User parameters don't work well

[Summer60]

Thanks a lot for great code! it works pretty well in case of passing direct parameter to it (x0,y0,x1,y1). However, I had no luck in getting a reasonable curve particularly in shoulder area when I used the user parameters. The result shoulder is almost linear. I am not sure if adding y1_offset to x0 is a right thing to do (or maybe it's a typo in line 239). Anyways, what I get is very different from what is shown in the blog post. I implemented the code as it is with the parameters given in the blog. Can you please give me a hint if I am missing something? Thanks for any clarification.

[Summer60]

Can you please address this issue?

[bensyverson]

Hi @Summer60, I ran into the same problem. I believe there's a bug in line 243 of FilmicToneCurve.cpp. The parameter shoulderLength should be used to define the latitude/ceiling in F-stops, but instead, shoulderStrength is being passed in:

fw-public/FilmicCurve/FilmicToneCurve.cpp

Line 243 in 37de36e

float extraW = exp2f(shoulderStrength)-1.0f;

I'm not directly using this repository, but I used it as reference in creating a separate Swift implementation. I made the swap on that line in my repo, and now the User Params work as expected.