what would be nice, is if there was a way to select only a part of what the camera sees (lets say upper left quadrant) if it was the only part of the scene with animation. this way, when producing animations relying on small size you could just layer the animated quadrant over the nonanimated background.
Shift-B-Key in the camera view, then draw your box. The “Border” button under the “Render” tab turns it back off.
For more discussion on using the backbuf for running an animation of just a portion of the screen and overlaying, see this thread:
wow.
i’m amazed everytime i ask a question that there is an answer.
extra credit for the blender design team.
edit:although, it still renders the whole image 
maybe something else to push as well?
mzungu has it right…
shift+B, mark the square and hit F12…
The marked area renders in the render window…
steen
yup.
that’s exactly what i did.
but it’s still rendering the whole view of the camera.
i’m using the new 2.40
maybe it’s not working until the full release?
dunno about 2.40…
if you have the “crop” button pressed (under the “format” tab, next to the output file format dropdown) it may be just displaying the area within the border - otherwise, don’t know what you’re getting without some screen captures to show us…
Works here in 2.4. Make sure that “Border” button is pressed in F10, Render tab (should happen automatically when you use Shft-B.
%<
the render is the exact same as always.
big. shouldn’t this only render the little box in red?
i’ve done it exactly how everyone says, but it isn’t working.
maybe i need to reinstall.
oh, it only works for blender internal rending.
not yafray.
that sucks.