Very Grainy Image on Iray Render
Prince Wao
Posts: 373
Having for the most part resisted Iray since it first appeared (though I've purchased 3 x Iray only scene products for experimenting), I really liked the recent Wisteria Tunnel product (see link below) so I bought it with the intention of finally doing a whole Iray render. I've used the default settings which come with the product, my own camera angles, and added one of my self-morphed G2 female characters, using the Iray material for her. The full image size is 4000 x 2500 pixels (though I first tried a much smaller size as I always do on setting a new scene). The first and all later renders took a few seconds over 2 hours, but the first ended up very grainy. I had to very slightly alter the angle on the character to get both feet flat, then did a second render which for no known reason was slightly less grainy. I then checked the Forum and found one guy say that using the Mitchell filter lessened graininess, so I chose that and did a third render, but it was only as clear/unclear as the second render with the Gaussian filter. I next altered the character's outfit and did a fourth render, again using the Mitchell filter, but bizarrely it came out even granier than the previous. I've attached a cropped portion of the image which is very grainy. So, what do I need to faff around with to get rid of the graininess? On other discussions I've read that there's more graininess on a larger image, but I need the size I'm rendering as I design for print. I also read that lengthening the time of render can improve the final image, but as I've never had to do that in over 5 years using 3DL I didn't even know render time could be increased. So how is that accomplished with Iray?
So two basic questions:
1: How can I get a non-grainy render?
2: How do I increase render time?
https://www.daz3d.com/wisteria-tunnel
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Comments
How is the scene lit - if you are using the defaults it will be the Ruins HDR. Is there a skydome or other environment prop surrounding the scene?
It sounds as if you render is running out of time - two hours is the default - so you may want to increase the max time in Render Settings.
That's because the default render settings tell Daz to stop rendering at 2 hours, whatever state the render is in. You need to go to the "Progressive Rendering" bit of the REnder Settings, and up the "Max Time (secs)" as high as it will go. While you're there, push up the "Max Samples" too.
You may find that adding more light, or increasing the power of the lighting you have, decreases render time and graininess - experiment with boosting light levels, then adjusting tone mapping to compensate. If you look carefully when you're rendering, on theleft hand side of the render window there's an arrow. Click on it and it opens a panel where you can change some render parameters in mid-render, which can be useful when making adjustments.
If you really want to understand Iray render settings, I HIGHLY recommend this video. It's long ... 2 hours ... but it not only covers render settings, but also some basics about Iray materials. By far the most comprehensive tutorial I've seen on the Iray render settings editor.
Thanks Richard and Chris! I only loaded the scene's defaults, so I didn't use any sky dome. I saved the render as a PNG so had it been successful there would have only been a few void areas in between the foliage and I could have layered the render over any backdrop.
As one doesn't have to set a time limit for 3DL and as my 4k pixels wide UHD renders can take anything from under 15 minutes to over 13 hours it's impossible to know how long any image will take to render before starting - some I think will be quick but aren't, others I expect to take hours but finish sooner - so it seems very bizarre that longer rendering Iray shouldn't just continue to render until it's 100% done, as does 3DL.
Chris wrote; "You need to go to the "Progressive Rendering" bit of the Render Settings, and up the "Max Time (secs)" as high as it will go", but how high will it go? What ludicrous number of seconds should I input? And weird that it should be seconds and not minutes or hours! I just completed a 3 hour render, hoping that would do it, but it didn't, so I have no way to even guess if I should set it for 6 hours or even 12 or more.
JohnnyRay, I've just seen your comment so thanks for that link! I'll definitely watch the video.
A tip, in case you didn't know... aweSurface and scripted pathtracing for 3Delight is an option for those who render on CPU, the commercial kit has an IRayUber to awe converter if you don't want to convert manually. (Haven't tried it so don't know how well it works). Renders roughly 4 times the speed of IRay with about the same level of realism when the CPU is used. And the aweSurface along with some other useful stuff can be downloaded free from the freebies section if you want to try it out.
1. Use a denoiser. There's one in 4.11 beta or you can use an external denoiser.
https://declanrussell.com/portfolio/intel-open-image-denoiser-2/
2. Just don't. Iray will always have graininess in dark areas no matter how long you let it run. A denoiser is the only way to go. That is, unless you want to render forever.
You'll have better results changing the scene lighting, render settings and using the Intel denoiser! :D
I'm beginning to think IRay is seriously flawed
It isn't that bad. Have a look at the images on my Art Studio thread. They aren't great but they aren't terrible either
Yeah first buy a new computer to be able to do ultra realistic renders..BUT not low light renders...need to flood the scene with light, then do some postwork...remove the ceiling? Make it emissive? Remove walls to let light in? Hahaha farout!!! (ok I'm calm now...carry on people)
CPU only here.
Using light sensibly is a start. Not too much or it causes Fireflies, too little and the wrong render settings and it causes grain. Too much contrast between dark and light areas causes longer render times too. A strong light in frame can cause a lot of bother too so move the camera so it is out of shot.
I don't do postwork.
Emissive I use all the time on lights, indoors and out; on the ceiling for ambient light, I don't remove it or any walls. In fact I add a primitive plane as a wall when there is an open end, I also use primitives set to emit light as fill lights.
