But it's very very complicated and time consuming. I know how to do it - but there's no way I'm going to go through that hell of the physics of light to make a render. We would set up lights for 10 hours and they would get 5 seconds of film. Then we'd move all the lights for another 10 hours and they'd get 2 minutes of film. Lighting a render should be super fast and easy. Not agonizingly complicated.
There are products in the DAZ store that look like regular table lamps, floor lamps, ceiling lamps, recessed lighting - you stick one in your scene and it looks just like a real lamp is lighting up the couch.
I personally hate lights other than as highlights; I find them computationally wasteful and inelegant. I would also suggest that you look into HDRI's also.
One need not simulate every light bulb, but the general setup. A single photometric Iray light with the geometry set to a rectangle can easily be used like a softbox. Using actual lamp props for lighting a scene is usually going to increase your render time as emissive geomtry is less efficient than Iray lights or HDRIs. If the lamp isn't part of the actual rendered image I always turn off the emmisive surfaces and use photometric Iray lights. Some PA sets go overboard with emmisive surfaces and this change can bring render times and noise down significantly.
@Fauvist, I totally agree on using ghost lights. It's the only way to light some interior scenes so they'll render in less than geologic time. I'll often use an HDRI, one or two ghost lights and maybe one spotlight. I prefer to keep things simple too, as I am not an expert in lighting.
Here's a free ghost light shader. Just make a plane primitive and apply shader, then adjust the light.
https://www.sharecg.com/v/87021/browse/7/material-and-shader/simple-iray-ghostlights-shader
There are also various light probe sets, some free, that let you see what the lighting will do. Since some things do not show up properly in the viewport, even in iRay mode, I'll often start a render to a new window, and cancel after a few iterations. iRay preview mode is good for aiming lights, especially with the light probes in the scene. Render to new window makes everything look right.
I guess it depends on what you want to achieve and the time you have. Sure, you have the option to click on a set and have it perfect in ten seconds and have a render, or you have the option to really spend the time and get every nuance exactly how you want it. There's no right or wrong answer or way to do it. Sometimes I do use light sets, but most times I feel far more creative when I treat my shot like when I'm on set and I'm setting up bounce boards, flags, cookies, etcetera in my 3D scenes along with as many lights as I feel the shot needs. But it also takes me all of ten minutes to do a simple, run of the mill 3 point light setup on a character in Daz, it's not nearly as long as when I'm setting up a shot in real life, but the concept is the same. The other day I spent five hours lighting a shot that I wasn't even animating, it was just something fun to do because I needed to do something creative. So it all comes down to whatever floats your boat, but if you understand the concepts of lighting, it translates into Daz perfectly.
Before I explain my comment, a clarification should be made: HDRI's are both light sources (light probe) and sometimes backdrops. For example, products like https://www.daz3d.com/elianeck-iray-warm-light or https://www.daz3d.com/sy-fast-lights-iray-hdrs or https://www.daz3d.com/iradiance-light-probe-hdr-lighting-for-iray-expansion-3 are very small synthetic images and are lightning fast. There are some large HDRI's which people use to create detailed backdrops but that isn't required to light a scene.
Spotlights and point lights have that inverse square problem and create too much light bounce which adds to render time.
Here is a render I did that uses an HDRI, no lights and a primitive as a backdrop rendered all by just GPU:
ONE light. The huge dark brown "study" is lighted by ONE ghost light. Miami Beach is lighted by the sky.
The problem with Iray lighting is Daz Studio itself. The default values that Daz gives you when you create a new light are pitiful. In many scenes lights with these values have no impact whatsoever on the scene. You are basically trying to light a big room with something that might be about as powerful as a candle. The default measurement is super tiny, and you sometimes need millions of these units to actually create a visible light. With numbers like this, is it any wonder that new people have trouble wrapping their head around it?
Come on, most people are not professional photographers or gaffers. And even then, they still have to figure out how to use Iray. Not all the Iray values line up with reality, a perfect example is depth of field on cameras. In Daz the numbers you can get with DOF can be basically impossible in reality. Instead of using numbers, what you do is use a second camera (or the default perspective camera) to move away from the scene to get an overview, select the camera you are using to take the image, and you will see the DOF box in your scene. By simply looking at the DOF box you can adjust the dials to make the DOF exactly what you want it to be. This trick makes DOF a million times easier.
