Tonemapping: Added Luma-based Reinhard Tonemapping Option #3
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Description
I propose the addition of Reinhard-Luminance tonemapping, from this blog post. On that page, this is the function
reinhard_extended_luminancewithmax_white_lset to infinity, and then the equation simplified. According to these sources (1 2 3), the correct luminance coefficients for linear light are (0.2126, 0.7152, 0.0722), which is also the coefficients given in that blog post. The coefficients (0.299, 0.587, 0.114) which are pervasive in three.js are incorrect, but work better when the input is in sRGB/gamma space.This is a trivial improvement to the existing Reinhard tonemapping. The difference is that Reinhard-Luminance uses lumninance in the denominator, rather than curving the color channels independently. Curving the color channels independently can result in desaturation and incorrect hue (the hue veers towards cyan, yellow, or magenta). Reinhard-Luminance does the best job of not doing that.
The existing tonemapping options quickly become saturated at sizeable exposure values. At low exposure values, Cineon and ACES are underexposed. Reinhard-Luminance doesn't have these issues.
From my testing, some of the tonemapping options look good at certain brightnesses, but only Reinhard-Luminance looks consistently good at all brightnesses.
This contribution is funded by Threekit