[REQ] Render only a portion of an image

[Dusan]

It would be very useful if it were possible to render only a certain (e.g. rectangular) portion of the entire image.
In case when just a small detail in the scene was changed, it wouldn't be necessary to re-render the entire image again.
Thanks.

[Kram1032]

It would be useful for showing bugs, yeah, but for what you're saying, it wouldn't be that useful, I guess:

what about the radiosity in diffuse materials?
what about the reflections?

It depends, *how* small the change is, for sure, but usually, if you don't want to show a special bug, rerendering the whole thing should be better

[Dusan]

I understand your point, on the other hand there are many cases when re-rendering the entire image (overnight or even longer) is just not necessary.

[manitwo]

+1 dusan.

[CTZn]

+1, as usual. I always do a lot of testing before final render, who doesn't ? Best workaround I found so far was to set the display time to 1. As you want a rapid feedback, refreshing cycles are negligible, cpu wise, in this case.

Note that rendering region was already requested in various threads here