The idea is to make it possible to report extra meta data from
render engine to the file writing. This way we can provide
additional information such as number of samples rendered by
resumable Cycles rendering so we can easily combine files back.
Currently only report number of samples from Cycles when rendering
a single render-layer scene. This is something what was required
here at the studio. We can easily extend that further.
Ideally we would also need to support non-string metadata, but
that's for later.
Reviewers: mont29, campbellbarton
Reviewed By: mont29, campbellbarton
Subscribers: sybren, candreacchio
Differential Revision: https://developer.blender.org/D2502
5296c2e099