iRay Lighting for Interiors?
inquire
Posts: 2,204
I've used the default dome, with and without showing it, and other "backgrounds" that are exterior, and I can get good lighting and fast rendering. But if I try an interior scene, even if I have one wall removed and a large window at the back, it's too dark. Adding spots, however low in intensity, produces harsh shadows. There doesn't seem to be a way to turn off shadows. The same thing can be said for my experience with a Distant Light, even if I keep it at 0.25 % or even at 0.12%. I've tried adjusting the spots with the lumens values, too. No luck with that. What should I do for lighting an interior scene, or even a partially shaded scene in which there are three walls, a floor, but no ceiling? Additionally, I've turned off the specular light in the spots, setting a spot to "Diffuse Only" for the light. I can get a light value that I like. However, the shadows really bother me. They are much too harsh.
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Comments
Use the camera settings in Tone Mapping. They work just the same as a camera the less light then increase the ISO/lower the f/stop and/or lower the shutter speed.
If you want to use an HDRI then use Finite Box and lower Dome Height to the height of the room ceiling.
OK. Those sound like good tips. I will try them. I have experimented with "camera settings" (as these aren't real cameras) with LUX. That doesn't mean I know what I'm doing!
They are, intentionally, close enough that a basic book on digital photography will help figure it out.
Where is "Finite Box"?
Render Settings/Environment/Dome Mode You can have it with ground or without. With gives you shadows on the ground plane.
To get rid of harsh shadows with spots (everypne repeat after me):
Increase The Emitter Size of the Spot.
Go to the spotlight parameters pane. Under Light Geometry change to Disc or Rectangle. Then set a Width and Height for the emitter. Anything over 15 to 20 (cm) starts to soften shadows. A 100x100 emitter is a 3 foot square soft box, and behaves just like a real photographer's soft box.
Remember that in Iray lights take on real physical properties, so like in the real world, the size/spread of the beam determines the shadow edge. As mjc points out, a good entry-level book on photography really helps here.
Just as a BTW, adjusting light intensities is not how you control shadow edges. You posed two different problems: 1) Harsh shadows with spotlights and 2) An (overall) dark scene with an HDR dome. These have two different solutions.
Even with a decent indoor HDR, and proper camera (ISO/f-stop/shutter) settings, supplemental lights are still often needed to give good tonal range. This is especially true of the freebie HDRs, which have a fairly flat dynamic range, without the good highlights that provide realistic tones. For indoor HDRs, if adjusting the camera settings still gives a flat scene, just try another HDR.
Also try rotating the dome so that the "light sources" contained in the HDR favorably fall on your subject. In the Iray Render tab, choose Environment, and go down the list for Dome Rotation. Correctly defined HDRs *usually* have the light source in the north, or 0 degrees. That means the main light source is behind the subject, opposite of where you usually want it. Note that the "Ruins" HDR that comes with Studio doesn't behave this way. The main ligjht source comes from the east, so to get modeled light, change the rotation to between 40 and about 110 degrees.
Ditto what Tobor said - increase the size of the light geometry. For some reason, when you create a new light, it defaults to Point, which is the worst geometry of them all. I generally use disc or rectangle, sized between 50 - 100.
Re Tone Mapping - In my experience, a scene with 5-6 lights needs an ISO of 1200 - 2400 to get a reasonable level of exposure.
Interior lighting is definitely trickier to get right. I only began using HDRIs 2 days ago, and I suddenly realised why everyone loves Iray. Practically anything looks good with a HDRI in an outdoor scene. But if you want to go indoors, you really have to master lights. And in the end, it's well worth the trouble.
Btw, don't forget panels. I often use several DS primitive planes as panel lights, and activate the Emissive property in the shader*. To position the planes properly, I parent each one to a camera, and look through the camera view, then adjust it, and the plane follows.
* Don't forget to turn off Two-sided in the shader, or renders will take much longer.
What! ISO of 1200-2400 is way too high even for a dark interior. Drop the shutter speed and the F/Stop instead and us 200-800 at the most.
