4.19 Physical Lights

[Kel_Solaar]

@Kel_Solaar

For future reference, we spent a few hours digging and found out where the 1.2 value is coming from: It is actually normative as per ISO12232:2006, i.e. an ISO Standard derived value, referenced in Wikipedia, in Moving Frostbite to Physically Based Rendering 3.0 (and confirmed by that bit of maths in Unity code):

 

  1. // Compute the maximum luminance possible with H_sbs sensitivity
  1. // maxLum = 78 / ( S * q ) * N^2 / t
  1. // = 78 / ( S * q ) * 2^ EV_100
  1. // = 78 / (100 * 0.65) * 2^ EV_100
  1. // = 1.2 * 2^ EV
  1. // Reference: http://en.wikipedia.org/wiki/Film_speed

 

Cheers,

Thomas

So Epic has just documented that whole thing properly which is great: How Epic Games is handling auto exposure in 4.25 - Unreal Engine

Thanks!