Perhaps I'm strange
Sorry Fishtales, I was not addressing you with my last post;) You seem to know IRay inside out, and I've seen the numerous posts you've made to help people in trouble, I've actually picked up quite a few "good to know" things about IRay thanks to you:) But I do think that DAZ could do more to help newcomers, no matter the renderengine. I mean how hard could it be to have an answer to the most commonly asked questions like "why are my renders so grainy/dark/other?
KindredArtz light sets have really revolutionized my relationship with Iray lighting: https://www.daz3d.com/kindredarts
I wouldn't suggest you to remove the ceiling, to use headlamps or to use the Iray Interior Camera...they're easy fixes, but the final results are...anonymous at best.
Iray is the only reason I'm rendering, personally I would have never even started if 3Delight were the only available tool!
In general it's not as easy as it seems...I'm still absolutely a noob after 6 active months.
But astonishing low-light renders are achievable, just look at this artist's gallery: https://www.deviantart.com/kmcbriarty/art/Demon-Inside-v1-2-770219204
Actually I like to post-process too...I've always loved Photoshop :D
Regarding your PC, if you aren't using AMD you probably have something good enough! For example, if you've bought your PC for gaming, you're probably using a 1080p monitor and you probably have at least 60fps in modern title, that means a 1050Ti, that can do a lot of stuff!
Here's Steam hardware survey regarding GPUs: https://store.steampowered.com/hwsurvey/videocard/
Most of that people have a GPU that's better than mine xD
I knew that Sven but I thought I would address your comments as you are correct in what you are saying. I see the same things rolled out time after time as a fix and think, why? Some of it might work sometimes but I find that nearly every render needs to be tackled in a different way every time, I haven't found a one fix system yet
Yeah thank god we're all different, with different goals:) I make a living making music and everything related to that, also run my own recording studio. Been a Mac user since 1985 or something, have no interest whatsoever to get a Windows rig, as my current Mac is totally capable of rendering in IRay, although it is 4 times slower than scripted pathtracing with 3DL. I just love playing with 3D and 3DL as a hobby, 3DL mostly because it's a biased renderer, and because it can be dumbed down for blistering fast animation when needed. It's all good, you grab the tools you need to get the job done, right=)
Oh, one of my friends had that same problem with Logic Pro X being Apple property!
Mac machines can't use Nvidia GPUs nowadays, and Iray is an Nvidia product meant for Nvidia GPUs, everything else is often too slow! But in any case, Iray is meant more for quality than for speed.
Have fun! :D
What problem
...
I think IRay is meant for selling NVidia GPUs
You too:)
The maximum value is 259200 seconds - which is 72 hours or three days. That ought to be long enough for anything, and it's the value I use. I believe if you set the max time to zero, it ignores time altogether when deciding when to stop.
That's the thing about progressive rendering in Iray. In 3delight it works through the image pixel by pixel, and when it reaches the last pixel it knows it's finished. Iray makes a number of iterations rendering the whole image, and will go on forevery unless you tell it when to stop. The settings allow you to set three stop conditions, and the render will stop when any one of these is reached:
Max Time - stop after this number of seconds
Max Samples - stop after this number of samples
Rendering Converged Ratio - stop when the converged ratio reached this percentage
The converged ratio is the only one that takes any account of the quality of the image being produced, and it's the only one (in my opinion) that you should allow to stop a render. My (limited) understanding of what convergence is is that its the percentage of pixels that didn't change between this iteration and the previous one - which is why it spends a long time on 0% at the beginning, rushes through the middle percentages, and then stalls in the 80's and 90's as it works on the stubborn last few pixels. Apparently it's impossible for it to actually reach 100%.
So my advice is to set Time and Samples to big numbers or to zero to take them out of the equation, and put everything on convergance. But also to look at what's being rendered. Sometimes you can have a convergance of 80%, but it looks fine to the human eye. In which case, stop it! What else are you going to look at it with?
I used to think that, but if you make a simple scene, like just a sphere and let it go, it'll stop pretty soon, even with convergence set at 100%. If you turn Rendering Quality off, then it'll keep going.
I have mine set at 7,200,000, what is that? 83 days?
Max samples is at 15000 and neither of them has reached that with the Converged Ratio set at 95%.
Thanks to everyone for all of the info above! Like an Iray render itself, it's a never-ending story!
My first full Iray render experiment was a success, simple as it was, but I set the time limit to maximum but in the end I didn't need it go all that way. After 5 hours the render looked complete to me, but just in case it wasn't I let it go for 12 hours, though even then it looked no sharper than previously. I decided to let it run overnight, but after 22.5 hours it looked no different, so I stopped it and when transferred from my LT to my PC which has a bigger screen it looked perfect, other than the default bench in the Wisteria Tunnel set wasn't needed. So I deleted the bench and did another render, again overnight, ans after 14.5 hours of rendering I stopped it. I compared it to the 22.5 hour render at 200% scale and above and if there's any difference I can't see it. In future I'll stop the render whenever it looks sharp, even though the % bar is way less than 100%.