Fade local light shadow with r.Shadow.DoesFadeUseResolutionScale not working

Development Rendering
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<br>In response to this feature request:

[Content removed]

Epic provided new code in CL 38507345 which exposes a new CVar which is supposed to give greater control with respect to fading shadows from local lights.

In my attempts to test it with different Shadow Resolution Scale values, I was not able to achieve any fading of the shadow, only on/off with popping.

Am I missing something in my light setup?

Are there other ways to fade shadows independently of the light’s Max Draw Distance/Fade Range?

Thank you

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Steps to Reproduce

  • Get CL 38507345 (ola.olsson) that exposes new CVar r.Shadow.DoesFadeUseResolutionScale.
  • Create an new map with floor, a spotlight, and a cube
  • Set spotlight to various Shadow Resolution Scale values
  • Observe that shadows do indeed cut off past a certain distance/screen coverage but never fade
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Hi,

I’m having trouble replicating the shadow popping issue in your video in UE 5.5.4. In my test project, both the spotlight and shadows disappear when the camera is at a certain distance (the shadow resolution scale is set to 0.2). Would you mind sharing a minimal repro project?

I have not been able to test the r.Shadow.DoesFadeUseResolutionScale yet, but looking into it.

Thanks,

Sam

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Hi,

I wasn’t able to find CL 38507345 in the Unreal Engine Github repository (which usually mirrors the CL). After asking around, it seems that this CL is part of the Fortnite branch, which I don’t have access to. I will re-assign the case back to Epic, who can investigate this further.

It would still be helpful if you are able to provide a minimal repro project.

Thanks,

Sam

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The corresponding change in //UE5/Main is CL#38507350 (ff88592), taking a look to see what’s going on.

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I’ve verified that local shadow fading doesn’t appear to work with Virtual Shadow Maps, though it does with CSM. The FadeAlphas don’t appear to be passed used when VSM is used, and I tested with one pass projection on and off and neither seemed to make a difference. I’ve created the following issue for tracking which should be visible soon. https://issues.unrealengine.com/issue/UE-275317

If you want to see how they should work, switch to regular Shadow Maps and adjust the r.Shadow.MinResolution and r.Shadow.FadeResolution which are the resolutions between which the shadow should fade out. You may also want to adjust the r.Shadow.FadeExponent to control the rate of fading.

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Hello! We don’t have a fix version assigned yet but at this point the default will be 5.7, but I’ll request it be integrated to a 5.6 point release if possible.

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Thanks for confirming!

I realize it’s quite fresh but would you already happen to know which release this fix is targeting? Otherwise I will be checking UE-275317 from time to time to see its progress.

Thank you.