Grainy Iray
LeggyBlond
Posts: 124
Maybe this topic has been covered elsewhere but I can't find it.
I'm tring Iray in a low light indoor sceen and no matter what lighting I use the net result is very grainy much like the render is incomplete.
Any Clues?
Using DAZ Studio Pro BETA version 4.8.0.51
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Comments
How long did you let it render?
(or more precisely, what are your render settings?)
It might help to turn ISO to a higher number, like 400 or even higher.
Unless it looks too dark I leave the render to finish but some times after a time when the render is by no means done it seems to suddenly finish rather quickly.
Well, there's probably just not enough light in the secene. It's kind of like when you are in a very dimly lit room; your vision will also get a bit "grainy" ;-)
You have some options
- increase the amount of light to make the scene brighter.
- or In the render settings, look for a slider labelled "ISO" and increase the number there. Default is 100, which is perfectly fine for daylight pics. 400 or above is a good start for dim pics.
I'd start out with one of these two.
ISO has little to no effect on grain in Iray, just on light level. It's not really a camera, so all of the tone mapping affects aspects of the light level, none of it really affects blur or grain much (you can't get a motion blur using shutter speed in Iray either). ISO 400+ will give you a very bleachy low-contrast render.
If you're getting grainy renders you need to up your number of samples in the Progressive settings. You may also need to increase max time so that it can render long enough to achieve that many samples, and convergence to 99% for the same reason.
It probably is incomplete. The Iray renderer isn't like the 3Delight renderer, it keeps running until either:
* a set time,
* a set number of render passes, or
* a set convergence value (a measure of how "finished" the render is)
whichever comes first. If the light level is too low, you'll run out of time or render passes before the image quality is as good as you want. Go into the render settings and try higher values.
Note that this might mean the render takes a lot longer than you expect before it looks good. This is just the way Iray works; if you want a faster render, use more light in your scene. It's a juggling act; you're going to have to balance one thing against another to get a "good enough" result.
Thank you SickleYield and SpottedKitty
Now that I have a basic understanding of some the parameters it will be some trial and error on those settings that is to say what the correlation is between 'Max Samples' and 'Max Time'. I assume that by simply increasing the 'Rendering Quality' will still require those other parameters to be modified!
It does seem a contradiction that light levels can be increased via the Render camera settings and at the same time individual lights have both 'Intensity' and 'Lumens' settings but 'Intensity seems more relevant to '3Delight' I imagine and the 'Lumens are for controlling Individual lights.
Cameras I do understand very well and it's good to know that the ISO does not affect Quality - non of my cameras are set any higher than 100 ISO..Grainy pictures are for SFX
Yes, the render will still hit one or the other limit value first, no matter how long a time limit you set.
Yes, the render will still hit one or the other limit value first, no matter how long a time limit you set.
It seems I have a whole lot of learning and experimenting to do again. I usually build my own machines but recently I got myself a new pre-built custom machine but that was before I knew anything about Iray. Judging buy some of the configs (Sickleyield as an example) I just may have to add another GPU and upgrade the PSU...Doh!
Barbara
Paraphrasing an official DAZ reply on another thread I read half an hour ago; one of the things about using Iray is you can get better performance just by swapping out a better NVidia graphics card — working in 3Delight, you'd need to get more and faster RAM and probably a more powerful CPU to get the same range of render speed improvement. And speed improvement is all you'll get, the actual Iray render quality will be the same whether it's run on GPU-only or CPU-only.
Paraphrasing an official DAZ reply on another thread I read half an hour ago; one of the things about using Iray is you can get better performance just by swapping out a better NVidia graphics card — working in 3Delight, you'd need to get more and faster RAM and probably a more powerful CPU to get the same range of render speed improvement. And speed improvement is all you'll get, the actual Iray render quality will be the same whether it's run on GPU-only or CPU-only.
Reading some posts, it seems that some people can spend fortunes on hardware without batting an eyelid. I could do a major upgrade if i wanted but for now I'll wait and revert to my older habits for long renders...fire it up, press go, watch the box, go shopping, go to bed etc. :roll:
Pretty much the same here; I'm in no hurry to get new hardware before next year, my current setup is a bit slow by modern standards but still good.
Hi LeggyBlond,
Did you find a solution?
I have only just started to look at iray, but the rules appear to be the same as other render engines I have used.
I can post example of what to watch for and some ways to help with render results if it would be helpful?
But before that (if help wanted), please update DS to at least 4.8.0.55, as that as a bug_fix for firefly filter problem.
Did you find a solution?
I have only just started to look at Iray, but the rules appear to be the same as other render engines I have used.
I can post example of what to watch for and some ways to help with render results if it would be helpful?
But before that (if help wanted), please update DS to at least 4.8.0.55, as that as a bug_fix for firefly filter problem.
Eureka
Thanks to some very good information from SickleYield and SpottedKitty I've worked out some of the essential basics. I've been rendering a Glamour scene which thus far I've done several times with various tweeks mainly on surfaces and the net result is quite remarkable. There is much for me to learn but I'm pleased with what I see thus far.
Using just the Basic Iray lighting (Dome and Scene) set at 0.8 'Environment Intensity' (Dome Orientation Y at 255), 'Max Time (secs)' at full (because the render has plenty of time to be completed), The 'Max Samples' set at max (15000), 'Rendering Quality' at 1.0 (going to notch that up next time), 'Rendering Converged Ratio' at 99% (apparently that's the best setting). The image is 2000 x 2000 Pixels and depending what hair etc. I use the renders vary in time between around 2 to 3 hours which considering the qaulity and size of the render is not a big issue.
NB. - All the Iray Camera settings were left at default!
CPU, GPU and Optix all on.
There is a lot of people here that have multiple GPU's and such which clearly must help but I've just bought a new custom system (I usually build my own) but I bought it prior to knowing about Iray. The Mainboard does have another 16x PCIe slot so I can add another GPU but I would also need to upgrade the PSU.
It may assist some to know my current system configuration:-
Mainboard:- MSI 970A-G43
CPU:- AMD FX-8370, 8x 4.00GHz Turbo: 4.20GHz (Actually it's 4.3)
GPU:- 1 x MSI GTX 960 GAMING 2G NVIDIA GeForce GTX
Drives:- 1x Kingston SSDNow 120GB, 2 x 2Tb Partitioned HDD's (The 2Tb Drives each have 4 x partions)