Applying animated compositor to pre-rendered animation frames

Question

I'm trying to figure out a good workflow for setting up the compositor for animations.

When I make still images, I render at high-quality first, then touch things up with the compositor. With this workflow, the time-hungry stuff (i.e. the rendering) happens at the beginning, then I tweak the dials in the compositor at the end until it looks good.

For animations, it seems that the compositor should be set up and finalized at render-time, when the series of stills are saved out.

I'd like to adapt my still-image workflow to developing animations. I can imagine saving out the raw animation renders first (takes a long time), then filter all of the frames through the composite nodes at the end (relatively quick).

The compositing and the rendering should probably happen in the same .blend file, because it would nice to use the animation drivers for compositing values.

Is there a nice way to achieve this?

Answer 1

There doesn't need to be a big change, the compositor can read a sequence of images just as easily as a single image.

I would recommend saving your render files as openexr multilayer. The files are larger but they can include all render layers and output sockets that you normally use in the compositor. If you specify a full filename remember to add some #'s to get a frame number included.

After saving your animation frames, create a new scene and in the compositor start with an Input->Image node and open all of your images. This leaves you with one scene to do the heavy rendering and one for only compositing and it's all in the one blend file. As the same nodes will apply to the entire sequence you may want to create several scenes for compositing to get different effects in different shots of your animation.