Blender 4.5 Blocky Render Artifacts

Support Lighting and Rendering
1

I’m getting these blocky white artifacts on some frames of my render. This is in Blender 4.5, using cycles. There are volumetrics for the dust, and point clouds for the sand, but otherwise it is a pretty simple setup.

It is not reproducible, so if I render the same frame after seeing the white artifact, it is usually gone. But over the course of a ~400 frame animation, I will get a couple dozen of them scattered throughout.

I haven’t really seen anybody else with this issue based on initial searches, so I wanted to see if anybody here had ideas.

Screenshot 2025-11-09 112224

2

Is that white point the size of the rendering tile or is it part of the whole rendering.

And I don’t know if this rendering is CPU or GPU, but have you tried temperature check during rendering. :thinking:

3

Welcome!

Is this effect visible during the rendering, or does it appear at the very end only? It looks a bit like a single very bright pixel with bloom.

Does it happen on both the CPU and GPU? Just to make sure that it’s not the device that’s the problem.

In any case, it sounds like an actual bug, especially if the same frame with the same settings doesn’t always do it.

4

Definitely not tiling, as tile size was set to 8192, CPU and GPU temperatures were nominal during the render I did. My case is currently open for recent fan swap so airflow wasn’t an issue.

5

I wasn’t monitoring during the rendering so I’m not 100% sure if it’s a compositing or render issue. But my node setup is pretty simple, just some chromatic aberration and a film grain effect. I did start using the 5.0 beta and it seemed to fix the issue on a re-render of the animation, so I also suspect there may have been a bug. There are a lot of volumetrics in the scene, and one of the big improvements in 5.0 is volume rendering, so maybe that had something to do with it.

6
  1. If the tiling size is 8192, it may be too big.
    I’m not sure this is the cause of the problem, but my personal opinion is that a large tiling size can put a strain on the hardware. :thinking:

It may not be a problem with still image rendering, but I think it will be a problem if it is an animation rendering.

For air-cooled systems, temperature can be a problem.
A temperature monitor appears to be necessary and an error may occur if the temperature exceeds the recommended temperature shown in the hardware manual.

※ Opening the door to the casing may allow more air in, but it may not be enough to lower the GPU core temperature.

When I tested the CPU temperature a long time ago, I remember the difference as a temperature difference of 3 to 5 degrees.

Air cooling is also related to the temperature inside the room and the airflow.

  1. Please update the blender to version 4.5.4 of blender.
    (Please update the LTS version periodically. It is a version that provides stable, long-term updates.)

The update is currently in progress to version 4.5.5 of blender, and this version of testing is also available.