from provided node
"* minor redundant gl call in DrawCone2 optimized away (twice per frame)
* corrected the glRotatef() order in drawRain even further (a less
obvious mistake than before, which is noticed by looking skywards and wiggling
the mouse in the view direction change mode)
* all the "magic numbers" used in the rain rendering code have been
provided a default (based on the old hardcoded value) in a form of a
define, and a meaningfully named static member in SGEnviro"
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