I've attached a project with the necessary materials that demonstrate this issue. I would expect that just because a Set Material Attributes node is inside a material graph it wouldn't affect the decal blend mode of the material.

Steps to Reproduce
  1. Create a new material, set its domain to Deferred Decal, and its Blend Mode to Translucent.
  2. Check the "Use Material Attributes" checkbox
  3. Create a Set Material Attributes node and expose the Normals and Opacity pins
  4. Connect to the Normals pin this texture: Texture2D'/Engine/Functions/Engine_MaterialFunctions02/ExampleContent/Textures/newhplaneNormalsMap.newhplaneNormalsMap'
  5. Connect a SphereMask to your opacity pin: 
    [Image Removed]
  6. Create a new Set Material Attributes node that takes the Normals/Opacity Material Attributes as an input, and expose the Base Color pin. 
  7. Create a new Vector Parameter named "Base Color" to the Base Color pin and set its value to 1.0, 0.0, 0.0, 0.0.
  8. Connect the output of this Set Material Attributes to the Material Attributes input pin.
    [Image Removed]
  9. Create a new child instance of your material and apply it to a new Decal Actor.
  10. You should now see the decal affect the scene as expected.
    [Image Removed]
  11. Duplicate your decal material, and in this one connect the Normal/Opacity Set Material Attributes to the output of the material. You should leave the Base Color Set Material Attributes node in the material but disconnected from the flow of the material.
    [Image Removed]
  12. Create a new instance of your Normal/Opacity decal and apply it to a new decal actor.
  13. You should now see the decal apply a black base color instead of using the underlying base color of the surface it's applied to.
    [Image Removed]
  14. Finally, duplicate your Normal/Opacity decal material and delete the Base Color SMA from the graph. 
    [Image Removed]
  15. Create a new instance of this base colorless material and apply it to a new decal actor, and observe the expected behavior. The decal modifies the normal of the underlying material without affecting the base color.
    [Image Removed]

Have Comments or More Details?

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-129565 in the post.

Login to Vote

ComponentUE - Graphics Features
Affects Versions5.05.1
Target Fix5.5
CreatedSep 28, 2021
UpdatedJan 18, 2024