Flashes of light during Eevee renders?

I’ll preface this with an apology because I’m canadian. Sorry if this has been asked a thousand times I’m not even sure how to google it beyond flickering lights in EEvee renders.

I am having an issue when I render in EEvee where I get these little pots of light, at first I thought it was lighting sources that were way too bright bouncing off reflective surfaces but it’s happening in random low lighting situations as well and I was hoping someone could let me know if there’s something I’m doing that’s causing it or if it’s an actual issue.

You can see it on Frame 18 of my example below.

Imgur - Example
Giphy - Example

If there’s anything else I can attach to help figure out what’s going on I’d be happy to.

can you upload your .blend file?

Pasteall.org/blend/ is a handy platform for sharing .blends.

I was a dummy noob and just kept working on that file and didn’t save it before I posted this so I went through some older projects that were doing the same thing and I was able to reproduce it in this one.

Giphy - Example

Pasteall - Blender Project - Tubes.blend

So, the pointlight that is rotating around the veiny tube thing is causing sharp glossy highlights.

You can eliminate that by reducing the specular value of that light:

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Thank you so much I’m going to play with that. That was very helpful!

I tried turning the specular value down on the lights, that didn’t work so I tried removing it from all the materials, but it’s still happening unfortunately.

Here’s my blender file with all the changes.

Blender File

Sorry, but I don’t get what your seeing on yours at all, I only get a transitional flash when it re-starts from 300 to 0, and you get that same effect in eeVee when the shaders have to update…if rendered to an anim file it never happens.

I got rid of that by turning off screen space reflections, which wasn’t really doing anything. It now plays at 128 samples at 60fps without a glitch.

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Why does the volumetric cube not cover the entire path of the tube? Is the problem still present if you delete volumetric cube?
Instead of that cube, you could try setting up a volumetric world.
Ok, I see they are instances there. Anyway I would like to know if the problem exists without volumetrics in the scene, or with volumetric world instead of those cubes.

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Did you try to render it? I have a few renderings attached at the top that show what happens during render, these flashes do not show up when I’m scrubbing around the timeline pre-render.

I tried to post new examples but I got in trouble for spam when I used giphy links, what service can I use to send a webm or mkv/mp4 of the resulting render so you can see? (Or check my first post about this at the top there’s still a giphy link there)

Yes I’ve had this issue without volumetrics present, I will remove all volumetrics from this blend file and do a render and let you know, thanks!

I think you may be onto something about the volumetrics, I might be mis-remembering flashes from renders I did before I started playing with volumetrics. I’m gonna keep playing with this thank you for the insight, everyone!

You try removing those volumetrics cubes and setting up volumetrics for the World. Then you could try Light Clamping in Volumetrics settings, for example starting with a value of 20. If the problem still persists, a value of 10 or 5.

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Thanks, I just removed the cubes and changed it to a Principled Volume for the World and I’m trying another render, seems good so far, I think the contained volumetric cubes were a mistake :smiley:

I’ll post again if I see flashes on the render but it’s looking great so far, thanks for everything.

I will adjust the clamping if there are any more bright spots.

Thanks for the support everyone, I’m new to blender but I’m loving it.