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Volumetric lighting leaking in eevee
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Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: Radeon (TM) RX 470 Graphics ATI Technologies Inc. 4.5.13559 Core Profile Context 26.20.12001.11014

Blender Version
Broken: version: 2.82 (sub 1), branch: master, commit date: 2019-10-28 21:19, hash: rB2dab4393b08e
Worked: (optional)

Short description of error
Volumetric lighting is visible through thin geometry if a light is placed close to it. Effect is especially bad if the light is inside an object. In this example there is a spot light inside the cube on the left. Both object have a simple opaque material.

Event Timeline

attach the blend file, so we can do immediate tests

Ok, here it is. But there's nothing special about this file, it's just a bit modified startup scene.

I just tried opening this scene in 2.80 and it looks a bit better. Basically the light leaking appears only when the camera is at a specific distance from the object in front, but in 2.81 beta and up it's always visible. So maybe it's related to the shadow system refactor.

It might also be because the volumetric samples are distributed closer to the camera ?
I've had issues with that before and turning the "Distribution" value in the "Volumetrics" settings down a little worked well in 2.80, seems like it doesn't fix much anymore since the shadow refactor.

We could also have a shadow bias exclusively for volumetrics (or maybe i'm just speaking gibberish)

Clément Foucault (fclem) changed the task status from Unknown Status to Unknown Status.Nov 3 2019, 12:19 AM
Clément Foucault (fclem) claimed this task.

I think this was a side effect of a previous bug (in 2.80). basically, the volumes were all shifted 1 voxel further from the camera. This was fixed but now this light leaking is just a side effect of the volume texture being low res.

There is little we can do to fix it. The workaround is to give more precision to the volume (increase samples in volumetric settings) and the shadow maps.

16/08/2020
Blender 2.83 still has this bug :((

16/08/2020
Blender 2.83 still has this bug :((

As Clement has already stated, this is a sort of precision error.
This probably won't be fixed anytime soon.
Unless a new groundbreaking volumetric lighting approach is discovered, which is... quite unlikely?

You can attempt to alleviate this by making the volumetric lighting texture more fine.
This will however use more VRAM so be careful

You can attempt to alleviate this by making the volumetric lighting texture more fine.
This will however use more VRAM so be careful

Thank you for the answer. But seems like for me in versions 2.81 and higher nothing really changes when I try to tweak ANY mentioned option (distribution, samples, tile size, shadow samples). Only in 2.80 it can help sometimes :'(