Grainy lighting, is there a way to remedy this?
karia007
Posts: 51
Hey guys, I was wondering how I could fix grainy lighting? I used most of the lighting settings reccomended on this forum such as - Lower shutter speeds, using the emissive objects instead of just plain of spot lights or distant ones.
My problem is that is comes off as VERY grainy, I'm waiting through a render now to see if it is fixed.
I am confused as to why it is so hard (at least for me) to achieve lighting like this - https://www.daz3d.com/romantic-hotel-room
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These alone make the problem WORSE, not better. The problem comes from insufficient ray hits from direct lighting. The more your scene uses indirect lighting (e.g. light coming through a window or door) the longer it will take to render. Kept at its defaults, Iray will stop rendering at two hours, even if it's not finished. You, too, can render a scene like in your example, if you remove the time limit and wait long enough for the render to fully complete. On a system without a lot of CUDA cores, that may be a long time -- hours, or maybe even days.
1. Changing any of the Tone Mapping settings does absolutely nothing to solve this problem. It's really just a way to adjust the image the same way you'd do in a graphics program like Photoshop.
2. Emissive lights tend to be more computationally "expensive" unless you are very careful how they are constructed. IMO, there are only a few premade emissive light sets sold by Daz that are worth their price. Stick with the later products where the vendors learned what they were doing. People seem to like the Ghost Lights set, though I haven't used it myself.
Specifically, an emissive surface with lots of facets, and/or with other shader values in competition with the needs of light emission, can drastically slow down your render.
3. If you can, use the default image map in the Environment Dome. This works for outdoor scenes or indoor scenes where the roof/ceiling is gone. (Otherwise, the light from the Iray Environment Dome can't get through). This light comes directly from Iray's internals and is very efficient. Rotate the dome so the main light falls on your subject (about 0 to 80 degrees works pretty well).
4. Disregard the distant light unless you want the harsh shadows. This light is useful for quasi-simulation of the sun, but is best as a focused light "projector" for beaming a patterm down at your characters. This is an advanced topic you can tackle later.
5. Add some spotlights for direct lighting. These, and the Environment Dome, are the best way to reduce render time, and get rid of the grainy appearance.
Thanks, I'm trying my best. It's odd because when I use the "Dome" for lighting (Say I remove the ceiling or use a window in the room) it lights up perfectly... Yet the emissive lights only give off a very faint glow, no matter how high I turn them up...
It is very difficult to rely on emissives only for scene lighting, unless you are very very good at it.
Follow point 5 above (whoever said that using emissives instead of point/spot lights was wrong; its not going to make matters better, its going to unnecessarily complicate matters).
When using emissive lights I prefer the product Real Lights for DAZ Studio Iray particularly when operating in scene only mode. I have read a lot of good things about the Ghost Light Kit as well but since I just purchased it I haven't had a chance to give it a try. This scene is lit entirely by the Real Lights emissives and it renders fairly quick although I am stuck with CPU only in Iray so hard to say for sure.
Any grainyness is a result of me stopping it early since it is still a work in progress converting 3dl surfaces to Iray with Mec4D shaders. All of the light fixtures have flourescent tube geometry with its own surface so I used an 85 watt flourescent preset on them.
How are you doing this? With the 3Delight renderer, the lights are controlled with the Intensity dial. In Iray, you shouldn't use Intensity, you should use the Lumens value (for point/spot lights) or Luminance value (for emissive lights). It gets complicated, because you also have to consider the colour temperature of the light, whether there's a colour tint on the light, and a few more etc's.
FWIW, it's this complicated because Iray lighting does a pretty good job of emulating real-world lighting, which is about as far from straightforward as it can get.
That depends.. Here is an old Stonemason set with Iray Uber shaders applied, and the lighting surfaces in the actual scene set as emmisive.
In my experience it is almost impossible to avoid noise in iray. Iray does a very good job in producing a good draft of the scene in a relatively short time, but then it takes forever to converge to a decent quality.
I believe the main problem with iray is the lack of the importance sampling feature. Also it seems to use probabilistic path termination that is fast but tends to generate too much noise. This is most visible in shadows generated from transparent objects shuch as alpha-mapped hair. So the only way I found to deal with iray, if you don't want to wait forever for your renderings, is to just grab a fair good result and then apply a denoiser filter in post.
p.s. I also use Blender's cycles that features importance sampling and deterministic path termination and I can get an average scene converging much faster than iray. Just to show what I mean see the two pics below. Both take about 3 minutes to render (I have a low-end pc), the first is DS and the second Blender.
p.p.s. Also in the iray render you can see the artifacts generated by the high compression ratio for textures. Look at the left bottom side. I left it there on purpose. To get better results you can just set it to 2K textures and above rather then the default 1K textures.
Just for the sake of completeness to anyone who may read this discussion.The current version of Blender 2.79 with Cycles features integrated denoising. So I redid the test above and the results are impressive. While the current DS 4.9.4.122 with Iray stills about 3 minutes as before. The new Cycles just takes about 1 minute and there's no noise at all in the final image.
EDIT: I added a third image made with the new filmic color management in Blender 2.79, which helps emulating the human eyes with a better transformation from linear to srgb. Not really on the topic of graininess but just for completeness. The result is subtle but noticeable.
a good tip for reducing noise in Iray is to render bigger than you want your final image to be and then scale it down,once you scale down all that noise will merge and you'll have a much cleaner image,so if your final image is to be 1000 pixels wide then render at 2000 or even 4000 wide.my promos are presented at 1900 wide but they all get rendered at 4k
in the attached example the original render is 1850 wide,you can see the scaled down version in the inset
here's an uncompressed version of that image https://www.dropbox.com/s/c9uvkz20perm8tf/Iray_ScaleDown_Example_clean.png?dl=0
The issue with that tip is that iray needs to allocate a framebuffer and working space for the whole render canvas in vram. So the bigger is the final image the more vram it takes. So this may not be a viable way depending on your card and on the scene to render. A similar method is to simply apply a denoiser in GIMP or Photoshop. This gets similar results without overloading your card.
EDIT: while Cycles is tiled, so it only allocates a framebuffer for a few tiles and the allocated vram is independent from the final resolution. That is, this leaves more vram for textures and geometry.