Visualizing the world space shading normals inside the TransmissionThinwallTestGrid.gltf model shows that all font geometry has normals which are not consistent with the background planes behind them (color = N * 0.5f + 0.5f):
The light green means the normals are (0, 1, 0) instead of (0, 0, 1) like on the background planes.
This can result in unexpected lighting results because the core material default for dielectric specular reflections is not black and would handle this view as Fresnel near 90 degrees which should produce unwanted reflections.
Visualizing the world space shading normals inside the TransmissionThinwallTestGrid.gltf model shows that all font geometry has normals which are not consistent with the background planes behind them (color = N * 0.5f + 0.5f):
The light green means the normals are (0, 1, 0) instead of (0, 0, 1) like on the background planes.
This can result in unexpected lighting results because the core material default for dielectric specular reflections is not black and would handle this view as Fresnel near 90 degrees which should produce unwanted reflections.