Stationary lights breaks shadows if source length > 100

Development Rendering
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1

Hi,

stationary point lights create wrong shadows on movable/stationary objects if light source length exceeds a value of 100 (after bake). See gif for a better understanding. Why is that so (by design or possibly a bug)?

265021-statshadow.gif

Besides this, i still wonder how stationary lights create shadows. These shadows are obviously different from movable lights but both write to a shadow map. Where is there difference in detail? Did i understand it right, they are creating shadows by generating distance fields (even when distance fields are disabled in project) and use this volume information to render a shadow map (according to this: https://docs.unrealengine.com/en-US/Engine/Rendering/LightingAndShadows/LightMobility/StationaryLights )?

regards guys

2

Looks like shadow problem is due to the source intersecting with the mesh with 0 radius. It can handle some intersection but it becomes more obvious when more than a quarter of the light source is intersecting. Increasing the Source Radius can help.
I’m not sure how stationary lights calculate shadows but the most obvious difference from static lights is that stationary lights cast dynamic shadows for dynamic(movable meshes or skeletal meshes) objects.