Add 3 new setting values, increasing the distance at which a lower level of detail is used by factors of 1.6, 2.0 and 3.0 (default is 1.25). This allows players for which getting enough FPS is not an issue to reduce pop-in and improve the looks of tracks.
In local testing with a strong CPU and a weak GPU, the performance impact of increasing the view distances is small and well worth it, but this may vary from system to system. More testing is needed on different systems, but this suggests room to increase minimum, default and maximum values in future releases.
This patch also slightly changes the auto-computation of LoD distance, making the transition around a distance of 250 smoother.
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