So far, I’m pretty much replicating the curves which are used by filmic anyways, so the results will be the same. This is (so far) mostly an exercise in coming up with ways to control those curves to make them easier to handle. I think so far, that can be done well enough just on curves.
Using different functions for the roll-off, on the other hand, is likely to make visible differences, particularly once you push the parameters out of the range where the current curve looks fine anyway.
But then, if I’m going to apply any curve type I come up wih to an image, I think the best way to do that would be within Darktable because otherwise there’s still a bunch of things I’d need to get right to make sure my conclusions can be transferred. (“Yeah sure looks nice, but you didn’t take into account that DT actually applies before handing the image to filmic”. “cool but that’s already part of the colour management pipeline”. "that won’t fly in DT because it needs to be able to do ". Or, my favourite: “You can get the same effect by using this 27-step procedure, so we’re not going to allow that stuff in DT anyway”).
So … yes, I’d like to know what people think before I put serious time in. I’d also be happy if someone could lend me a hand in setting up a routine for me to fork DT, change some code and compile it, and point me to where in the code the filmic curve lives.
Alternative: Is there a way to export the exact image data that is fed to filmic in DT, and to insert whatever I produce in Python from it back into DT at the correct point in the pipeline? Or a how-to? I keep stumbling over information and discussions I wasn’t aware of, so I think it is smarter to ask first than to reinvent the wheel and look stupid later.