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EEVEE shadow rendering errors
Closed, InvalidPublic

Description

System Information
Operating system: Windows 10
Graphics card: GTX 1080 & 1050Ti

Blender Version
Broken: blender-2.80.0-git.a7c5f4f20657-windows64

Shadow computation error when rendering with EEVEE. When two polygons touch there is light bleed-through in the shading computation which should not exist.

Open default scene.
Delete nearest vertical faces of default cube.
Render with EEVEE using F12
Upper edge of left rear face of cube receives illumination where it should be in shadow. Leaking illumination around right rear face of cube. Odd hard-shadow artifact on lower face on front edge.


I suspect this is due to edges being evaluated in different directions during the render, so there is an apparent gap where there isn't actually one in the topology of the object.

Renders correctly in Cycles or Blender 2.79 "Bender Render"

Details

Type
Bug

Event Timeline

Not a bug. Those are the limitations of real time z depth shadows, since they are not raytraced. Very common in videogames.

You can get better results, but not out of the box until you tweak some values, turn things on or off, and make a trade between performance and precision. Here are the things you can do:


-Use geometry with thick walls instead of thin. Like if you make an interior, make sure to surround it with thick walls
-Change ESM shadows for VSM shadows (located in the render settings)
-Increase shadow resolution and use high bitdepth (render settings)
-Decrease Softness on each lamp close to 0 and turn on Soft shadows in the render settings instead
-Decrease Bias close to 0 (per lamp setting). If you're using VSM, increase Bleed bias too
-Use contact shadows

I personally go for VSM, Shadow res = 2048 or higher, High bitdepth = on, Soft shadows = on, Softness = 0.3, Bias = 0, Bleed bias = 0.5, and Contact shadows = off, since they are screen space and weird with thin occluding objects

I'll close this then.