I'm attaching two screenshots of a render of a room with the floor missing to be filled with live action. Cleary, a good alpha channel would be helpful. In many recent renders I've found that the alpha channel has expanded, encroached, over the CGI wall that is supposed to meet the live action floor very precisely. Octane is rendering the wall correctly and it displays correctly (well, almost --there's often a weird jagged edge), but the alpha channel is creating a gap between the wall and the floor.
If you look carefully at the screenshots you'll see the bottom metal piece is narrower in height in the alpha render.
Please explain what is causing this and how to re-do these renders without the alpha expansion, thanks --Hal