Farfield shadow in lumen scene

Development Rendering
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1

Hi,

I am trying to understand the behavior of the shadows in FarField.

In this example (CitySample), I am forcing the Lumen scene to be as small as possible (r.RayTracing.Culling.Radius 1000) to see the Farfield tracing as close as possible to the camera.

You will notice in the video that shadows from certain building persist even quite far where some others will completely disappear when leaving a close perimeter.

I am not sure what is causing that, and I would like to know if there is any way to prevent an asset to get their shadow culled out from Farfield.

I have tried to play with the RT group priorities but that doesn’t seem to work.

I am currently working on a cave setup and distant (farfield) shadowing/occlusion is crucial.

I would not be able to share my scene, but the CitySample is highlighting my problem well enough. Currently it looks like the FarField in the cave let quite a lot of directional light to leak through which compromise the occlusion.

Also, when the culling radius is small, it seems like all local fog are also getting lots of light info from the directional light. It doesn’t seem like Farfield is able to occlude the light received by the local fog. Is this expected?

Thank you

2

Steps to Reproduce

  • Use CitySample small level (5.5)
  • Load all streaming region if not done yet
  • Make sure HLODs are enabled from the ‘‘show’’ menu
  • Use the cvar r.RayTracing.Culling.Radius 1000 to significantly reduce the lumen scene
  • Display the Lumen Scene
  • Notice Farfield is now very close to the camera. This will help highlighting the issue described.
3

Hello,

Thank you for reaching out.

I’ve been assigned this issue, and we will be looking into Lumen Farfield shadowing for you.

4

Hello,

Thank you for your patience.

We have reproduced the issue, and are still investigating.

5

Hello,

Thank you for reporting this.

I can confirm this issue can be reproduced as described in the latest CL, and have opened a bug report.

We will reply with the public tracker when it is available.

6

Hello,

You can track this issue here:

The tracker will be visible after it is approved internally at Epic Games and is publicly accessible.

If you have any further questions, please let us know.

7

Thank you for confirming this is an issue and not a user error.

Apologies for the delay getting back to you!

8

Hello,

Thank you for the reply.

Can we now close your case? You can always re-open it if you find you need additional assistance with the same issue.

9

Happy for you to close this case.

Thank you