distance field indirect shadows and self shadowing artefacts

Hello,

I’m struggling to set up distance field indirect shadows on a sofa in an archviz scene. I see this on other meshes as well, but it’s most obvious on this sofa.

The issue is very messy self shadowing on the mesh, and I can not figure out how to avoid it. One common observation is a brighter area along the top edges of the mesh and shadowed areas below (also visible on the table and the chairs.

To illustrate: settings for the mesh in this screenshot:

  • distance field resolution scale: 100
  • distance field self shadow bias: 0 (but no value >0 fixes the problem)
  • distance field indirect shadow min visibility: 0.5

280398-uegenerateddf.gif

Seeing that the self-shadowing does not cover the whole mesh I tried using a Distance Field Replacement Mesh of very simplified geometry, but blown up a little to extend beyond the original mesh all around, hoping the self shadowing will at least be even. Here is the result of that. (same settings as in first test). Obviously the problem is less grave, but my replacement mesh needs to be tweaked to have enclose the sofa more evenly:

280399-dfreplacementmesh.gif

And here is the result with distance field self shadow bias set to 20:

280400-selfshadowbias20.gif

If the replacement mesh was constructed to really cover the whole mesh evenly, would this really the best fix for the problem?
Is my scene not set up correctly?
Do I need to adjust my lighting setup?

Looking forward to some pointers.