Using iray environment lights "indoors"
There are some really lovely environment light sets available for iray. When used with an isolated figure, they look beautiful, but once you add a room set, the walls tend to obscure a great deal of the lights. There are only so many walls you can delete without affecting your scene.
Does anyone have any helpful suggestions about how to use environment lights in a room? It would be nice if somehow walls could be made transparent to lights, but still visible in renders (though that may be a contradiction in terms!)
Thanks
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iray is an unbiased renderer, so you can't really exclude geometry from lighting/shadowing like you could in 3dl. My questions would be - are you really hell bent on using hdri's to light your interiors, or are you open to other methods? There are several ways to make interiors converge faster, but it really depends on the overall effect you are trying to acheive. You have mesh lights, light portals, ghost lights and photometrics, all with their pro's and con's. A well lit room will mimic the effect of an interior HDRI, it just depends on how much cheating you want to do in order to cut back on render time.
I have an Iray light rig I use often to light interiors. Like everything in Daz it requires tweaking because everyone renders in a unique way. If when I load it into a scene and it doesn't quite fit, I'll use the parameters dial to shrink or expand it. Other times, I'll have to move the lights individually so there isn't "splash" on the wall or furniture. Another trick might be to select the environment it self and see if you can expand it. Some environments let you do that, some don't so it really is case specific. I find it can be helpful but you do have to watch out for distortion especially when it comes to door and windows.
Well.. I guess the reason I like enviro (or lighting sets that include enviro) is that I totally suck at building lighting from scratch. So I guess I like to cheat! So I know what you will say.. learn to light properly yourself! ;)
BTW render time is not a problem as I have a GeForce TITAN X (which renders even huge scenes in almost no time)
That's interesting. So are you saying I should shrink the environment sphere so it fits inside the room? I had never thought of that!
I also use Titan x's, but interiors can still take a while to converge if the scene doesn't have enough light to play with. If you want completely natural indoor lighting via windows, simply crank up the environment intensity (render tab) and reduce the tonemapping value until you get the desired effect. You can use light portals which is an optional mode under the photometric spotlights. Place them over windows so iray knows where the light sources are. If you are having problems getting the scene to converge, you can use mesh lights or ghost lights to add more direct lighting to the scene.
Reducing the overall Hdri size is hit and miss, since its obviously a sphere shape, which means you'll end up with circular artifacts on the floor and walls.
If you are looking to light the scene via lamps (or even windows), simply using emissives is a good option. If you dont want to tinker with your own emissive values, DzFire did a great pack of presets here: https://www.daz3d.com/real-lights-for-daz-studio-iray.
You can, with enough trial and error, do it, though...but usually the time involved is not short. Just for 'fun', I tried it one day...and the time taken to size the HDRI was much longer than the render took, with other lighting. Something like 3 hrs of trying to get the HDRI vs a one hour render.
ok thanks peeps. I shall experiment
Check out this thread: http://www.daz3d.com/forums/discussion/110771/natural-iray-lighning-for-rooms#latest
it maybe gives you some ideas.
great! thanks friend :)
Wow, that sounds very interesting.
But how do you mean: "over windows"?
Or where to position?
I haven't used these very extensively, so i can't really say how well they work. Never the less, Here's what to do -
Add a spotlight to the scene - Go to the parameters tab - change the light geometry mode to Rectangle - Now enable Light Portal.
Now, move your spotlight (stay inside the room) to the front of a window. In the parameters tab, change the height and width, so the visible rectangular outline covers the size of the window. You also need to enable caustic sampler in the optimization group (render tab).
Image attached.
Ah, I see.
This is very similar to what I did for 3DL. There I placed an Uber Area in the windows to imitate the diffuse daylight entering through the windows.
Is it necessary to adjust the intensities, if you have several windows with individual areas? Do I have to calculate the intensity related to the cm² of the window areas?
Talking about photorealism (for iRay) means: A big window gives much light, a small window only a little.
Or is it regulated by iRay itself?
Hm,
I tried this - nothing.
The room stays dark.
Caustic Sampler = ON, Portal = ON. Rectangle positioned.
Strange - since Portal = ON there're no parameters for color and intensity any more.
I tried with SunSky, with Scene Only. - Nothing.
No Idea how it works.
I dont think they help with overall illumination, i think they just help the scene converge faster. If you want my advice, ditch them and use ghost lights. Ghost lights are invisible mesh lights that illuminate areas but dont show up in scene or in reflections. Here's what you do -
Load a scene with a window obviously - Create, Primitive, plane - Resize the plane and place it over your window - Now go to the planes surface in the surfaces tab.
