Colorimetric LUTs

by Tynach

I was unhappy with the default night LUTs, including the night vision LUT. So I made my own, trying to keep it as similar to the original's intent as possible while using color space conversion math to be as accurate to life as possible. All LUTs which change the white balance use chromatic adaptation to shift the colors toward a different white point. I choose white points from the CIE's 'Illuminant series D', also known as the 'daylight locus', which is meant to represent natural daylight at different color temperatures. Luminosity is scaled roughly identically to the default LUTs. All color operations were performed in a linear light scale, then converted back into sRGB for the LUTs themselves. The main LUTs modified are the nighttime ones, though I also added LUTs for night vision equipment and dawn/sunset (the latter which is now actually used by the game). LUT details: * lut-night.png - Color temperature: 25000K; darkest it gets. * lut-riseset.png - Color temperature: 4000K; dawn and sunset, not quite so dark. * night.png - Same as lut-night, but a tiny bit brighter for the map view. * nightvision.png - Simulates a lowered gamut display, and is only very slightly dimmer than standard full daylight ('identity' LUT).

Tweaks
3 years ago
0.18
16

i Demand for LUTs the same lightness as the vanilla ones (use a 2.2 gamma instead of sRGB)?

3 years ago
(updated 3 years ago)

It seems the original Factorio night LUTs were gamma corrected at a gamma of 2.2, rather than following sRGB. This, while teeechnically incorrect, has some benefits:

  • Most LCD displays should use sRGB, but often just use a power of 2.2 gamma function. For such displays, a gamma 2.2 corrected LUT would be more accurate.
  • The darkest areas (that aren't completely black) would become a bit lighter, and this makes a larger difference in LUTs that transform all colors to be darker to begin with, which is the case here.
  • Even with perfectly calibrated sRGB displays, the above improves visibility. Sliiightly washes out the color and removes some of the contrast, but the color differences are still stronger than the vanilla LUT since the chromatic adaptation is performed in LMS space.

Right now, my display is calibrated to the sRGB standard... And the current LUTs look great. But when I look at them without my display calibrations applied, things.. Are nice and contrasty I guess, but I think a little too dark, and definitely darker than I enjoy.

However, since I do play with calibrated monitors most of the time, I'm thinking of trying to make it an option in the mod itself. One of those options that you restart the game to apply (since it changes the LUT filename constants). I don't exactly know how to do that yet, but it looks like there are dedicated modding APIs for it. Maybe have the different sets of LUTs in different folders and have it change which folder it is based on the setting.

But if I'm going to be adding settings, that brings up the possibility of more complicated options - like maybe disabling the sun(rise|set) LUT so it behaves like the normal game and transitions directly from daylight to night.

I suppose that's a separate conundrum, though. Right now, I just want some opinions on if the current LUTs are maybe too dark and/or contrasty for you guys. So, here's a few screenshots that show what the game would look like with these proposed LUTs:

  1. With the same white point as my current LUTs (Standard Illuminant D series at 25000K color temperature):
    https://i.imgur.com/5Z4lujW.png

  2. With the same white point as Factorio's default night LUT (to more fairly show the benefit of proper chromatic adaptation):
    https://i.imgur.com/3o2Bt26.png

3 years ago

please keep it up, love the mod ^_^
and more options are always welcome

3 years ago

Just looking at these 2 pics on an ancient and definitely non-calibrated monitor (my good NEC PA241W died recently), I only see a slight blue-ish tint in the 2nd screenshot (the one with Factorio white point). No perceived difference in brightness in dark areas.

Also, as of current (0.1.0) version of the mod, it seems the night in actual game is somewhat darker than both of the screenshots above. But still manageable, for me at least.

Also also, I absolutely love the sunrise/sunset LUT! Thanks for the great and, as it seems, unique mod!

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