Masked Materials do not Function with Nanite Meshes in 5.8 preview if Vertex interpolator is present

Development Rendering
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See repro steps

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Steps to Reproduce

  1. Create a new material.
  2. Set Blend Mode to Masked
  3. [optional] enable use Material attributes
  4. Set something up to output to opacity mask & base colour. I.e a texture with an alpha channel
  5. important: Tick ‘used with nanite’
  6. important: place a ‘Vertex interpolator’ node in the material graph, it doesn’t need to be connected to anything.

Apply the material to a mesh

  1. copy the basic sphere mesh to content folder (/Engine/BasicShapes/Sphere.Sphere) or source some other static mesh
  2. Set the Material on the mesh
  3. observe that if the mesh is set to use nanite, the mask will not function.
  4. observer that if the vertex interpolator node is removed, it works.

5.8 preview, repro project attached

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Hi! This should be fixed in CL 54931849. It didn’t make it for 5.8 but we’re looking into having it in 5.8.1

https://github.com/EpicGames/UnrealEngine/commit/89dcc1cc6ed3accb53e116a4668fe3158793e582

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