Tips to Speed Up Closed Room Iray Render, please
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I've come to really like Iray and usually get results I like with it. But whenever I want to render something in an enclosed space, render times get out of control and I still end up with noisy renders. I know about doubling the size (although I wasn't dropping the samples—doh!), and that helps some. I've tried the architectural render mode, which has always increased my render times without helping quality. But I don't know what else I can do. It's frustrating because I have a bunch of scenes I want to render that I'd like to put in closed room. Is there any good way to deal with this other than always leave off as many walls/floor/ceiling as you can get away with?
With indoor renders, I'm usually using a combination of mesh emision lights + an HDRI for light coming in through any windows.
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The general issue is low and indirect light, two conditions that can cause long render times. Depending on the look you're wanting to achieve, you can try things like hiding or removing the ceiling, so your HDRi shows through. If your interior doesn't have removable ceiling parts, there are other methods that can work, such as selecting the ceiling surface and reducing its Cutout Opacity to 0.
When all else fails, there's the Iray section plane feature, which "cuts off" geometries along the plane. With the roof/ceiling of your interior removed, more and direct light can show there. There have been several threads on this topic, like this one:
http://direct.daz3d.com/forums/discussion/64447/section-planes-cut-down-render-times
Thanks. That's great info. I don't spend a lot of time on the forums, so its easy to miss things like that.
I don't think I want to cut walls with these scenes, but if the problem is mostly not having enough light, I could push the light well past what I want, render to a canvas to get an EXR file, then bring it all down in Photoshop afterwards. It'll be harder to pre-vis, but I guess if I just mutliply the output on all the lights by 10, it should be the same once adjusted for exposure.
Remember that you can rotate the section plane, so it's possible to dissect the room from an angle so that part of the ceiling is still visible. And you can remove walls behind the camera, which will admit direct light into the scene. It's not just the amount of light that's a concern, but indirect light. The architectural filter is one of the features designed as a "light helper" for this, but it's not universal. Iray has another helper for aiding renders with a lot of indirect light, the sky portal. Unfortunately, D|S doesn't currently support it.
What do you mean by " I know about doubling the size"? I'm looking for tips on how to increase render quality in general.
@Tobor. That's bad news! :p I often don't want a lot of indirect light coming from an HDRI or something—just the lamps in the room. Something like removing walls changes the nature of the light as well as the volume. Sometimes that's not bad, but not always. So strange the difference between "biased" and "unbiases" engines—with the former, you want to limit bounces with barriers. With the opposite, it appears that just causes noise.
@Tristanthorne: If you reduce the max samples, but double the final size, you can then half the size after the render and get a good result. The important thing is that you're not rendeirng to the same percentage merged—you might be able to stop at 50% instead of 95%. That can cut render times down significantly.
You mentioned you were using an HDRi image. The image defines the quality of the light. If you use an indoor HDRi for an indoor scene, it looks perfectly natural. You get the benefit of the light being direct, and you get faster renders.
I have a window in my scene that casts one color light (in this case, city lights), and then lighting in the room (lamps, phone near the face) that casts another. The nighttime light isn't such a big deal—I could probably use a room-like HDRI or even render out an EXR in Modo with the lighting I want. But the combo is hard. For the render I'm doing now—a studio with daylight windows, I just put up a partial ceiling to prevent the blue sky from coloring the indoors from above. It's not ideal, but it works okay.
About how long is 'out of control'...and is this for stills or animation?
It can be a challenge, but it's the same if you were lighting a set on a sound stage. There, ceilings are incomplete or not there, and the walls are removable. Yet they somehow get the lighting to look right. Iray is no different from an artistic point of view. The fact that it won't let light pass through opaque, solid objects should not be considered a limitation, but a challenge!
You can often decrease render times just by adding some ambience lighting inside the room. If the room is supposed to be cast in blue light, you can remove a wall (or two, or part of the ceiling), and create for yourself a medium blue HDRi image in Photoshop. Bring that into Iray, set the Environment Intensity accordingly, and you've added blue ambience that will fit the color and mood of light coming through the window. You've also given Iray a few more photons to work with. It's the multiple photons (ray hits) on any single pixel that contributes to the convergence ratio; the more hits to any pixel, the shorter (generally) the render.
(Edit: Oops, meant decrease)
HDRI quality and amount of light is the key as I just did a test http://www.daz3d.com/forums/discussion/comment/956120/#Comment_956120 on that regard but it is a fine line between not enough and too much light. For indoor scenes look to watching some vids on setting up a home photography light set up, I found this one helpful https://www.youtube.com/watch?v=toIbDUi8orU
Hi Pete, have you done any testing using "too much light" with Tonemapping settings to pull it back?
