Dark, moody IRay renders that aren't grainy? Suggestions?
Ptrope
Posts: 696
The one thing I really don't like about IRay (and Reality, for that matter) is the graininess in renders that haven't had the hell lit out of them. I just can't seem to hit upon the combination of light, film speed, f-stop and exposure that will let me have a sharp, smooth, gainless image with high contrast or a dark, moody feel. Are there any rules of thumb, guides, or even working presets? I don't want to only render washed-out images with no contrast, but I can't seem to get rid of the grain otherwise, unless I use 3Delight or Poser's Firefly.
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I don't know - maybe light your scene too brightly nd that adjust gamma externally to make it darker? Maybe re-render with the gamma set purposely to make the image too dark?
You can try messing with the tone mapping settings in the final render. Turning down the ISO makes the image darker and sometimes can make a "daytime" or relatively well-lit image look like night.
Laurie
My Go-To settings for dark scenes are
In Progressive Rendering settings
With the above settings, the only parameter that will automatically stop the render is "Max Samples". 15000 is the maximum limit, but you can go into the parameters and change the upper limit, or turn Limits off completely so you can set it higher, should you need more time.
In Optimization, (IIRC, I'm doing this from memory...)
I've observed, at least in versions up to the latest DS release, that Iray gives priority to the light areas and cleans up the dark areas last. That is why, (in my opinion,) the lighter areas of your render look finished, while the dark areas look grainy/noisy. With Architectural Sampling on, Iray appears to render the scene evenly, so when the light areas look right, the dark areas should as well.
But... unless you have a killer system with one or more Nvidia cards with lots of memory and lots of CUDA cores, you should expect these renders to take quite a bit of time.
Light it at normal levels with fairly diffuse ambient lighting and a few harsh lights, then darken it to where you want in post
Bingo! Circle gets the square ;-)
The globe from Ghost Lights 2 is what makes this render work. Skies of Irradiance, SickleYield's Fast Flames, and some random emissives are also involved, but the invisible globe of light in front of the birdwoman and the other invisible globe of light in between the reptilian and Ahmad are what keeps things from getting too grainy.
I do alot of dark stuff the second one took less then 10 minutes
Will got it right. Look up the technique "day for night" that film makers have long used, and read about how it's done. Same concept (though for them, it was a matter of having enough light for the film emulsion).
L'Adair and Will both got it right. Will's technique is great for dark scenes, Hollywood does that all the time. And L'Adair has also proved that method in previous posts, which is also helpful in fairly well lit but less than perfect scenes. I've tried it myself. Ghost lights will also help with discretion if it's a truly moody scene.
if max samples are not long enough turn limits off and up a million
Ghost lights work really well for this because they flood the scene with diffuse light, lack specular. This produces a more convincing sense of dim light when darkened than conventional lighting
So what you're all basically saying is, "PBR doesn't produce decent images in your lifetime unless you want noon in Phoenix - use 3Delight for everything else." So much for 'realistic' lighting. I may give the ghost lights a try, but I've never been convinced by 'day for night' photography, and I don't really want to spend my time dodging and burning a render that I could get in camera using a non-PBR.
@Ptrope "PBR doesn't produce decent images in your lifetime unless you want noon in Phoenix"
No one is saying that. Get a good Nvidia card and you'll get results on a bearable tiome frame. I also don't remember being able to nightime scemes in 3DL without very longer renders either.
PBR is Physically Based Rendering. It is a model of reality, not reality itself. Using the tone mapping tools is rendering in camera.
Since you mentioned camera, ever tried to get a photo in a dark room without grainy areas? Takes a very good camera / lens or some post work.
Yes, that's mostly my impression. It is very tough to do without obscuring the problems via postwork or doing a portrait on portrait style background.
However, you can improve that, if you find and use high quality HRDI images and use them as a light source (you don't have to include the HRDI image, and they tend to give me noticable problems of scale and clarity even the high resolution HRDis because the DAZ models are rendered so sharply (turn on environment blur for the HRDI itself and/or up gausian filter for the models to 2.0 from default 1.5 and adjust to taste if you like), in your render Draw Dome - off) they tend to give, unsurprising, the most realistic lit renders, regardless of time of day. There are lots of sources and many of them are good sources too. To point you to 1 good source I point you to Greg Zaal's HRDI freebies which he posts in the Freebie section of the forums periodically.
Try an old theatre trick. We achieved the illusion of dark rooms and night by using a very dark set. Then, we applied blue gels to the lights, but kept them at full intensity. The actors could be seen by the audience, but the scene looked dark.
So, darken your set. Lower the diffuse colors to absurd levels, like 100, 100, 100. Props and clothes if need be. Then light it as normal, but use either blue via RGB (a little goes a long way, such as 225, 225, 255) or temperatures at 8500 - 9900.
If you are looking for an excuse to not use Iray, fine, it's terrible at everything.
