Small cone angle lowers VSM resolution

Development Rendering
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1

We have noticed that VSM shadows lose resolution not only when the cone angles becomes larger (which makes sense to me) but also at a very specific low value.

Is there a change to a lower resolution shadow map under a certain value for the cone angle? Do we have any control over it?

In some specific cases we would need to still have a lot of resolution, even for very narrow lights

2

Steps to Reproduce

  1. Create SpotLight in empty map
  2. Use VSMs
  3. create a plane and any other mesh (a sphere in our case)
  4. place the light 1400 units above the plane
  5. set the cone angle to small values
  6. see as the shadow resolution lowers at a very specific value
3

Hi there,

This is a known issue within 5.4 - 5.6 and in extreme cases, can cause the VSMs to invalidate every frame.

Spot Lights may present with very blocky shadow artefacts when a long attenuation radius is provided with a small cone angle

This is targeted for fix in 5.7 Here is the public issue tracking link for more information: Unreal Engine Issues and Bug Tracker (UE\-290280)

Kind Regards

Keegan GIbson