With the recent release of Cinema 4D R13, there was one feature that I highly anticipated. That was the ability to write multiple channels into a single EXR frame. Why so important? Well, when you work with 4000+ frames for a sequence and use about 10 passes, that equates to 40,000 frames. Enjoy moving them from drive to drive or re-loading re-rendered assets. Instead, how about we work with just 1 file that contains all the different passes, such as ambient, diffusion, object buffers, etc.

So how do make an OpenEXR file that puts all the channels into one file? Great question! The answer wasn’t as easy as I thought it would be. As my workflow is always going to After Effects to composite the passes together, this is what my output dialog looked like:

As you can see the Multi-Layer file option is grayed out and not available. What gives? Well, it’s an easy enough of an answer, you need to turn off the Save Compositing Project file option if it’s turned on. If it is on, as mine always is, it won’t let you select the Multi-Layer File option. After disabling “Save” on Compositing Project File Section, you can see that you can now make a single OpenEXR with all your render passes:

You’ll just have to save the Compositing Project File 3D data separately. If you need further information about working with OpenEXR and After Effects, visit this article from Adobe. Happy rendering.

Update 2012.26.01

It was asked on twitter by Grischa Theissen @grischatheissen (who you should follow) what the best format to use for OpenEXR. Tim Clapham @hellolux (follow him too, as well as take classes onfxphd.com from him) responded that B44 is built for realtime playback according to official exr docs, and that he uses 16bit float for smaller files unless he really needs 32bit precision.