I discover something weird a while ago.
I have a scene all made with the new Physical Material shader and when for an object which I need to use as a backplate in my scene I turn off “Produce and Receive shadows” from it’s properties menu some weird shadows effect occur! Look at my example I post here. The shadows are produced (which they shouldn’t) and part of them are missing.
Make a plane and apply the new Physical shader.
Make a box on it, you can also leave it without material.
Open it’s properties and turn off Produce and Receive Shadows.
Put a Sun or HDR and render…
I don’t get the weird shadows break up of the shadows, maybe best if you upload that scene.
The appearance of the “shadow” seems related to the Roughness and IOR of the Base layer, changing those changes the results, in case that adds to the picture of things. An IOR of 1 gives no shadows. And a Roughness of 0 with max IOR of 3 (this is a non-metal) also gives no shadows.
@Dionysios so I am getting exactly the same results with the physical and legacy material. Please check my attached render and scene.
My guess is that you simply did not enable glossy reflections for the legacy material in your tests.
This is definitely one of the light transport issues from https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180
