functionality

code/game/atoms_movable.dm

@@ -39,6 +39,37 @@
 
 	var/zfalling = FALSE
 
+	/// Either FALSE, [EMISSIVE_BLOCK_GENERIC], or [EMISSIVE_BLOCK_UNIQUE]
+	var/blocks_emissive = FALSE
+	///Internal holder for emissive blocker object, do not use directly use blocks_emissive
+	var/atom/movable/emissive_blocker/em_block
+
+
+/atom/movable/Initialize(mapload)
+	. = ..()
+	switch(blocks_emissive)
+		if(EMISSIVE_BLOCK_GENERIC)
+			update_emissive_block()
+		if(EMISSIVE_BLOCK_UNIQUE)
+			render_target = ref(src)
+			em_block = new(src, render_target)
+			vis_contents += em_block
+
+/atom/movable/Destroy()
+	QDEL_NULL(em_block)
+	return ..()
+
+/atom/movable/proc/update_emissive_block()
+	if(blocks_emissive != EMISSIVE_BLOCK_GENERIC)
+		return
+	if(length(managed_vis_overlays))
+		for(var/a in managed_vis_overlays)
+			var/obj/effect/overlay/vis/vs
+			if(vs.plane == EMISSIVE_BLOCKER_PLANE)
+				SSvis_overlays.remove_vis_overlay(src, list(vs))
+				break
+	SSvis_overlays.add_vis_overlay(src, icon, icon_state, EMISSIVE_BLOCKER_LAYER, EMISSIVE_BLOCKER_PLANE)
+
 /atom/movable/proc/can_zFall(turf/source, levels = 1, turf/target, direction)
 	if(!direction)
 		direction = DOWN

code/game/objects/items.dm

@@ -7,6 +7,7 @@ GLOBAL_VAR_INIT(rpg_loot_items, FALSE)
 /obj/item
 	name = "item"
 	icon = 'icons/obj/items_and_weapons.dmi'
+	blocks_emissive = EMISSIVE_BLOCK_GENERIC
 	var/item_state = null
 	var/lefthand_file = 'icons/mob/inhands/items_lefthand.dmi'
 	var/righthand_file = 'icons/mob/inhands/items_righthand.dmi'