Pausing rendering process of a single pic?

I was wondering if there is a way to interrupt the rendering process of one single picture and continue later.
Lets say you render a high res pic with lots of soft area lights (sample 16) and ray traced reflections that renders for about one night and half a day. It would be very usefull to be able to interrupt the rendering when you need to do some work on your computer. Whenever you stop working blender continues rendering. Thus only the processors “spare time” is used for rendering. Is this possible?

The only way I can imagine for now is just to hit ESC-key, save the half rendered pic of the backbuffer as a file and start a new rendering later by setting a render border (shift B-key) around the other half of the cam-view. The two halfs of the pic can later be “glued” in Photoshop or something.
But I am not sure if I can safe the backbuffer as a complete file with alpha and everything (when being rendered with RGBA). Does anyone know how to do that?


sounds like an ugly hack, what you describe here ;). no, currently it’s not possible to pause a rendering. sure you figured that out. but did you try what you suggested? it might work. and if not… make a feature request on


You could just lower the priority of the process to the lowest possible on *nix or NT core Windows (2K, XP).


Not of great relevance when using Blender’s internal renderer, but if you export to Pov-Ray, you are able to continue a stopped render (+c command-line switch) at a later date.