From Valve Developer Community
constdirectionallightdot is used to calculate light intensity rather than the normal directional dot product. Only valid if
$staticprop) is also set.
Tip:This command is useful for foliage models.
$modelname props_foliage\hedge_256_128high.mdl $body "Body" "hedge_256_128high_reference.smd" $staticprop $constantdirectionallight 0.15 $surfaceprop "wood_solid"