UE 5.6, MetaHuman, Lumen + VSM…
I have a shot where one side of my MetaHuman’s face is in shadow. In the shadowed area, specifically on the cheek and side of the nose, there is a whitish/plastic-looking splotch. The splotch is caused by one specific rect light in the scene.
I have spent significant time diagnosing (thanks Claude) and have ruled out the following:
- Subsurface scattering — adjusting Mean Free Path Distance, Extinction Scale, and Normal Scale in a duplicated SSP_skin_unified asset had no effect
- Specular — setting Specular Scale to 0 on the light visibly affects the face but the splotch remains unchanged
- Indirect lighting — setting Indirect Lighting Intensity to 0 on the light has no effect
- Shadow bias — cranking Shadow Bias and Shadow Slope Bias to extreme values had no effect
- Light/head position — the splotch only disappears when the light or the MetaHuman’s head is moved 20-40 degrees from the intended position, which destroys the shot
The splotch definitively disappears when Cast Shadows is turned off on that light, confirming it is shadow-related. It also disappears when Ray Traced Shadows is enabled on that light, but this breaks volumetric fog god rays elsewhere in the scene so is not a viable solution.
All other rect lights in the scene with identical settings do not produce this artifact from other angles. The problematic light is at a raking angle to the face, consistent with cinematic side lighting.
Has anyone seen this specific artifact and found a fix? Thank you!