It amounts to the same thing. Or I could up the EV instead. I just prefer to work with one variable - ISO. It's not like it's going to be grainier.
I like playing with time...it's not like the scene is going to 'move' on you, so you are free to use as slow a shutter as you want.
This part isn't clear to me. Panels I get. Activate the Emissive property? Is that in the Surfaces tab? Can't find it. Is it in the Render settings? Also, turning off two-sided in the shader: where is that, again? Surfaces tab? I'd try it if I knew what you meant.
IMO, avoid using surfaces as principle scene light sources. I know people have been talking about it here, because other PBR renderers use them heavily. But nVidia recommends against it in their documentation, for performance reasons, and they provide plenty of other native objects that are specifically optimized as light sources. Save the emissive setting for when you need an object to light up (TV screen, sci-fi control panel, etc.), not to provide the lighting for your scene.
For future reference, to make an object emissive, select its surface in the Surfaces tab. Go to the Uber Iray shaders in your Content folder, and find the one that says Emissive. Apply it. This zeros out all the other settings (very important) and "activates" the emissive property simply by changing its emission color from all-black. You can dial in the color you want, and specify the strength of the light.
If you want a broad light source, use a spot light, and change its emitter from Point to Disc or Rectangle. Then alter the width and height of the emitter. You can make gigantic light panels this way -- the ,measurements are in centimeters, so a 200 by 200 emitter is over six feet square (or diameter). Iray is more efficient when using its internally-defined light sources. Two other benefits: 1) you can view the scene "through" the light without the use of auxilliary cameras, and 2) you can very easily hide the emitter from the renderer by selecting this property for the spotlight.
@Tobor "Increase The Emitter Size of the Spot."
This is a premium tip!!!!
I am getting a lot of help from these suggestions. So thanks, everyone. Yes, I have tried increasing the size of the spot (been changing it to rectangle).
Just as another thought, I do have Reality, and it supplies Mesh lights. Do they work with iRay, and, if so, as well as the spots, or should I forget the Reality Mesh lights.
About changing the rotation to between 40 and 110 degrees, you are writing about the "Ruins" HDR that comes with Studio, correct?
For the "correctly defined HDRs," would I rotate to about 300 degrees, or rotate not at all, or what?
I'm not sure which HDRs you mean the rotation to apply to. For a single figure, I rotated the "Ruins" HDR 55 degrees, cutting it about half way between your recommended 40 to 110 degrees. Seems to give too much light to me. I think I'll turn it back down (just in this case) and render again, just to better understand what is happening.
Rotating the dome is a personal preferance thing. It's where YOU want the strongest light to come from, so there's no real right/wrong...and it doesn't really matter what the original alignment is, either. Doing the rotation on the dome/light is a lot easier than rotating all the scene elements to get them the way you want the light to fall.
I see the first benefit. For number 2, hiding the emitter from the renderer, I selected that in the Parameters Tab, under Display, and chose "Visible in Render," which I turned to "Off." Now, the spotlight goes off in the Preview. Will the light nevertheless render when the scene in rendered?
Actually I didn't "recommend" 40-100 degrees, just noted that these rotations would give you an off-from-center modelled light, either to the right or left of the character. Depending on your goals for the scene, this might be what you want, or it might not. You could turn the dome to provide more of a side rim light, or a back light, or something else. That's completely up to you. The point is, you need to experiment on a per-HDR basis.
You missed the option that says Render Emitter. That's the one you want. It's not under Display, but Light.
If you want mesh lights, create them using the plane primitive in D|S. Apply the Emissions Iray shader, then adjust color and intensity. But, in following nVidia's recommendation, avoid this for lights that you can just as easily create using D|S spotlights. The "shaped" emitter feature of these spotlights directly couples with the built-in light types understood by Iray. All the spot light variations -- point, disc, rectangle, etc. -- are defined in the Iray application itself. So, for Iray you don't need mesh lights to produce general illumination, because as others have noted -- and discussed in nVidia's documentation -- they take longer to render. Save the mesh light feature for recreating practical light fixtures, such as fluorescent panels, or light bulbs, or glowing TVs, or whatever.