But otherwise, treat it like a camera, and use real world tricks mentioned
That's the easiest & best tip I've read yet. Thanks
Seems like it, but not really true. There are lots of tricks you can employ to get the look you want without sacrificing quality or having to wait a couple of weeks for the image to finish rendering. Several tips were presented above. Here's another one: Double the render size of your image, then size the finished image down by 50% in your photoediting program. Reducing the size will remove a lot of the noise without losing the details. You don't have to know just when to stop the render, either. Hit cancel, and then go back to Daz Studio proper. Use the File menu to "Save Last Render," and reduce that image. If you don't think it's rendered enough. Go back to the Render Window and hit Resume. (Just DO NOT close Daz Studio to work on the image...! Or you'll have to start rendering from the beginning.)
I feel your frustration. I rendered in Iray via CPU Only for over a year and a half, and I can relate to how hard it is to wait for those long renders. I have one image I let render for six days. Even then, I only stopped it so I wouldn't miss a contest deadline! Hang in there.
Here's a gloomy picture for ya that's not grainy- I used Iray ghost light to illuminate the subject in addition to an HDR light set for the background scene.
Give you an idea of what it looks like. These lights are at full blast.
http://nathanomir.deviantart.com/art/Night-of-the-Wraiths-678917968
It was slow, but it was also my first real render in Iray since getting a machine that could handle it.
This is very like what they do for film. Even for night time and dark scenes, there is a large array of high wattage lights on almost all the time.
One thing I find odd about Iray...I realize that it is using "real world" reflections etc., to translate the scene to an image. That makes some sense that dark scenes would be grainy and noisy. However, no camera actually exists in a physical sense. So, there is no need to mimic the low light performance of a camera. Iray should be able to make the dark scenes almost black without introducing grain and noise. I mean, it "knows" exactly what is in the scene and can see the subject with no lights at all. So, even with the approximation of how a physical camera's sensor would see the scene, Iray should still be able to render it without noise. Just food for thought.
That blurriness is just how my eyes react to light in the dark too. That is good. I was also paying attention to the way my eyes see straight edges compared to edges that are arcs i n real life objects not rendered images. The arc edges were somewhat blurry to my eyes while the straight edge clear and sharp. Must be PI at work in my eyesight and brain.
I think the problem is not that that don't know what's exactly in the scene, the problem is they don't know all the physical radiation and material properties of what's in the scene and what they do model must be calculated. Otherwise the openGL viewport texture draw scene is what the scene would look like, which I admit I often like better then my attempts at iRay.
I wonder if Iray couldn't implement some second stage noise reduction...the main pass to calculate all the camera and light parameters, and the secondary pass to remove aberrations like green dot noise...etc.
A lot of people end up with underlit scenes and try to increase exposure to compensate, which doesn't work very well.
I'm wondering... maybe people should overlight their scenes and then _reduce_ exposure. Anyone test if that suits Iray better?
I will try it will Alsace in the next couple of days and post it here instead of using the Alsace nighttime iRay light HowieFarkes provided (although I want to try that out too. I've already seen a couple monthes back someone time a really good nighttime Alsace render with 3DU toon animals in it but I don't know how they rendered & postworked to get it looking nighttime.
@timmins.william
Iray wants light to converge faster. You are better to use more light and tone map for darker scenes. There will also be less grain that way. I'm also wondering how many people realize that Iray has noise filtering built in? It's not as good as most editing programs, and is OFF bt default, but it may work well enough.
If your scene is outdoors, you can also simulate moonlight and night by changing the white point to 255, 212, 212 (you want the color opposite of blue-white). Add a photometric spotlight w/ color temp 10000K for the moon. Use a distant light for shadow casting and Environment > Ground Shadows > 0.5 for less dense shadows. Set your HDRI levels and spotlight levels to taste.
If one is having troubles with dark scenes, I'm personally in favor of lighting as if were day and then changing the exposure in render settings. More than anything it helps make it easier to see what one is doing while adjusting the lights.
And in case one is wondering how realistic this is here's a nice picture I once took of a sunny day look at those crisp shadows... wait, are those stars? :)
Point being I figure that if a nightime picture with long exposures can look rather like day in the real world, then I can probably use exposure to make a 3d scene with daytime lighting look rather like night too.
I did this one, started as a quickie but took longer than I had hoped. The only light is from the Milky Way HDRI in the dome.
Lighting from Milky Way HDRI
2017-06-28 06:52:57.144 Total Rendering Time: 22 hours 19 minutes 58.38 seconds
This is the Daylight version.
Through the Woods and Deaddy Bear.
2017-06-27 03:13:48.834 Total Rendering Time: 4 hours 52 minutes 16.70 seconds
Wow, both look good & illustrate the point.
I decided to test out the theory of using more light, then using tone-mapping to make the image render darker. It worked rather nicely, actually. This image is 2K x 2.6K and took several hours to reach 5K samples. I did adjust the levels in Photoshop, but it made only a slight difference. (Some post work corrections, but nothing to do with making it darker or lighter.)
Respite
You can see the image full size via the gallery page, here.