This can extend to the tone mapping settings, sometimes your desired results may use tone mapping numbers that wouldn't make as much sense in reality.
The best thing to do is to pick up some light sets to use as starters. Use these lights to get a feel for what may work. There are a LOT of things can effect how a render is lit. You have the lights in the scene, you have HDRI lights, you have shutter speed, and you have tone mapping and white point balance. Every single on of these all effect light. Tone mapping and shutter speed can be your friend with indoor lighting.
Another note, movie style lighting is not realistic, as any gaffer would confirm. They change lights between cuts, which certainly wouldn't happen in real life, and the lights themselves are often hanging in any number of places that just would not exist in reality, not to mention the colors they may use. So making images with Iray you need to decide on how real or Hollywood your renders will be, and you will likely need to compromise a good amount even if you want to do realism.
The reason for that in interior scenes are the default Tone Mapping settings that are set for bright outdoor scenes.
If you try lighting an interior scene with the default Tone Mapping settings, you need to increase the 'Luminous Flux' value of the lights 100 times of 'real world' values.
All you need to do is set the 'cm^2 Factor' to 8-10 and Film ISO to 400 and you can set the 'Luminous Flux' to something realistic.
Not even the PA's seem to be aware of this, which means you have to check any and all included lights in a scene to check if they are set to realistic values or 100 times bigger.
@ Outrider42, Agreed.
That said.
I've taken to using the "watt" instead of the cd^m or lumens scales as I pretty much know what a light with a certain wattage value looks like. and adjust rinmapping for interior scenes using the exposure value setting. As I was a photographer, not professional basis but still reasonably knowledgeable, when I first started working with Iray, I used actual film/aperture and shutter speed settings only to find they didn't work teh same as in the real world. For most daytime outdoor shots I used Kodachrome 64 and indoor shots (without flash) Ektachrome 400. For outdoor night shots I used timed exposures. with Ektachrome 200 or 400. i also push processed film (shooting at a higher ASA rating than the film was rated at) to get night time handheld shots (of course this does have an effect on image quality in certain instances)
Daytime outdoor scenes with Iray are a cinch to light because I use the sun/sky with the Sun Chain as I am not into fiddling around with global coordinates and time of day, month, season,whatever as that is just more complicated than it needs to be. I have found some HDRs to have a cooler "sun" temperature than the Iray sun, and with some, shadows are sometimes too sharp edged and don't diffuse properly with distance. Fortunately there are different cloud and fog effects that work with the Iray sun so I can get varying sky effects without having to resort to composting or using HDRs.
The issue I have is not setting up lights where i need them (crikey I did that with 3DL and some of my lighting rigs were pretty involved) but the fact emissive sources have a major impact on render time. Mesh lights function more like real light emitters (bulbs, tubes, & such and thus are easier to place than in 3DL to get a more realistic looking light source. As I do a lot of dark dystopian cyber future settings, flooding the scene with an HDR or ghost light would ruin the effect. I am after (currently wrestling with this in one scene) so I tend to use more emissive sources which in turn increases render time.
As to "ghost lights" it is not hard to create them using a plane or sphere primitive with opacity set to something like 0.0009. But again this is more of a light box effect. rather than a specific light source or directed light source like an electric torch, searchlight, or vehicle headlamps, though I rarely use them save for just a bit of ambient lighting to suit the scene (like moonlight or the background glow of city lights).
Unlike creating a cinematic setting, I often like to build my scenes in a way as if viewed with the naked eye (as I often did when I still painted) rather than a camera lens with cinematic lighting hence my minimal use of DOF (for which I also set up a secondary camera to check the field box as well). This is where Iray breaks down for me .
Yeah I'd probably do well with a 3090 that has all those cores, a faster processor, and faster memory, but that's a "lotto dream" right now Just finding it disheartening that even with a 12 GB Titan-X I am dealing with long render times that I would almost expect to see with rendering in CPU mode.
