Need help with settings of Iray

Masterstroke

How to get crystal clear IRAy render results? The default settings won't do it. So I tried to increase the render times and cranked up the pixel samples, but the results are still grainy No matter, what I do, I allways have some grainyness in my rendered pictures. Can anybody tell me how to do it, please?

nicstt

More light perhaps, or better positioned light. Too little light, or dark scenes can cause issues.

And maybe more time, lots more time; up the quality setting; have the convergence up to 99%.

You may need to increased samples, or time for it to take account of other changes.

JackFoster

Assuming you have Render Quality Enable on, which it is by default, what Convergence percentage is the troublesome render getting to before it stops?

If it's less than 95%, it'll pretty much always be grainy. There are four ways for the render to end by default:

1) If the Max Time is reached. This can be disabled by setting Max Time to zero.

2) If the Convergence Threshold is reached. This can be disabled by turning off Render Quality Enable.

3) If the render is canceled, obviously.

4) If the Max Samples are reached. This one cannot be disabled. If nothing else ends the render first, this one will.

Disabling Max Time is harmless enough. Typically, if your Convergence Threshold is *at least* 95%, the image will look decent, but I like to set mine to 98%. Disabling it would be an option to use if you just want to cancel the rendering yourself whenever you feel like it's rendered long enough and looks good. In order to do that, you'd have to turn off the limits for Max Samples and set it to something ridiculously high. 15,000 samples, which is the default maximum, isn't always enough to ensure that an image isn't grainy. I've never seen an image need as much as 50,000 samples, but it is conceivable. If you want to stop the render yourself, you could set it to a million or so.

Personally, I believe using Convergence to let the render finish is an accurate enough method most times. With a high enough Max Samples, and with Max Time disabled, your render will reach whatever Convergence Threshold you set it to, given enough time.

Masterstroke

Convergence Threshold at 99%, max samples at 10000 and 8 houres render time. It is still looking grainey. Maybe I just have to upgrade my hardware.

JackFoster

Better hardware doesn't result in a better render, just a faster one. I'd be willing to bet you're reaching either 8 hours or 10000 samples before you're reaching 99% convergence. Try setting Max Time to zero and Max Samples to 50000. You'll have to turn off the limits for Max Samples to do so, which you can do by clicking on the gear symbol in the upper righthand side of the slider, clicking on Parameter Settings, then unchecking Use Limits.

Edit:

Also, I meant to say this before, but I just remembered.

Another option is leaving all your render settings the same and doubling the resolution you're rendering at. For instance, if you were shooting for a 1024x768 image, render it at 2048x1536. Once it's done, use an image editor to reduce the size down by half, to what you originally wanted. This results in less graininess in any image, and it doesn't increase render time as much as you'd think. However, it does use more RAM, which could be an issue if you were already using a lot.

Szark

10000 samples should be pretty clear by then. Most interiors I have done clear up around 8000.

Masterstroke

Thank you, I will try that :-)

AndyS

Hi Szark,

 

of cause several thousands of iterations result in a high quality render. The question is, how long needs the render engine. This depends on the hardware, but most of all on the scene itself.

I had an interior scene with only some sunlight entering through the windows. After a full night (over 12 hours) it reached around 20%, but only that little grainy so I could accept it.
That's the central point: It mostly depends on the type of light sources. The more indirect light flow, the (way) longer it takes.
And indirect light flow includes emissive areas as lights and even spotlights using an area capacity. That's what you often use to have softer shadows / lights.

Jimbow

Render at least double or even triple the final size you want, and reduce the final image afterwards. You'll often find the convergence issues are invisible when you reduce the image size and can cut render times significantly. You might also want to make sure your render is set to 'speed' and not 'memory'.

Counterintuitve, but explained here: Quicktip: rendering even faster in iray