Stain in volume light

Hey,

A few things to consider, apart from the usual "Filter" checkbox and increasing the quality of the effect ("High Quality" checkbox in the HDRP asset for pre-HDRP9, or tuning the slices for HDRP +9):

0. The technique HDRP (and now many other games) use is somewhat more prone to flickering because the voxel grid moves with the camera frustum (froxel). It isn't a world-space grid.

This also means that using a point light (with a cube map cookie) is a lot more suited to such technique than using a spot, as the spot light will make such artifacts more obvious, as the light is only shining in one direction, whereas a point will hide most flickering artefacts.

1. In the camera's Custom Frame Settings, enable Reprojection (under Lighting > Fog > Volumetrics). This will greatly improve the quality and stability, but in Play mode only, NOT in the scene view!

2. Increase slightly the "Radius" of the light (Radius != Range). This will greatly mitigate the "hotspot" your see near the light source.

3. Play with the slice distribution uniformity in the fog volume component: lower value will give more precision closer to the camera.

4. You should try to build your lamp with an actual light bulb or emissive surface. This will indeed hide some of the flickering, as that space will be occupied by a piece of bright geometry (and some resulting bloom).

5. You need to understand that if you want an incredibly strong volumetric effect only from the lamp, it isn't really physically plausible if you don't have a very thick atmosphere in this room already. And I reckon this is probably the root cause of the issue you're seeing (apart from having a near-0 light radius).

I suppose you're probably using a very high light intensity and/or a very high volumetric multiplier: I see you're using a volumetric multiplier of 10 in your first video! This means you're pushing the system way further than expected, and you somehow expect the volumetric effect to be 10x stronger than the amount of lighting than the light emits. So you should expect some artifacts indeed, as you're breaking some rules here.

With more conservative settings, a proper light bulb, and reprojection activated, the volumetric effect is actually surprisingly smooth and stable. Keep in mind however that if you start pushing the effect beyond physically-plausible value by using an incredibly high volumetric multiplier, it will worsen the look of the effect.


(many people are on holiday at the moment, so longer response time can be expected)