3DL seemed so much more simple.
I think the main issue with iRay is the missing control about light bouncing.
That's propably the main reason why indoor scenes are always too dark and you need ghost lights.
In Blender you have much more control over light bouncing.
some basic information might be of use for the OC,
1) when you have your render settings on sun sky only, the lights from the light tap (spot light/ point light) don't do a thing. What you can do is create is primitve (like a plane) and make it emissive, that works very effciently (switch the units to kcd/m^2)
2) the same happens when you have the render settings to dome only, remedy as above
3) the render settings dome and scene and scene only allow for the use of spot lights and point lights, the unit this is set to is Luminous flux (Lumen) and the standart is set to 1500. You can per default add two to three "0" to that number to have it in a ranger that matters
4) HDRIs should generally give you enough light to render in an outside setting, They wont suffcently light a room through the windows. Simple trick, turn the windows into emissives or add some emissive planes right outside the window to give a full blast of light into the room
the rest is experimenting, but there is no need to install a whole army of lights in your scene
Join the new users challenge or read through some of the older new users challenge threads to get a better grasp of the thing
ps: there have been some suggestions to change the exposure settings in the tone mapping tap. that certainly is a possibility and will help lighten up a room, it might lead to longer render times though. Iray works fastest with a lot of light already in the scene
Not my experience.
The OP is not the only one with this frustration. Purchased a bunch of light sets and it seems like any settings other than the brightest are too dark but that can't be right or why have the other settings in there? I know its user error because there are heaps of renders in the gallery using the same lights that look great. Unfortunately the light sets come with very minimal instructions for us noobs and a lot of settings to mess with.
And lets not even get into that Daz often installs part of the set under light presets, part under props, part under scenes.
I've also tried my own setups.... 3 point lighting, 5 point lighting, ghost lights, messing with the dome rotation, dome & scene, scene only, remove ceiling, remove walls, put them back. Especially indoors, if I get enough light so the model looks great then the environment washes out Turn down the environment settings the model looks like somebody is shining a spotlight on them inside a house.
I've watched and read enough tutorials to ave a basic idea what the settings do, doesn't mean I can make them work. Got a bunch of scenes saved that I gave up on because I couldn't light them right.
*screams*
Haha, sorry for the rant, totally understand how the OP feels! Maybe its time to join the newbie challenge as suggested.
I've put together a little tutorial on lighting in my Art Studio thread that you may find...enlightening.
https://www.daz3d.com/forums/discussion/comment/7048791/#Comment_7048791
Reading through this thread I think ya'll realize that for as many users of Iray there are out there, there are equally as many opinons about how to go about lighting with it.
I started out with Iray, so I have no experience with 3DL. I didn't need to "unlearn" any techniques in order to get used to lighting in Iray. That alone, I think, helped me get started. Also, having practical real-world experience with photography helped immensely. The only thing I can say is...find something that works for you. Some folks like mesh lights. I hates them, precious. Some folks rely on ghost lights to light up an indoor scene. Personally...I don't use them all that much except in very specific situations. I've found they can easily leave a scene too evenly lit and monotone if not used carefully. So again, it's all about finding what look you're going for and what works for you. My suggestion? Find some examples of the type of look you're going for, and reach out to the artist (in the gallery here or on DeviantArt, etc)...and ask them what they used. Most will be very forthcoming. I know I am when I get asked. My big secret for indoor scenes? Don't bother trying to light inside a box. Hide them walls! In almost every single piece I do, HDRI is my primary light source. Even with indoor scenes. I say almost because there is no magic lighting formula for every situation. What may work with one scene might not work with another, and so on. It all boils down to what looks you're trying to accomplish, and what tools will help you achieve that look. Then start playing with stuff and experimenting like a mad scientist.
Also...don't forget tone mapping.
I'd also suggest picking up a couple of light sets and then play around with them, deconstructing them to see how they do what they do. That way, you can more easily customize them and better understand what they are doing and why.
As others have said, you do need to adjust tone mapping to get sensible results using scene lights (without ramping up their luminosity values). If you use the iray Drawstyle there is a simple exposure adjustment tool next to the drawstyle button - the +/- icon - which you can click on to activate and then click on a target point in the image to set the exposure.
