Consider this rfactors lighting system work via a geo location system as since rf1. Hdr is dependant of the track and suns location at a certain longitude and latitude position in time and season, if we eliminate weather from the equation it should remain consistant along the equator where as further north or south the horizon and skyline may come into play. We can then start to add weather effects, cloud coverage etc. Dawn till dusk colouring and start to see changes in colour of light and intensity. Other effects are all driven from these basic set standards. A track modeller will depend on these variables for accurately modeling colour at a particular time of day, yes hdr is an overlay but it has the same importance as lighting as they are the same thing. Hdr and lighting are both tweaked together not one after another, then tweaked again once you add the weather variable, then with all three will the overlayed eye effects or camera effects be added. Atleast in a logical sence that is the path most programmers and designers should take.