Description

A material with Shading Model set to Subsurface Profile is no longer affected by Opacity value in 4.17, 4.18, and 4.19 (Main) but was previously working as intended in 4.16.
This is a regression.

User description:

"Setting a material to subsurface profile causes it to stop respecting the opacity value when applying subsurface scattering.

Repro steps:

Create a subsurface profile material with a valid subsurface profile. Assign to a mesh and place the mesh under a bright point light Assign a constant of 0 to the opacity input of the material, and note the appearance of the mesh. Assign a constant of 1 to the opacity input of the material, and note the appearance of the mesh. There is no difference.

Because of this bug, it is impossible to mask the subsurface effect to limit it to only parts of the material."

Steps to Reproduce
  1. Open attached project with UE 4.16
  2. Load 'OpacityTest' Map
  3. In Viewport 'View Mode' > Buffer Visualization, select Subsurface Color. Note that the sphere on the left with 'Skin0' material (Opacity value= 0) is completely black, and sphere on right with 'Skin1' material (Opacity value= 1) is dark red.
  4. Also open 'Skin0' and 'Skin1' in Material Editor and notice the visible difference ('Skin1' is lighter, more neutral than 'Skin0')
  5. Now, open the project in UE 4.17 or 4.18
  6. Load 'OpacityTest' Map
  7. In Viewport 'View Mode' > Buffer Visualization, select Subsurface Color. Note that now both the right and the left spheres are shown in dark red.
  8. Also open 'Skin0' and 'Skin1' in Material Editor and notice that both materials now look identical.
    Result: Opacity input channel no longer has an effect on material with Subsurface Profile
    Expected: Opacity input channel will affect material with Subsurface Profile

Have Comments or More Details?

Head over to the existing Questions & Answers thread and let us know what's up.

2
Login to Vote

Fixed
ComponentUE - Rendering
Affects Versions4.17.24.18
Target Fix4.19
Fix Commit3743621
CreatedOct 24, 2017
ResolvedNov 8, 2017
UpdatedApr 27, 2018