Visual Artifacts from Distance Field and LOD

Development Rendering
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1

Hello,

Since updating to 4.9 we’ve had a pretty significant bug exacerbated by the interaction of our distance field lighting and LODs. On many of our meshes once the mesh increases above LOD0, the mesh gets severe, extremely dark shadows on the mesh - presumably due to the lower resolution LODs being slightly smaller than the base mesh, but the lower resolution meshes appear to be using the distance field meshes for the larger size base mesh.

This bug existed in 4.8 but we were able to mitigate the effects somewhat by increasing the Occlusion Max Distance in the skylight, however this no longer appears to have an effect.

Setting the ‘Ray Start Offset Depth Scale’ in the Directional light reduces the artifacts on SOME of the meshes, but other, meshes are completely unaffected.

Increasing the build scale of some of the LOD meshes to 1.010 - 1.015 can fix it for most meshes, but concave areas still receive the bad artifacts.

Is there anything that can be done about this?

2

Can you post a screenshot to demonstrate the issues you’re seeing?

Does this only happen on certain meshes, or any mesh?

Thank you!

Tim

3

Hello Tim, as far as I can tell it happens on any mesh where any LOD above 0 has geometry smaller than the base mesh

LOD0

57202-lod0.jpg
57202-lod0.jpg1180×957 352 KB

LOD1

57203-lod1.jpg
57203-lod1.jpg1180×957 236 KB

4

Hi Luke,

This is a limitation of shadowing using distance fields. The base LOD will always be used, even if there are lower LODs.

You can see this in the Show > VIsualize > Mesh Distance Fields view mode. As you move away from the mesh the lower LOD does not have a distance field. This is a feature that may be added in the future, but currently is not implemented.

For meshes that this is an issue with you can disable the option for “affect distance field lighting” in the details panel for each mesh.

Thank you!

Tim