If I need to render a single object separately within a much larger scene, but needed the shadows, reflections, etc that it creates, to composite later in photoshop, how would I do that?
stick a VRPlane underneath your object and make it a matt object. (Do a search) If you need the shadows etc of the object to fall onto other objects in your scene, I usually just make blocks more or less the size of the objects and “matt” those also. This way your 3D object will cast shadows on the floor and on walls etc in your real scene.