This way it is possible to define render border directly from the image editor,
which is useful for at least three things:
- If viewport is really optimized out (simplified etc) then it might be hard to
guess which exact area you're mainly interested now.
- No need to switch to the viewport to do render border tweaks, could be useful
when doing compositing.
- If one need to look at particular pixel(s) which is real handy for debugging
render engines (both Cycles and BI).
Reviewers: campbellbarton, venomgfx
Reviewed By: venomgfx
Differential Revision: https://developer.blender.org/D820
0ba84b7124