Icon smooth refactor (#52864)

bitflag list construct added: an associative list of bitflags for cheap and quick element comparison between two lists using the same system.

    canSmoothWith list turned into a bitflag list.

    smoothing_groups list added to substitute the type path list.

    smoothing procs turned into atom procs, refactored and optimized a bit.

    smooth directions redefined in order to fit in 8 bits for a future smoothing system

    some variable names changed, foreseeing a second smoothing system

    SMOOTH_OBJ flag added, for things that need to scan turfs for smoothing. The old locate() optimization has the risk of returning false negatives by finding a child and returning null while there might be one of the wanted type as well, as it doesn't match the type exactly.

    SMOOTH_TRUE and SMOOTH_MORE condensed into SMOOTH_CORNERS. The old behavior can be replicated using smoothing groups without loss.

    Does very minor code cleanup.

    Processing-wise didn't find a noticeable difference. The system loses on init a bit by setting the bitflag_lists, and by scanning whole turf contents for object smoothing (increasing accuracy), and gains by making less checks per target to smooth, through the same bitflag_lists.

    Memory-wise there should be a small improvement, given that on the old system we had 63512 canSmoothWith lists (a few typelists, most unique), and on this new system canSmoothWith + smoothing_groups are both bitflag_lists from the same pool, totaling 46 in number.

Could be tested a bit to see if I missed any icons not properly smoothing.

