Additive scene capture produces corrupt texture on Mac/iOS

Hi, since at least 5.1 additive scene capture results in corruption on the render target, seemingly only under the Metal renderer (Windows/DX doesn’t have this issue).

Steps to repro:

  1. Create a new blank game project, blueprint-only, so the editor loads into the open world map (just so you have something to capture)
  2. Create a render target with default settings
  3. Drop a scene capture 2D actor into the scene
  4. Set the scene capture’s texture target to the render target from step 2
  5. Mouse over the texture target thumbnail to make it update, you’ll see it looks fine
  6. Set the scene capture’s composite mode to Additive
  7. Mouse over the texture target thumbnail again (or open the render target asset) - the texture is now corrupted


I tried to put a bug in about this but the bug reporting system just gave me a spinner for > 5 minutes - so if my friendly local Epic support staff can repro it and put a bug in for me I’d be very grateful!