Ghost Materia (Iray uber shader)l:
Emission color: 1.00,1.00,1.00
Emission Temperature: 7200 (K)
Luminance: 100 (This controls the overall intensity, so feel free to play with it)
Luminance Units: kcd/m^2 (Important)
Cutout Opacity: 0.001 (Very important, this will make the plane invisible)
Now you should have the mesh light positioned, and emitting light from the shader above. Go into Iray interactive mode, and change the Luminance value until you hit your sweet spot. This is for a daylight scene, but if you want to do a room that is lit by and overhead bulb - you can place the plane above the light, resize it to cover the ceiling, and lower the intensity. Now you can have the bulb doing the lions share of direct lighting, but the overhead ghost light will helping the scene converge faster.
I hope that all made sense, let me know if you get stuck. These single poly planes are incredibly cheap to render, and you dont even need to hide them out of shot.
*Edit: Don't place them outside the windows either, place them inside. They wont be visible, so it wont be an issue. If you have them outside of the window, they will be emitting through refractive glass, and effecting render time further.
I've just written a tutorial on ghost lights here: Link If anyone's interested. There's comparison shots and some image guides.
Hi KindredArts,
I don't know what I'm doing wrong, but using portal lights renders slower, compared to the normal setup.
Using Portal Light (incl. Caustic Sampler):
18.4% after 1 hour
normal setup (of cause without Caustic Sampler):
25.2% after 1 hour.
Attached you'll find the setup (screenshot). A little sunlight enters the room too.
Portals are not usually necessary, and may be counter-productrive. Iray supposedly already does a good job of working out where the rays are needed without using a portal.
As richard said, portals are a bit of an odd beast, and i really don't know anyone who uses them. They are however touted as the interior lighting fix, so perhaps we just aren't using them the right way. The issue you're having with that room, is that there is simply not enough light in there, which is working your rig much harder. If you follow the tutorial i posted above, you'll have a lot more luck. You can still get a natural look by emitting low energy ghost lights into the scene, whilst converging faster. In fact, that is macleans bungalow right? I have that pack. I'll post my set up in a bit and you can copy it.
Here you go, the render finished 100% in 7 minutes using ghost planes. I cobbled it together really quickly to demonstrate, but with a bit of tweaking you can get it exactly how you want it. I just shoved Two ghost lights in front of the windows to boost the lighting from the hdri.
OK, I know.
But this isn't what I wanted to do.
There is the natural light entering the room. I really like how iRay shows the photorealistic reality. It's just our internal picture processing system (our brain) that shows the interior way brighter as it is in real. Do a photograph and compare it with what you think to see.
The example you show may be suitable for render, but it is not realistic.
I know, in those action games or videos real realism doesn't matter. I used this trick with the additional UALs, too. But only for 3DL. And even there you needed a high shading rate for a proper resolution, which even in 3DL needed an eternity to render.
So I'm eager to learn about methods to speed up the render without loosing realism.
Cause there a two limiting conditions:
1. I don't own those expensive GPU cards,
2. most of my sets (in iRay) would kill the available GPU cards' capacities. So anyhow they were useless.
I hoped the portal lights would be helpful ...
Half way down this page explains how Portal Lights can be used.
http://download.autodesk.com/us/maya/2011help/mr/shaders/architectural/arch_sunsky.html
If you want to see more light in the back of the room then turn down the Environment light and set the Tone Mapping to compensate making the rear lighter. It is a balancing act between the amount of light coming through the window and the amount entering the camera, which is what our brains do with the image entering our eyes :) Another way is to make the ceiling, if it is a separate surface, emissive at a very low setting so that it throws a general background light across the whole scene, again using Tone Mapping to compensate.
Hi Fishtales,
thank you.
Most of what they describe, I can't find it in the iray parameters.
One thing I'm missing in these descriptions:
How narrow to the glass pane of the window must the portal light be placed? I tried it really near to the window glass with the result, that most part of the spot body was outside. If I placed it that way, that the body of the spot was inside too, it was almost 15cm inside the room - away from the real window.
Perhaps it depends on this condition that I couldn't see any positive affect to the render time.
Should it really have?
Those hints are well known to me.
As I stated, I didn't want to get more light intensity into the room - I only wanted to speed up the render.
But adding additional light sources, either photometric or meshlights only dramatically increase render times.
