filmic tonemapping problem

[ccanan]

according to hable's presentation on uncharted2's hdr lighting.
the filmic tone mapping's function can be found here:
http://filmicgames.com/archives/75

but when I used it in code, I found its curve pretty similar to x/(1+x) style:
(in this case, u know, the contrast drop quickly with brightness grows.)
instead of "s" shape as hable mentioned.

and I tweak the parameter for a while, still failed to get a nice "s" shape curve.
anyone works it out correctly?

actually I used sin function to simulate "s" shape curve, it looks fine, nice contrast, nice smooth highlight part.

thx

 

[Humus]

I believe the s-shape only occurs in log-space, in case you're plotting it in linear space.

We used filmic tonemapping for a while, and the general conclusion was that artists could never figure out what the parameters meant. It's not exactly obvious to me either. It was tweaked by artists several times, with various amount of insane input->output mapping as a result. Then artists complained they couldn't get coloring and lighting right, so I had to add a no-tonemapping option for reference. Ultimately I set out to "tweak it right" and came up with parameters that I was happy with that gave reasonably linear response in the mid-range and had a nice toe and shoulder, and all was well. Then I gave my old favorite a shot, the simple photographic tonemapping operator (ldr = 1 - exp2(-exposure * hdr)). Turns out that gave almost identical results as my tweaked filmic tonemapping. So we dumped filmic in favor of the simpler photographic operator which is intuitive and easy to control and gives good results overall and also is cheaper.

 

[MJP]

I have an demo on my blog that has a bunch of tone mapping operators implemented, and plots the curve on a log scale in real-time so that you can see the results of your tweaking.

 

[Laa-Yosh]

Filmic tone mapping will require filmic lighting which usually means seriously overbright stuff before the tone mapping is applied. Ever been to a TV or movie set and looked into those lights?

The entire (artistic) point of physically correct lighting and shaders and tone mapping is that you can then simply hire a lighter and a director of photography and see them apply their existing real-life skills to your CG scene. Less variables to tweak, less cheating, more predictable results for real-life conditions.

At least that's been our experience when we applied those principles to our offline CG stuff.

 

[ccanan]

Hi, thx , I did check the curve in linear space, that should be the reason I didn't get the curve.