HDR Tonemap Modified Reinhard equation possibly wrong

[jjspace]

I think the current equation for our Modified Reinhard tonemap is slightly wrong

cesium/packages/engine/Source/Shaders/PostProcessStages/ModifiedReinhardTonemapping.glsl

Line 21 in 349364c

color = (color * (1.0 + color / white)) / (1.0 + color);

The original source link seems to no longer exist but judging by these other articles I found the color / white should be color / (white * white)

• https://expf.wordpress.com/2010/05/04/reinhards_tone_mapping_operator/
• https://bruop.github.io/tonemapping/
• https://www.shadertoy.com/view/WdjSW3

This hasn't been touched since the initial HDR PR (#7017) so I don't know the context here that might dictate this as intentional.

This came up during #12160