Disable q3map2 backsplash by default (in the -light stage)
The q3map2 backsplash feature was added recently (imported from NRC):
-backsplash <Fscale Fdistance> scale area lights backsplash fraction + set
distance globally; (distance < -900 to omit
distance setting); default = 1 23; real area lights
have no backsplash (scale = 0); q3map_backsplash
shader keyword overrides this setting
However it causes issues on some maps, see netradiant#189
To avoid regressions, it's probably safer to disable it by default, and if we want to enable it for a specific map, we can still edit *.map.options
.