Using the final film resolution, drag select an area on the render and Octane would render just that tiny bit instead of the whole film. This way we could prototype suspicious areas (such as DOF, noise, caustics) and get fast feedback on supposed final quality. There is nothing more wasteful than a few hours of rendering, just to discover that DOF is too strong / noise won't clear as you thought it would / texture scale doesnt look as good as in test renders, and other stuff you can't notice unless you render the scene in final res for a considerable amount of time.
With border rendering option we could assess render quality very fast and in selected areas. With all the interactive nature of Octane, this is a must-have.
Can we have it? Pretty please
