R15 GI Flickering

[Adam Trachtenberg]

The GI in R14’s physical render settings was nothing more than QMC, so if you want the same result … use QMC. Unfortunately the other option is to bump up the cache settings and do a bunch of test renders.

[Chris Pettit]

[Adam Trachtenberg] “The GI in R14’s physical render settings was nothing more than QMC, so if you want the same result … use QMC. “

Thanks Adam, that’s what someone else said as well, but when I tried rendering with QMC the render times were wildly longer that I remember IL being. In R14 the render times were tolerable, with QMC it seems prohibitive. Is it possible that it works the same but is slower? Or maybe its that there are so many more settings for QMC, my settings are not correctly applied to get back to the simplicity of IL. I’ll work on it.

[Adam Trachtenberg] “Unfortunately the other option is to bump up the cache settings and do a bunch of test renders.”

Is the source of the flickering most likely resident in cache settings? If that’s the area to focus on, I’ll start new renders and see. Thanks so much!

[Adam Trachtenberg]

Okay, I’ve done some testing and I think I’ve figured it out. Basically, the old indirect illumination from physical render was relatively fast because it was using a low sample count — much lower than the “low” setting in the QMC default.

I find I can get a slightly better (less grainy) result a little faster using the following settings:

Primary method: QMC
Secondary method: Radiosity maps

Custom sample count: 24
Radiosity map sample density: 50%

Everything else at default.

Give it a shot and let me know what you find.

[Chris Pettit]

Spectacular Adam!

Not only is it rendering very fast, faster than r14, I’m seeing less noise. Very clean render, and of course no flicker. Can’t thank you enough for your time and expertise.

I also discovered that your previous input regarding cache settings also produced good result when using the Irradiance Cache / Light Mapping method. I increased record density to high (from medium), and smoothing to 100% (from 50%). This produced largely flicker free renders with a moderate increase in render times.

But the QMC method appears even faster, and operates just like IL in 14.

Thanks again for your help, my guess is this will help others who are making the transition from R14 to R15!

[Adam Trachtenberg]

Glad I could help. Benefits me, too, as I wasn’t paying enough attention to QMC.

[Darby Edelen]

Looks like Adam already has you covered on the QMC front 🙂 I’ll just add that the Sample Count in GI is directly related to the Indirect Illumination sampling subdivisions in the previous Physical Renderer options. The number of samples for a given pixel was equal to the square of the subdivisions in R13/14. So If you entered a value of 4 subdivisions in the Indirect Illumination tab this was equivalent to 4 * 4 or 16 samples in QMC.

I’m not sure if you were saying that your animation consists only of camera animation but if so the settings you’d want to change are on the “Cache Files” tab of the GI settings. Disabling the “Full Animation Mode” checkbox will render the caches as a Camera Animation.

The new Light Mapping GI mode is a good alternative/addition to Radiosity Maps. You can still “Build Radiosity Maps” through Light Mapping to speed up QMC or IR calculation but you get the added benefit of many many more secondary light bounces. On the downside light mapping can sometimes introduce subtle splotchy artifacts or softness in shadows so settings there may need to be tweaked as well. The documentation goes over this really well. Also if you’re doing camera animation (and only if so) you’d want to enable “Use Camera Path” in the Light Mapping settings.

Darby Edelen

[Chris Pettit]

Thanks Darby for all the additional information! Very helpful.

I got a little lazy I think with R14. IL was a quick and fairly easy solution, I need to re-do my homework a bit now in R15

Thanks again

[Arvin Bautista]

I just wanted to reply to this and thank Adam for his suggestion. My renders are flicker free and rendering even faster than the default setting.

Arvin Bautista
Greasy Pig Studios
Los Angeles, CA
https://www.greasypigstudios.com

[Jason Clyde]

Apologies for unearthing an old thread, but I’m having similar issues… I bumped up the IC, and when I cache my IC, LM, and AO, I still get extremely long render times with team render. I’m only doing a camera animation, so no moving objects. It’s like the caches aren’t even being used by the team render clients. Anybody have any idea what is going on here?

Thanks!

[Jia jia Wang]

Thank you so much!!!