Unexpected transparency in alpha map from RenderTarget

I’m using a RenderTarget to generate a simple alpha map using a Cylinder. The Cylinder uses a basic material with color white, which should be fully opaque in the alpha map, per the docs. However, when applied to a geometry, the area corresponding to white in the mask is not fully opaque, as shown in this react-three-fiber example:

The scene setup is:

  1. Red plane masked to a cylinder via the alpha mask - expected to be fully opaque
  2. Behind that, a white box - it should not be visible at all from default camera position, but it is.

Anyone have any insight as to why the white alpha mask leaves the Red plane with non-zero transparency (i.e. NOT fully opaque)?



Linking back to this issue on GitHub which has the solution/explanation to this issue (tone mapping defaults in the RenderTarget):

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