OTOY Forums

Anyone have any tips on removing flicker from animation renders?

I've got a scene with 4 area lights, a metal table and a midi controller (which is the subject).

The controller has some shiny plastic knobs on it, they're made to look like reflective metal so I've used a silver material which looks correct.

However I've just rendered a slow dolly shot (moving sideways) and one of the reflective knobs is pulsing/flickering (getting brighter and darker), it's doing this in regularly timed pulse.

The other knob which is at a different angle and location is fine.

My render settings are..

Pathtracing Kernel

Samples: 1554
Diffuse: 4
Specular: 14
Ray Epsilon: 0.0001
Filter size: 1.2
Alpha shadows ticked
Caustic Blur: 1
G.I. Clamp: 1.08
Alpha Channel not ticked
Keep environment ticked
Path Term Power: 1
C Ratio: 0
Static Noise: not ticked
Parallel Samples: 16
Max Tile Samples: 16
Minimize Net Traffic: not ticked (not using network render)
Adaptive Sampling: not ticked
Noise Threshold: 0.03
Min. Samples: 256
Expected Exposure: 1
Group Pixels: 2x2

Any tips appreciated.

From previous experience if I rendered this with the PMC Kernel I think it would be fine, but that would quadruple my render times and I have a fairly tight deadline.

Hi Teddi,
do you have bump or normal maps in the knob material?
If yes, try to reduce the power, you should have less flickering noise.
I would also enable Adaptive sampling with the following settings:
Sampling: start with 4000
Max tile : 32
---
Adaptive sampling: on
Noise Threshold: 0.05
Min. Samples: 512
Expected Exposure: the exact exposure that you have in Camera Imager node
Group Pixels: none, or 2x2

ciao beppe

Thanks for this Beppe.

The silver material does have a bump map so I've unchecked that for now.

I also used the settings you suggested but the flicker is still there.

I just tried removing some things from the scene: the table and the four lights (which are area lights placed in front of Kino Flo light models, originally I used a blackbody emission texture on the Kino bulbs but that seemed to slow rendering times down and the lights are so bright you can't see the bulb detail anyway so I replaced them with simple area lights).

With the basic off-white studio and three large invisible area lights the flicker has gone.

So I'm guessing it's to do with what the knobs/silver material is reflecting.

Not sure what to try next.

Cheers.

Hi Teddi,
you can try with the area lights invisible, and by addingbthe blackbody emission to the filament, but with Cast illumination disabled. In this way you can set the power to a lower value with nice reflactions and zero noise.
ciao beppe

Thanks Beppe,

The tip with the lights was useful thanks.

After investigating further I think the flicker problem was actually more to do with resolution or aliasing.

I tried rendering the same scene with the PMC kernel and the same issue was apparent, I changed the metal material for something less reflective and the issue was still there too but less pronounced.

On shots which are further away or closer the issue disappears.

I think on this one particular shot the renderer couldn't resolve the detail cleanly, similar to aliasing or moire in a camera system.

The knob is knurled so the reflections contain a lot of detailed information which changes per frame as the camera moves.

If I'm right some sort of anti-aliasing would help.

Is that possible with Octane or is this a known issue?

Cheers

Hi Teddi,
you can slightly increase the Filter value in the kernel settings, and set the Adaptive sampling Group pixels to 4x4 in PT.
ciao beppe

Will try that thanks.