Significant grain in image when background included (iray)
brian71_us_5e91777928
Posts: 121
I've noticed a significant amount of grain in the image when attempting to render an indoor scene. This is particularly true where there are shadows in the image.
The attached image is from the same scene with the same lighting. The only difference is that for the image on the left the set / scenery was hidden and the image on the right the set was visible. And this is with the render quality increased from 1 to 5, Max time increased to 173,000 and max samples at 10,000 for the second image.
Without the set it renders in about 90 minutes and looks pretty good. The second ran over 12 hours and was still at 0%.
What am I doing wrong?
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Comments
What is the lighting setup? One likely possibility is that when the scene objects are visible, it changes the way light bounces around in your scene. This can mean the render takes a lot longer to clean itself up.
Check the surface settings of the background object. If it's not required, eliminate any gloss/mettallic/top coats which would introduce reflection or any other unimportant aspects needed (translucence, etc.). Test your render with a background that is a plain object with no textures and default surface settings. Use spot lights instead of emitters. Also be sure caustics are shut off (under Render Settings > Optimization).
I don't mind the render taking longer to clean itself up but it was over 12 hours and still said 0% complete. I can't believe it would take that long or longer would it? I ask because I don't know how all of this works.
It is the Winterblack Sanctuary environment that I purchased recently. There are no emitters in the scene just 2 spot lights and a distant light. Caustics are indeed off. There is a transparent window behind the characters. The goal is to have the moon visible through the window but right now I just have a blank plane. A plane background seems to render a clean image in less than 2 hours.
Just for giggles I tried a completely different scene - the i13 library environment - and get much the same results. Over 12 hours running with no end in sight and the resulting picture is severely grainy.
What makes this so frustrating is that I don't know if this is something I'm doing wrong or if it's a Daz Studio issue.
@brian71_us_5e91777928 The render is taking much longer because the light rays have to bounce around a lot more in an enclosed space. In an open space the rays only bounce against the objects in the scene and then wander off into oblivion, so the render engine can terminate the calculation on a given ray fairly early.
In an enclosed space the rays bounce back and forth between the walls and the objects in the scene, so the engine has to do a lot more work.
If you want it to render faster, remove (hide) all of the walls that will not be visible in the scene.
You can also set the "Max Path Length" to 5 or 6 (this setting can be found under Render Settings->Optimization). Note that you will not see certain reflections in eyes (and other reflective surfaces) when you change "Max Path Length". The lower the value the faster it will terminate the render, but the quality of the render will suffer.
I don't mind it taking longer I just want to understand what is causing the picture to look so grainy
I removed everything that I could and it actually completed this time. However, it still looks grainy in the same spots.
Indeed they can take longer.
Lighting: the amount, and where it's placed makes a big difference; so too, does the amount of reflective surfaces.
This is one of the reasons I use Blender for (all?) my renders; I'm not saying it's easier than Iray, but it suits my workflow and my propensities for tweaking and messing about. Plus it gives me quicker results on CPU than my 980ti - which is a bonus as much as a reason.
And whilst I think about, judge a render off how it looks not by itterations. Looks finished is correct; not not a pre-determined number of itterations is wrong.
Now to me, the first render looks too smooth; I'd be adding grain in post-processing - to simulate the photo-effect.
I'd composite those two images together (Gimp/Photoshop); blend the skin of the two together to get the look you're after; remember: you have a result in mind: you will use various methods and tools to achieve said result.
Thanks everyone for the great advice! You've given me so much to consider.
Try some denoising on the finished render:
https://www.daz3d.com/forums/discussion/316206/denoise-renders-and-save-a-lot-of-time-nvidia-not-reqd/
https://www.daz3d.com/forums/discussion/334881/use-this-a-i-based-open-source-de-noiser-from-the-comfort-of-daz-studio
Except denoising skin sucks in Iray; it removes all character unless it is left pretty much as long as it would take anyway..
The only one ive found that does anything like a decent job is Intel's; the iray one I consider rubbish; no idea what the one available for the RTX cards is like
I'm told in another discussion that max path to 0 is actually the same as 21 so you have to set it yourself to 255 that's the iray max. This could be the issue since energy contribution in dark areas may require more bounces to converge.
Not tested it myself.
https://www.daz3d.com/forums/discussion/comment/5724631/#Comment_5724631
I changed the lighting around a bit and softened the lights so not to get such bright spots. This reolved my issue on this particular image.