gzdoom/wadsrc/static/actors/shared/skies.txt

ACTOR SkyViewpoint native 
{
	+NOSECTOR
	+NOBLOCKMAP
	+NOGRAVITY
	+DONTSPLASH
}

ACTOR SkyPicker native 
{
	+NOSECTOR
	+NOBLOCKMAP
	+NOGRAVITY
	+DONTSPLASH
}

Actor SkyCamCompat : SkyViewpoint native
{
}

ACTOR StackPoint : SkyViewpoint native 
{
}

ACTOR UpperStackLookOnly : StackPoint
{
}

ACTOR LowerStackLookOnly : StackPoint
{
}


ACTOR SectorSilencer native 
{
	+NOBLOCKMAP
	+NOGRAVITY
	+DONTSPLASH
	RenderStyle None
}