Hair Shadows Not Affecting SSS Back Scattering (Subsurface Profile)

Groom strands do not appear to correctly block transmitted light for Subsurface Scattering Profile Materials. In some cases, not only will they not block the light, but can instead lead to more light being transmitted.

GPU captures show that there is some level of calculating the shadows from the Groom, but it does not appear to be properly blocking transmittance. The "Shadow.Denoiser.DenoiserOutput0" texture shows the shadow correctly in the R and B channels (the "FadedShadow" factor from SSDSpatialAccumulation.usf), but only partially affecting the G and A channels (the "FaddedSSSShadow" factor).

1. Download the Licensee's test project and open (see addl info URL)

2. Open the map "/Game/DebugShdHair//Game/DebugShdHair"

3. Observe the flattened cube "Cube" from the front (the side with the light shining on it).

4. Observe the Groom hair and the cylinder are both casting shadows on the cube.

5. Observe the flattened cube "Cube" from the back

6. Observe only the cylinder is blocking transmitted light.

7. On the RectLight "RectLight", reduce the intensity to 0.5 EV

8. Execute the console command "BugItGo -4.892847 104.002888 198.884167 3.357953 -82.364467 0.000000" to line the camera and light up through the cube.

9. Move the Groom "GRM_Hair" left and right in the X-axis (without moving the camera)

10. Observe that a slightly brighter portion of the transmitted light appears to be where the groom is, while moving across the brightest area of transmittance.