qzdoom/wadsrc/static/actors/hexen/fog.txt

// Fog Spawner --------------------------------------------------------------

ACTOR FogSpawner
{
	+NOSECTOR +NOBLOCKMAP
	+FLOATBOB
	+NOGRAVITY
	+INVISIBLE

	action native A_FogSpawn();

	States
	{
	Spawn:
		TNT1 A 20 A_FogSpawn
		Loop
	}
}

// Small Fog Patch ----------------------------------------------------------

ACTOR FogPatchSmall
{
	Speed 1
	+NOBLOCKMAP +NOGRAVITY +NOCLIP +FLOAT
	+NOTELEPORT
	RenderStyle Translucent
	Alpha 0.6

	action native A_FogMove();

	States
	{
	Spawn:
		FOGS ABCDE 7 A_FogMove
		Loop
	Death:
		FOGS E 5
		Stop
	}
}

// Medium Fog Patch ---------------------------------------------------------

ACTOR FogPatchMedium : FogPatchSmall
{
	States
	{
	Spawn:
		FOGM ABCDE 7 A_FogMove
		Loop
	Death:
		FOGS ABCDE 5
		Goto Super::Death
	}
}

// Large Fog Patch ----------------------------------------------------------

ACTOR FogPatchLarge : FogPatchMedium
{
	States
	{
	Spawn:
		FOGL ABCDE 7 A_FogMove
		Loop
	Death:
		FOGM ABCDEF 4
		Goto Super::Death
	}
}