Render Bucket Orders

Lots of CPU-based rendering programs feature a selectable bucket-order (and bucket size) to let users control how their image is rendered. Some users like to render from the center of the image outwards (Spiral bucket order) because the center of their image is the most important and they need to see it first, some users like the most memory-efficient method (Hilbert), while others like random chunks rendering across their image to get a good view of different areas of the image at once.

Users with less powerful machines also benefit from smaller bucket sizes because certain difficult buckets can get divided among multiple cores instead of being assigned to a single core.

I know about the zoom-to-render function we have now, which is nice and I use it every-so-often myself. It's just one of those things I notice about FF that keep it in the "Old programs" category. It's not important I just thought I'd drop it off here.