Need Help With Flickering Lights on Voronoi Texture (Cycles)

Hello everyone!
I’m new to Blender. Just made my first donut about 3 months ago and now i’m trying to turn my after effects sci fi movie into a 3D blender style movie. Anyways. I’ve run into an issue where my space station lights made using a voronoi texture (the pink and orange ones) are flickering really fast in my cycles render. The blue and red antenna lights are supposed to flicker slowly, but the orange and pink ones are not supposed to. I found a similar thread here that I followed and tried to bake the texture in (final shader node result in the posted image) but it didn’t work. Any advice on how to fix this would be much appreciated.
Below is a twitter link to the rendered video and an image of my shader nodes of the space station.

Try to reduce the scale parameter on Voronoi texture nodes, you probably also need to link the mapping (vektor) to the orange node

Welcome to the community!

I think you might have a problem with denoising here.
I am going to guess you are probably rendering the image with a relatively low amount of samples and relying on the denoiser to clean the image. Denoising can be a problem in animations, because the moving objects mean that the noise will be different between frames and the denoiser will interpret each frame slightly differently. This can cause small details to flicker and is a well known problem called “temporal coherence”.

One thing that could help is to simply render with way more samples.

If that’s not an option, I have an other technique to suggest:

1-Render and denoise your image at double the current resolution. You can reduce the samples so it takes the same amount of time it did previously.

2-Save the render result still at double resolution.

3-Take the images to a video editing software and reduce them back to their intended resolution. Because they were denoised at a larger scale, the denoiser will have understood the fine details better and the image will be more crisp. I don’t recommend doing the reducing in Blender’s sequencer, because it has rather bad filtering when rescaling images.

I guess I should have told you my render settings lol.
540 samples
with denoising on
256x256 Tiling
with those setting i’m getting about 45 seconds a frame on average so I can definitely increase the samples. I’ll try doubling them to 1080 first and see the difference. thx.

I’ll try scaling them down a bit. I initially thought to link the orange node as well but when I did the orange lights just disappeared, so I just left it like that.

I see that you mention tiling settings. This makes me ask: what version of Blender are you using? If you are in a version pre 3.0, then those settings are fine. If you are in 3.0 or later, you would want to disable tiling if possible (in the newer versions, tiling is only there if you need to render huge images and is generally bad for performance).

Also, it’s not just about the number of samples. The number you have would be well enough for most scenes, but if you are using noise threshold (aka adaptive sampling), you could be having a problem where the sampling stops too soon if the threshold is too high or the min samples are not high enough.

Emissive materials are generally harder to render for Cycles, especially if there are many different sources. This could be a scene that requires lots of samples.


Im on Blender 3.1.0
Render Settings are:
Noise Threshold checked (0.0100)
Max Samples 540
Min Samples 0
Time Limit 0 Sec
Denoise checked
What would suggest?

So the tiling thing. I did tests and each frame I was saving 30 to 40 seconds by using tiling at the same sample rate. So it definitely decreased the render time, and the images looked the same in photoshop.

Those render settings are fine. Depending on your system, cpu/gpu and if you are rendering with just one or both enabled, it’s possible that tiling still does help.

I have just done a quick test and I believe I have found an other possible reason: you are using the glare node in the compositor and the quality level is not set to “high”.

whelp, you might be on to something. it was definitely on “low”. I’ll render over night and let you know the results tomorrow. thanks for the help!

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Oh yeah, that would cause flickering. The low setting uses a lower resolution version of the image as the basis for the glow, so little bright dots will flicker in and out of the effect.

that was it! Thank you so much!

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