If I wanted to have the backside of the room more bright, I only needed to increase the gamme - not forgetting to carefully increase the color contrast, too.
But it can't change the indirect lit space in the scene. And the amount of indirect lighted areas determins 95% of the render time.
Honest: Adding additional lights don't change the general situation. Every lightsource (photometric and mesh) as long as they are not a point-lights, do indirect lighting.
So: Nothing won related to render time. I already experienced this in a lot of my scenes.
Render speed is a function of pixel convergence; more rapid pixel convergence occurs when there are more samples per pixel, and the way to get more samples per pixel is to boost the level of light.
Indirect light is when the light source produces an ambience rather than direct illumination of a subject. A light that is cast to a wall, which then produces the light for a scene, would be indirect. Light shining directly on a subject is direct. It is incorrect to say that every lightsource (point lights or not) are indirect. They may differ if they are diffuse (in the case of mesh lights without a profile). Diffuse light will take a little longer to render, especially when the mesh has many facets, because of the exitance calculations. This is why it's a good idea to use coarse geometries for emissive surfaces whenever you can.
You are correct that any indirect/underlit areas contribute to the largest percentage of render time (as a function of sample collection), but there's no rule that says you can't use hidden light sources. The old paint masters did this frequently. They also do it in movies and TV as general procedure.
You mentioned changing gamma, which is a tone mapping function. Just like changing the f/stop or shutter speed on a camera doesn't change the actual light in the scene, tone mapping doesn't alter the light levels in an Iray scene. Because the light levels are unchanged, rendering speed remains largely the same. The way to increase brightness in a scene is to select reasonable tone mapping settings, and add more light.
Light portals (the official term Iray uses) will not make average renders faster. They are used for very problematic scenes where the indirect illumination causes such a low progress of ray samples that it's not otherwise cost effective to render the scene. The scene will still take time, especially since the mechanism is coupled with the caustic sampler, which adds tons of overhead calculations.
From the Iray technical documentation:
Using light portals should not change the rendering result, only convergence speed. However, it should be stated that they do not always help, in fact they can cause lower performance if placed incorrectly. For an architectural scene a rule of thumb for using portals is:
A significant amount of illumination comes through the windows.
The illumination coming through the windows is not dominated by direct sun light or other very bright regions in the environment.
The windows are relatively small.
The caustic sampler is enabled
I usually convert anything that can be a light source in a room with http://www.daz3d.com/real-lights-for-daz-studio-iray even if it''s not in the picture and if there's not already a ceiling light I create a 1 foot across by 2 inch deep cylinder with a real-light shader. I find it doesn't slow very much and gets rid of the blotchiness. Of course if you trying for a dark room you'll have to turn up the number for passes/render time. Also turn on some kind of environment lights if I have windows that are large enough.
Did I say this?
No!
Every light source having a distinct area (so not for pointlight like sources) has a dramaitic influence on prolonging the render time the same as indirect lighted areas have their contribution on it.
You may have a different oppinion, but if you don't believe, make your own experiment:
Use a closed room, position several spotlights on the ceiling and compare the render times when you make the spotlight's area way larger at same light output.
You'll see.
Yes, you did say it:
"Every lightsource (photometric and mesh) as long as they are not a point-lights, do indirect lighting"
Maybe you're suggesting that in addition to direct illumination, light sources contribute indirect light to the total scene, but that is irrelevant. As I've said, render speed is a function of iterative convergence. Convergence is based on samples to pixels. When it's only indirect light to these pixels, there are fewer samples, and therefore slower convergence. It's not at all complicated.
Your experience with the spotlight merely shows casting light of a certain luminance into a larger area, which means less incident light per surface area on the subject. You're back to less samples, and slower convergence. If you had an incident light meter in the scene you'd see this immediately. Just as you would in the real world, you counter this by increasing the light output by a reciprocal value.
I have the same problem. The light portal does nothing.
Why would DAZ release a light portal feature but not provide any documentation on how to get it to work or even show an example of it working?
If you create a plane primitive, make sure that the orientation is "positive" not "Negative". Some of the negative planes will, for whatever reason, not emmit light.
The sun-sky is the only light source in the scene. I was hoping the light portal would help the sun-sky light fill the room, but the light portal does nothing.
I haven't played much with light portals, to be honest. I usually use a distant light in the sun-sky setting to direct the sumnlight as I want, and then use mesh lights to light up other parts of the room, if neccessary.