We have now established sky color gradients, and the scenario has a basic sun color.
But if we want to move towards actual dynamic lighting, the Sun/Moon vector must be calculated. This is not just for terrain or planes – also for contrails, particles, glare, etc.
framework/Chronology.cpp contains a sunToHorizon() function, and I added moonToHorizon() to TFXplorer.cpp in 2016 but I never completed it. I now should.