Virtual Shadow Map Blocky Flickering UE 5.3.2

[olegwer1 (Oleg Verenko)]

https://youtu.be/Knlis2jOzZw
An interior scene. Same on the viewport and Rendering. When I change shadows to ‘Shadow Map’ mode - there is no flickering. I tried to increase Lumen samples - no effect. Any idea how to keep a virtual shadow map without this flickering? UE 5.3.2

[brs-sebascova]

Hello there @olegwer1!

Checking through the community for similar scenarios, there are a few parameter changes to test around. From your light’s source details’ panel, adjust the following:

• Shadow Map Channel: set to 0

• Shadow Map Resolution Scale: switch between 2.0 to 4.0

• Virtual Shadow Map Bias: go from 0.01 to 0.1

• Normal Bias: switch between 0.2 to 0.3

• Dynamic Shadow Distance Movable Light: increase to 20000

• Also, it is always useful to update UE to the latest, stable version (these days, either 5.5.4 or 5.6.0 will do the trick), as well as setting your video drivers to the developer version.

• Finally, check the thread and documentation below for more methods to test:

Improving Virtual Shadow Map Distance/Quality

Hello all. With virtual shadow maps, I’m having trouble getting detailed shadows to stay visible as I move the camera further from mesh geometry. This is just with a single directional light, movable. [vsm_pop] As this picture tries to show, moving a slight distance forward towards this mesh results in a much more dark and detailed shadow appearing under the bricks. That’s working as intended, I understand, as part of the clip map system. However, I’m just a little confused as to how close yo…

Virtual Shadow Maps in Unreal Engine | Unreal Engine 5.6 Documentation |...

[sarahlenker]

To add on to @brs-sebascova’s answer,

This could also be due to a physical page pool overflow- or when the number of cached pages exceeds the max page limit. You can use r.ShaderPrintEnable 1 and r.Shadow.Virtual.ShowStats 2 to debug and see if this is your problem. If it is, you will need to either decrease your number of shadow-casting lights, decrease the shadow resolution, or if you aren’t too worried about performance you can increase the maximum page pool size with the command r.Shadow.Virtual.MaxPhysicalPages

[olegwer1 (Oleg Verenko)]

Yep, the project contains a lot of spotlights with a big attenuation radius to simulate volumetric fog.
Decreasing the number of lights helps in my case.

[seanspitzer]

(post deleted by author)

[seanspitzer]

[quote=“seanspitzer, post:5, topic:2562800, username:seanspitzer”]
Also you could try experimenting with MegaLights to help some of the workload. This maybe okay if you are not shipping a game since it’s in it’s early development. NOTE: It’s used for all lights except the Directional Light, and Skylights - (Analytical lights only). You may get hit on shadow quality with a large amount of lights. - Things to Note:

MegaLights can cause hidden shadows to disappear, only becoming visible with a path tracer.

Screen space traces used by MegaLights rely on Scene Depth and will hit anything visible on screen. This can cause issues with invisible shadow casters that only exist in the Ray Tracing Scene and don’t affect Scene Depth.

[olegwer1 (Oleg Verenko)]

I am using UE 5.3.2 (for FAB).
Looks like there are no MegaLights in this version…