Hey prixat
No not yet and I hadn't thought of that truth be told. Could be an interesting exercise
Have you tried using emitters instead of HDRI? A plane emitter in the right place can work wonders in Iray.
If that post was aimed at me geoff6 then my next test will be two emissive planes, one big and one small (soft boxs) and one or two spots just like this https://www.youtube.com/watch?v=toIbDUi8orU
Generally, while emissive objects are not as efficient as Iray's built-in light types (provided in D|S as the standard light fixtures), there is usually a net benefit using them over a dark or fully indirect-lit scene. Still, if possible, make them so they have the fewest number of quads possible. This helps to improve render times, as there's fewer ray calculations that way.
I'm using different shaped primitive emitters on my current project, The Vigilante https://www.youtube.com/channel/UCusbeCQMIgFQNu-vI2Lbkyw The overall colour balance is done in post production but all lighting is done with the primitive emitters, no headlamps etc. Big lumins required sometimes but I love the resulting look
The thing is to experiment with the various options available, just as a lighting cameraman would on a film set and in that environment, little is more.
He's got a nice setup. (And love that accent!) Your tests should be interesting, looking forward to seeing them!
OK I think I have it cracked.
Cube about 4 mtr across, 2.5 mtr high and 8 mtrs long. Iray Plastic white 0.80 diffuse. Used the Geometry Editor Tool to reverse the normals, not sure if I needed to but I did it anyways. LOL
Used Tako's backdrop http://www.daz3d.com/forums/discussion/comment/952985/#Comment_952985 back the same mat as the cloth, floor the same mat as the cube.
Made two softbox lights using planes about the same size as photographers softboxes. Used Lumen output. One key and one fill. I did make an open ended pyramid cover for each of the planes in Blender to stop light from spilling sideways due to the nature of mesh light rays not being perpendicular to the emitting surface.
Two Spots at the rear for rim light.
Three spots on the ceiling above the subject pointing down.
Camera settings the same as he used in that vid. ISO 100 shutter speed 1/125 and Fstop 2.6 I think he said.
and it works.
If I hid the cube enclosing the scene it became too dark, you need to light bounced around the room to make it work in a realistic way.
When I have finished testing I will post the specs or just make a downloadable preset so you take a look for yourselves.
PS I should really attach an image. this was the second HDRI render. The first one took 3 nights to render so about 50 hours. This second one had a better quality HDRI render in 15 hours or so. It will be interesting to see how long the next one takes.
Wow, 50 hours seems like an awful long time for a render of this type. Have you tried doing away with the meshes, and uses a photo studio-style HDRi instead? There are several freebies available. You're using it just for the light, not the backdrop, as you already have that. You'd be looking for an HDRi with umbrella- or softbox-type lights at the usual angles. (Of course they don't have to be shaped like umbrellas or softboxes. All you need are whitish shapes against a black background, and of course a 32-bit file to provide the dynamic range.)
If you want to continue using geometries, rather than try to shape light output using additional geometry, consider finding an IES profile that spills the light more in the direction you want. Profiles work with pointlights and emissive geometries.
50 hours with a low quality studio HDRI and exactly what you describe. Yes a long time for that type of render. Then one I showed above was done in 15 hours with a different, better quality HDRI. I did render it at 3000 X 1688.
I have played with IES I just need to find the appropriate ones.
I have a list...in my sig. There's a bunch of them.
Yep a long list. lol known about it since you made it mjc. :) Cheers..I don't miss much arround here.
OK no IES yet but this took, well I stopped it at 10 hours, probably could have stopped it sooner for not being in bed. :) No HDRI just two light mesh planes and two spots as described above. I think it turned out pretty good.
mjc do you know if many of those IES can be redistributed as part of a scene file?
Most IES profiles are distributed free from lamp manufacturers.
I guess I'm not understanding the use of the meshes. That's what is slowing things down. A good HDRi should render the fastest of anything.
Some of them can...but not 100% sure on a lot of them. AcuityBrands (Lithonia, AEL and several others) has pretty 'liberal' terms on what you can do with them. To be on the safe side, I wouldn't but would say exactly which one and provide a link, so it can be individually downloaded.
Tobor in this test the mesh and spot light took less time to converge the render than the two previous HDRI renders, one a low res studio HDRI and one high res. The high res took less time than the low res. All I am doing is testing different lights to see what speed improvemnts are with different lighting as per the OP's question.
great suggestion I think that will be the best idea, cheers mjc
The easiest to deal with, as far as a package, is the 'Artist Friendly' package...I put it (and several others) in an IES folder in my Runtime > Textures. That way it's easily findable and in a central location.
I have tried the "make it really bright and tone map it darker". It just occurred to me (thanks to Tobor) as well, not that long ago. I liked the result, but haven't tested it in a variety of conditions. It was significantly faster than trying to tone map for a brighter image.