Point light with hard shadows creates NaN-like artifacts from distance (Deferred+, 6000.2.15f1)

[spring ore]

Alright, here's a weird one. Would really value any outside thoughts, as it's cropped up in a few projects now.
You can see it in action in the video down there. Here's some other fast facts:

• Getting close enough to the light results in the black tiles disappearing, and the light rendering normally.
• Tested with all post-processing and renderer features off - when checking in Frame Debugger, it indeed happens in the lighting pass.
• This project uses Deferred+ URP, but I've had this exact issue in Forward+ as well. Reproduced consistently across computers.
• The issue doesn't occur with Soft Shadows or No Shadows set. It only affects Hard Shadows.
• It happens in both Scene and Game view

[stark grove]

Does it occur with ordinary forward or deferred rendering paths
Have you been doing notable editor version upgrades

[spring ore]

Ah! Doesn't occur in normal deferred.

So there's probably something funky with the clustering

No major editor version upgrades. I did give it a shot on latest 6.3 LTS version, but it's still happening there too (Deferred+):

[stark grove]

And on forward+?

I would try to repro on 6.0 if it occurs there
6.1 through 6.3 have all been painfully buggy

[spring ore]

Yeah, forward+ too

Normal forward is fine

It's just the paths that do clustering. I'll give 6.0 a shot for the sake of completeness, but we'll likely keep to the standard Deferred path on our current Unity version until they fix it. It's a bummer how consistent this problem's been, I've been running into it for all of 2025 across multiple projects :(
I did look for an existing bug report of this but couldn't find it - do you happen to know of any off the top of your head?

Weird potentially-inconsequential wrinkle, when I disable HDR in the Rendering Debugger, it goes from black to like, this overlay

[stark grove]

I don't know of one, just seen clustering issues very commonly in the newer editor versions, and sometimes on 6.0 too
I guess it could also be related to graphics API and/or the specific hardware too

[stark grove]

Looks like expected shadow color on the right

[spring ore]

Mhm, just shaped super wrong. Still messing about in the render debugger, the clusters go red when Hightlight NaN, Inf, and Negative Values is enabled

[spring ore]

These are good shouts. I did repro on 2 separate machines, so it's still possible it's hardware-specific, but I'm leaning away?
Could be graphics API. Fwiw it's been happening all year and I've updated my graphics drivers yesterday to no change.

[stark grove]

Without HDR the shadow color is clamped to 0-1 so with HDR it's clearly outside of that

[spring ore]

Yup - and since it's the same broad behavior on and off, I doubt the problem is on that level

[stark grove]

I would make test builds of the repro using different graphics API, and see if it replicates there, and testing on more different machines
If I wanted to poke at it

Ultimately you'll just need a workaround, or a version where it works

Most curious that it doesn't occur with soft shadows
I was under the impression those are just filtered hard shadows so issues should be inherited

[spring ore]

Yeah, right? It's really strange.
I appreciate your thoughts! I think the workaround for now is just switching to standard Deferred.
Gonna try a few graphics APIs for the sake of building a case, and then I guess casting it into the abyss of the forum to see if it gets picked up by Unity as a bug.

[stark grove]

Best to report it as a bug directly
Bug reports are always checked by QA, forum posts worst case might not be checked by anyone

[spring ore]

Fair enough

I'll make a repro project and do that. Probably update this forum post a couple times just for my own bookkeeping, then merge it all together in a report.
Thanks!

6.3 D3D11 (same issue, but with flickering)