Let's say I have a scene to render in cycles, and one particular area needs a much large sample rate to achieve satisfying render result. I would like to render the scene in normal sample rate (say, 150), and then I come back to render that particular area with a much higher sample rate (like 500 or higher) with an animated mask so that blender would only render that area. I know there's a mask layer thing in blender but that doesn't stop blender from rendering the whole scene first. I needed something like the render area crop, only animated. Is it possible?