(Note up front: Should we move this discussion to the OIDN thread in the dev forum? Might be better suited there.)
I got the testscenes working now (with the commandline tool in the end).
For the implementation, we should discuss/decide some points:
1) As the purpose is to make large scenes fit into ram to avoid swap-speed-penalties, it would technically be ideal to have a check for available memory, then decide if to do split or single OIDN pass. I don't know how well this can be done, and also I don't think I could implement it (let alone cross platform), but I could prepare for it. Otherwise, hardcode it so that it is always split for >= 8Mpix (i.e. 4K)?
2) Input parameters: number of slices: technically should also be dependent on RAM + image size. Although we can choose a hardcoded value like 8, which should cover most reasonable combinations that people will use. If someone really wants to run OIDN on a 200Mpix render, well...
3) Input parameters: number of pixels overlap: can probably be hardcoded, my tests yesterday used only 50 pixels. Any objections why it should be variable?
4)B.Y.O.B., you said something about not needing buffers if you do horizontal stripes. I might understand what you mean when I look further into the current implementation, but could you elaborate for me anyways?