Jitter/Instability on Point Lights near Alpha-Tested Geometry (Vegetation)

[OndrejPetrzilka]

Description:
When using Volumetric Fog with Point Lights, there is significant temporal instability ("boiling noise") near high-frequency depth edges, such as alpha-thresholded vegetation. The noise pattern appears to crawl across the screen even when the camera and light sources are completely static.

Observed Behavior:

• Visible jittering in the light volume.
• The artifact is most pronounced where the light volume overlaps with complex depth (foliage).
• The noise pattern cycles/moves continuously.

Proposed Solution / Feature Request:

1. Static Jitter Seed: Would it be possible to lock the jitter seed when the camera and scene are static? If there is no movement, the raymarching offset should remain constant to prevent "crawling" artifacts.
2. Depth-Aware Upsampling: The jitter is probably exacerbated by the upsampling process. Implementing a bilateral upsample (potentially using a 3x3 tent filter approach similar to the Jimenez/CoD Bloom implementation) might help the fog respect the edges of alpha-tested geometry better.
3. Karis Weighting: If the jitter is caused by high-intensity specular "fireflies" within the volume, a Karis-style weighting during the accumulation phase might stabilize the result.
4. Temporal reprojection: Maybe you already plan to address this with reprojection.

Environment:

• Unity Version: 6.4
• Asset Version: 0.5.9

Attachments:

unknown_2026.04.20-15.47_clip_1.mp4

[CristianQiu]

Thanks for the info, this is pretty interesting testing set-up.

Could you try the dev branch? I actually have working reprojection there and I would like to see how it behaves in comparison.
In any case I'll try to set a similar test scenario when I can, I want to release the dev branch at some point but I would like to make some improvements first (it should have similar reliability to v0.5.9 though)

[OndrejPetrzilka]

The issue is mostly visible in Scene View for some reason.
In GameView (play mode) it's much much less noticeable. Reprojection helps in a way that SceneView is now consistent with GameView 😃

I think the GameView "issue" is just not enough samples. Increasing sample count to max helps.

[CristianQiu]

Maybe you are using TAA , which doesn't work in scene view and may slightly help diminishing the fireflies in gameview. Could be due to much higher FPS on the game view too. Other than that, I can't really think what would make it mostly visible on sceneview but not on the game view. But yeah, in v0.5.9 you should aim to have raymarch steps to be in between x2 - x4 of max distance IIRC for best quality in these kind of demanding scenarios.

Funny thing is that because the scene view does not have correct motion vectors, reprojection isn't really working properly either in dev branch :) I also did a small test with vegetation and reprojection certainly makes it better in the gameview too.

So to sum up, as of 0.5.9 play adjusting distance/steps, however the update with reprojection will make it better :)