Virtual Shadow Maps with spiky edges for low poly mesh but no normal maps

[CsSpacePenguin]

With virtual shadow maps (and all global illumination turned off), I have the following shadows on my planet geometry:

Shadow mask view:

The documentation mentions that low poly geometry with smooth normals can cause something similar to this (“shadow terminator problem”); however, I don’t even have a normal map attached.

World normals view:

What can I do to resolve this?

Documentation comment (unless I’m misunderstanding the root cause):

Low poly geometry with high curvature and smooth normals can exhibit artifacts. This is known as the “shadow terminator problem.” It also occurs in ray tracing and other highly accurate visibility queries. The issue stems from the mismatch between the real low poly geometry and the “smooth” shading normals

Which can be found from: Virtual Shadow Maps in Unreal Engine | Unreal Engine 5.4 Documentation | Epic Developer Community

Thanks for the help!

[CsSpacePenguin]

So I realized Unreal might be interpolating normals (e.g. from the vertex) and that can be a source of smooth normals.

I decided to enforce flat normals by creating a test material with a flat normal map:

It did improve the intensity of the edges, but they are still a tad visible if you look closely (middle halflit triangle and one of the triangles on the right):

The shadow mask is still ugly:

If anyone knows how to further improve this, that would be great, thanks!

[BananableOffense]

The only answers when not using a normal map are to increase the poly count of the mesh, or add a bias to the shadow. You could alter the geometry for a specific object in the shadow using the shadow pass switch node in its material, or there is a cvar that controls shadow bias for all VSM shadows.

Terminating the Shadow Terminator Problem (Jagged Shadows)