Unstoppable Flicker

[caustics77]

Hey All,

Wondering if you can help me. I'm having a horrible time with flickering in my renders. The subject is all "chrome" feeling. I think it's the GI that it causing it. However, I am already using Irradiance map and Light Cache (which is supposed to help with flicker).

I've unchecked "Animated Noise Pattern" in DMC Sampler. My lights subdivs are 32 and there are only 2 lights. I have a similar render that isn't all chrome that is not doing this, so I'm sure it's my "chrome" and or bounces, as it is the shadow result changing per frame.

Small 3 second clip can be seen below.

http://www.patricksurace.com/transfe...derFlicker.mp4

Thanks for your help.

-P

[beenyweenies]

You don't want to uncheck animated noise, that feature helps to keep grain from feeling like dirt stuck to the lens or something. It's definitely not your problem here.

Generally speaking, Irradiance Cache with Light Cache is the worst-case scenario for getting flicker. If you want to "set it and forget it," switch this to Brute Force as the primary and Light Cache as the secondary. Your render times will be higher (depending on the scene, your render times may not be much different), but the problem will go away. If there is some reason that you NEED to stick with Irradiance Cache, you will need to do an animation prepass to save the cache sequence, and use this pre-cache sequence when doing your render. Consult the user manual for more info.

Also, generally speaking, I would stick to letting Vray manage your subdivs unless there's a really good reason you need to do that by hand. Modern Vray is very good at handling those things on your behalf. Uncheck "Use Local Subdivs" in the render settings and Vray will take over. I almost guarantee you won't regret doing this.

[caustics77]

Oh, ok. I was reading the user manual earlier and I thought having "animated noise" on was changing the noise pattern per frame. My thinking is i want to "stop everything".

I don't need Irradiance on, it's just always produced great results for me. I will do a Brute force Light Cache pass and see what happens. Thank you beenyweenies!

[beenyweenies]

To be clear, the defect seen in your render isn't the "noise" that DMC sampler is referring to. You're suffering from classic Irradiance Cache splotching, which can only be fixed by adjusting the IR settings and/or caching it out to a frame sequence.

The "noise" referred to in the DMC sampler is essentially film grain, the very tiny, fine dots seen all over the frame as a result of sampling.

[caustics77]

Gotcha. Presently rendering a new sequence with BF/BF, and it seems to not flicker. I've rechecked "animated noise". I'll try BF/LC after this one. Thanks for the help! For the record, I've rendered a similar scene with a non reflective surface on the ground plane and it's not flickering. That's what led me to think "maybe it's the chrome and bounces?".

[beenyweenies]

BF/BF will increase render times substantially vs BF/LC, with minimal benefit. Using Brute Force as the primary gets rid of the splotchiness of Irradiance Caching. Light Cache as a secondary is usually fine and doesn't introduce any new splotchiness, it's the Irradiance Caching that has trouble.

I could be wrong but I believe the default, recommended render settings from Chaos these days is BF/LC.

[caustics77]

Ok, canceled the BF/BF have a BF/LC on the farm now. I'll post the results of that once they finish. Thanks a bunch. I changed single frame to "fly-through" as well. Read that this will also reduce flicker via caching.

[beenyweenies]

I've rendered hundreds of smooth, flicker-free shots with BF/LC and have only ever used Single Frame mode. You might want to try it both ways and compare render times and results.

[caustics77]

Here it is. All better...now for the 1080 render!

http://www.patricksurace.com/transfe...rNoFlicker.mp4

Thanks again for all the tips! I never had to use "fly-through" before. Rarely do I render all chrome in a "studio" setting...different beast.

[beenyweenies]

How were your render times compared to your first splotchy render using IR/LC?

[caustics77]

You know what?! The 1080 frames (which is what these are in the end) are rendering faster!

[stezza]

Did you really need to have GI turned on? I never use GI if Im rendering a single object, once a light ray hits the object its gone and has no effect as it bounces out into space. Since Vray next I no longer need to bake out light maps BF/BF all the way with threshold down to 0.008.

[SonyBoy]

You could experiment with using the Denoiser render element and the standalone denoiser tool. I've had some good results cleaning up noisy GI this way. The last time I used it I ran a "strong" denoise on the GI element, and milder one on all the other back to beauty passes, and it worked out well. If you go that route, you DO want to turn off Animated Noise, according to the docs, as I guess the changing noise pattern it creates makes it more difficult for the denoiser to identify artifacts.

[caustics77]

SonyBoy, surprisingly the frames aren't very noisy, but I can throw a NeatVideo on them in AE and it's flawless, I tested one frame last night. About the "Animated Noise, that's what I assumed when rendering. Basically, "don't let noise change positions". Sometimes there's a noise flicker too! Render is almost done at 1080 though, so "safe" for this run. Also good to note. I'm using "Fly-Through" as the mode for the Light Cache. I notice the first few frames after the camera changes it's estimating the LC differently and there's a pop. It's resolved by manually rendering, but next time I'd leave "single frame" on as beenyweenies said he never changes, I never have before this either..