Note that you do need the Tone Mapper Settings node (from the Create menu, or added when you render or use a PBR preview mode) to get out of the default values.
One other nice toy to light a dark room is the Iray section plane which cuts a virtual "hole" and lets light into a scene... if you "google" the term, you can see examples.
iRay simulates light as captured by a camera, not by your eyes. In a real world situation where you are in a room lit by one light bulb, your brain is performing a lot of processing for you; eg. colour temperature control, bringing out detail in shadow and highlights etc.
Read up on lighting for photography/film - play with the pro mode on your phone's camera; learn what all those settings do (google them). You can also research specific types of photography - real estate interior photography for example. Then it's practice practice practice :)
Edit: reading some of the tonemapping advice... 1500 lumens is approx 100w for an tungsten incandescent bulb. For an interior shot, you'd need something like shutter speed 1/1, f-stop 2.0-2.8 at film speed (ISO) 100.
In a nutshell, f-stop determines the size of the camera aperture (lower numbers equals bigger hole thus more light), shutter speed is how long the hole stays open (longer times equals more light), film ISO is the camera sensor's sensitivity to light (higher numbers equals more sensitive). You do not need to use inflated lumen values - use real world numbers for the given light in your scene. I find that inflated numbers can cause issues with translucency/SSS.
https://en.wikipedia.org/wiki/F-number
https://en.wikipedia.org/wiki/Film_speed#Current_system:_ISO
For me, lighting in IRAY was frustrating at first but it has become a lot of fun.
The way I see it, there's two schools of thought:
A) Learn about real world lighting in phototgraphy and film, or
B) Just throw some stuff at the wall and see what sticks :)
My method is 20% A (I know what a rim light is) and 80% B
Some basics that confused me at the very beginning:
- You control the brightness of the light not by changing its intensity, but by changing the lumen.
(Best leave intensity untouched, I honestly don't know what its function is and I haven't found a good explanation anywhere.)
- If you load a light into the scene (such as a spot light) the lumen is usually way too low by default. First thing, multiply by x10 - x30, then go from there.
- Spot lights and point lights are your friend. Distant lights can be useful sometimes, but they're quite harsh and unless you deliberately want such an effect, there's usually better ways. Linear point lights are not a thing in IRAY, I believe they behave just like normal point lights.
- Turn any surface emissive by making the emissive color anything other than black.
- A closed space will always take much longer to render than an open space. Even a partly closed space already takes quite a bit longer than a truly wide open space. So whenever you can, try to "fake it" by setting up scenes that look closed from all the angles that matter, but are actually open.
Other important subjects to look into:
- HDRI's
- IRAY Section Planes
- Ghost Lights
Good luck!
Have a look here.
https://www.daz3d.com/forums/discussion/59100/using-other-light-sources-in-iray/p1
first all this is great info!
you don't even need fiddle with pro settinbgs on your phone camera you can also just take a shot and then look at the info of what the camera did automatically
for instance, If I take a photo of the back corner of my room, I can then just click the details of the photo and it turns out my camera used a shutter speed of 1/20 an aperture of 1.7, and an ISO of 1250
I plug those values in my render settings, load up a room in daz and just use the sun-sky to light it and...
its a bit over exposed actually. I couldnt find a room in my content library that only had 1 small window. (I live in a cave.)
The same render settings lit by a single point light set to about the strenght of a singlw 60w bulb. Not the most beatuiful render, but absolutely a room lit by just a single point light (and I even lowered the light strength from the defaults)
and now both the sunsky and point light with the default render settings...
honestly I'm surprised its not pitch black.
and if you're wondering why daz doesn't use these settins as default since you can light up a whole room with a point light...
Now that would be a one hell of a first time user experience
and just to caveat, as mentioned by others, this is not the only way to go about things. Sometimes I don't bother and just crank up the luminance of the lights, but in some instances I find it much easier to use realworld values. If i'm doing something where theres sunlight I don't want to have other lights in the scene that end up brighter than the sun. (and it does fulfill OPs request of a room lit by a single point light)