The cube map is dynamic. We’re rendering a “real time” cinematic as a 360 spherecap.
So our workflow is to preview everything in real time. And then render it for the capture.
Because there are so many artifacts in most reflection schemes, I’m replacing reflections with a cube map captured from the camera location. So it’s updated every frame during the capture.
Mips does look like it will work. Maybe not quite as blurry as I’d like, but good enough. 