Hi everyone,
I’m running into a strange shadow issue in Unreal Engine 5.6 using Lumen + Virtual Shadow Maps.
The problem
Only half of my stairs receive proper shadows.
The lower part of the stairs looks correct — every step has clear shadow definition.
But starting from the middle upwards, shadows suddenly disappear and the stairs look completely flat/lit, even though:
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The geometry has real height, not just a normal map
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The material is Default Lit
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“Cast Shadows” is enabled
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“Virtual Shadow Maps (Beta)” are active globally
If I rotate the sun, the shadowed area swaps sides — so lighting works, but shadow coverage cuts off halfway around the arena.
Scaling the whole Colosseum smaller does not change anything.
What I’ve already tried
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Verified Virtual Shadow Maps and Nanite Shadows are enabled in Project Settings
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Recreated a new Movable Directional Light (to reset old CSM buffers)
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Tweaked Shadow Bias / Normal Bias (0.3) → no change
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Increased r.Shadow.Virtual.MaxPhysicalPages, r.Shadow.DistanceScale, Lumen Scene Extents → no visible effect
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Contact Shadows ON (0.5 length)
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No lightmap UVs, no baked lighting
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Shadows render fine under the stairs, but not on top
There are no shadows on the left half of the image because it is in direct light. If the sun is at a 45 degree angle, and points at a stair step, it will equally light both the horizontal and vertical surface and no shadow will be seen.
If you change the angle of the sun so it isn’t hitting the top and side evenly, you should see more distinct shading but still no cast shadow.
If you don’t, you should inspect the world normals of your mesh and ensure they are correct. Incorrect normals are the most common reason for improper shading.
no that isnt it. if i change the direct. its still only half. my normals should be fine as well 
You are referring to the left half of the image, are you not? If so I can easily find real photos of amphitheaters where this exact same behavior exists. Here’s an example:
No shadows on the left. The main reason your image looks off is that it has one large texture stretched across the surface, so the shadows are the only thing creating any perception of detail. Therefore without the shadows it makes it look like one uniform surface. Whereas in the above reference, wear and tear on the edge of the seats/steps creates a perception of detail even when shadows are not visible due to the angle of the light.