code/__DEFINES/icon_smoothing.dm

@@ -0,0 +1,101 @@
+/* smoothing_flags */
+#define SMOOTH_CORNERS	(1<<0) //Smoothing system in where adjacencies are calculated and used to build an image by mounting each corner at runtime.
+#define SMOOTH_DIAGONAL	(1<<2)	//if atom should smooth diagonally, this should be present in 'smoothing_flags' var
+#define SMOOTH_BORDER	(1<<3)	//atom will smooth with the borders of the map
+#define SMOOTH_QUEUED	(1<<4)	//atom is currently queued to smooth.
+#define SMOOTH_OBJ		(1<<5)	//smooths with objects, and will thus need to scan turfs for contents.
+
+
+/*smoothing macros*/
+
+#define QUEUE_SMOOTH(thing_to_queue) if(thing_to_queue.smoothing_flags) {SSicon_smooth.add_to_queue(thing_to_queue)}
+
+#define QUEUE_SMOOTH_NEIGHBORS(thing_to_queue) for(var/neighbor in orange(1, thing_to_queue)) {var/atom/atom_neighbor = neighbor; QUEUE_SMOOTH(atom_neighbor)}
+
+
+/**SMOOTHING GROUPS
+ * Groups of things to smooth with.
+ * * Contained in the `list/smoothing_groups` variable.
+ * * Matched with the `list/canSmoothWith` variable to check whether smoothing is possible or not.
+ */
+
+#define S_TURF(num) ((24 * 0) + num) //Not any different from the number itself, but kept this way in case someone wants to expand it by adding stuff before it.
+/* /turf only */
+
+#define SMOOTH_GROUP_TURF_OPEN S_TURF(0)				///turf/open
+#define SMOOTH_GROUP_TURF_CHASM S_TURF(1)				///turf/open/chasm, /turf/open/floor/fakepit
+#define SMOOTH_GROUP_FLOOR_LAVA S_TURF(2)				///turf/open/lava/smooth
+#define SMOOTH_GROUP_FLOOR_TRANSPARENT_GLASS S_TURF(3)	///turf/open/transparent/glass
+
+#define SMOOTH_GROUP_OPEN_FLOOR S_TURF(4)				///turf/open/floor
+
+#define SMOOTH_GROUP_FLOOR_ASH S_TURF(5)				///turf/open/floor/plating/ashplanet/ash
+#define SMOOTH_GROUP_FLOOR_ASH_ROCKY S_TURF(6)			///turf/open/floor/plating/ashplanet/rocky
+#define SMOOTH_GROUP_FLOOR_ICE S_TURF(7)				///turf/open/floor/plating/ice
+#define SMOOTH_GROUP_FLOOR_SNOWED S_TURF(8)				///turf/open/floor/plating/snowed
+
+#define SMOOTH_GROUP_CARPET S_TURF(10)					///turf/open/floor/carpet
+#define SMOOTH_GROUP_CARPET_BLACK S_TURF(11)			///turf/open/floor/carpet/black
+#define SMOOTH_GROUP_CARPET_BLUE S_TURF(12)				///turf/open/floor/carpet/blue
+#define SMOOTH_GROUP_CARPET_CYAN S_TURF(13)				///turf/open/floor/carpet/cyan
+#define SMOOTH_GROUP_CARPET_GREEN S_TURF(14)			///turf/open/floor/carpet/green
+#define SMOOTH_GROUP_CARPET_ORANGE S_TURF(15)			///turf/open/floor/carpet/orange
+#define SMOOTH_GROUP_CARPET_PURPLE S_TURF(16)			///turf/open/floor/carpet/purple
+#define SMOOTH_GROUP_CARPET_RED	S_TURF(17)				///turf/open/floor/carpet/red
+#define SMOOTH_GROUP_CARPET_ROYAL_BLACK S_TURF(18)		///turf/open/floor/carpet/royalblack
+#define SMOOTH_GROUP_CARPET_ROYAL_BLUE S_TURF(19)		///turf/open/floor/carpet/royalblue
+
+#define SMOOTH_GROUP_CLOSED_TURFS S_TURF(24)			///turf/closed
+#define SMOOTH_GROUP_MATERIAL_WALLS S_TURF(25)			///turf/closed/wall/material
+#define SMOOTH_GROUP_SYNDICATE_WALLS S_TURF(26)			///turf/closed/wall/r_wall/syndicate
+#define SMOOTH_GROUP_HOTEL_WALLS S_TURF(27)				///turf/closed/indestructible/hotelwall
+#define SMOOTH_GROUP_MINERAL_WALLS S_TURF(28)			///turf/closed/mineral, /turf/closed/indestructible
+#define SMOOTH_GROUP_BOSS_WALLS S_TURF(29)				///turf/closed/indestructible/riveted/boss
+#define SMOOTH_GROUP_SURVIVAL_TITANIUM_WALLS S_TURF(30)	///turf/closed/wall/mineral/titanium/survival
+
+#define MAX_S_TURF SMOOTH_GROUP_SURVIVAL_TITANIUM_WALLS //Always match this value with the one above it.
+
+
+#define S_OBJ(num) (MAX_S_TURF + 1 + num)
+/* /obj included */
+
+#define SMOOTH_GROUP_WALLS S_OBJ(0)						///turf/closed/wall, /obj/structure/falsewall
+#define SMOOTH_GROUP_URANIUM_WALLS S_OBJ(1)				///turf/closed/wall/mineral/uranium, /obj/structure/falsewall/uranium
+#define SMOOTH_GROUP_GOLD_WALLS S_OBJ(2)				///turf/closed/wall/mineral/gold, /obj/structure/falsewall/gold
+#define SMOOTH_GROUP_SILVER_WALLS S_OBJ(3)				///turf/closed/wall/mineral/silver, /obj/structure/falsewall/silver
+#define SMOOTH_GROUP_DIAMOND_WALLS S_OBJ(4)				///turf/closed/wall/mineral/diamond, /obj/structure/falsewall/diamond
+#define SMOOTH_GROUP_PLASMA_WALLS S_OBJ(5)				///turf/closed/wall/mineral/plasma, /obj/structure/falsewall/plasma
+#define SMOOTH_GROUP_BANANIUM_WALLS S_OBJ(6)			///turf/closed/wall/mineral/bananium, /obj/structure/falsewall/bananium
+#define SMOOTH_GROUP_SANDSTONE_WALLS S_OBJ(7)			///turf/closed/wall/mineral/sandstone, /obj/structure/falsewall/sandstone
+#define SMOOTH_GROUP_WOOD_WALLS S_OBJ(8)				///turf/closed/wall/mineral/wood, /obj/structure/falsewall/wood
+#define SMOOTH_GROUP_IRON_WALLS S_OBJ(9)				///turf/closed/wall/mineral/iron, /obj/structure/falsewall/iron
+#define SMOOTH_GROUP_ABDUCTOR_WALLS S_OBJ(10)			///turf/closed/wall/mineral/abductor, /obj/structure/falsewall/abductor
+#define SMOOTH_GROUP_TITANIUM_WALLS S_OBJ(11)			///turf/closed/wall/mineral/titanium, /obj/structure/falsewall/titanium
+#define SMOOTH_GROUP_PLASTITANIUM_WALLS S_OBJ(13)		///turf/closed/wall/mineral/plastitanium, /obj/structure/falsewall/plastitanium
+#define SMOOTH_GROUP_SURVIVAL_TIANIUM_POD S_OBJ(14)		///turf/closed/wall/mineral/titanium/survival/pod, /obj/machinery/door/airlock/survival_pod, /obj/structure/window/shuttle/survival_pod
+
+#define SMOOTH_GROUP_PAPERFRAME S_OBJ(20)				///obj/structure/window/paperframe, /obj/structure/mineral_door/paperframe
+
+#define SMOOTH_GROUP_WINDOW_FULLTILE S_OBJ(21)			///obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile
+
+#define SMOOTH_GROUP_LATTICE  S_OBJ(30)					///obj/structure/lattice
+
+#define SMOOTH_GROUP_AIRLOCK S_OBJ(40)					///obj/machinery/door/airlock
+
+#define SMOOTH_GROUP_TABLES S_OBJ(50)					///obj/structure/table
+#define SMOOTH_GROUP_WOOD_TABLES S_OBJ(51)				///obj/structure/table/wood
+#define SMOOTH_GROUP_FANCY_WOOD_TABLES S_OBJ(52)		///obj/structure/table/wood/fancy
+#define SMOOTH_GROUP_BRONZE_TABLES S_OBJ(53)			///obj/structure/table/bronze
+
+#define SMOOTH_GROUP_ALIEN_RESIN S_OBJ(60)				///obj/structure/alien/resin
+#define SMOOTH_GROUP_ALIEN_WALLS S_OBJ(61)				///obj/structure/alien/resin/wall, /obj/structure/alien/resin/membrane
+#define SMOOTH_GROUP_ALIEN_WEEDS S_OBJ(62)				///obj/structure/alien/weeds
+
+#define SMOOTH_GROUP_SECURITY_BARRICADE S_OBJ(63)		///obj/structure/barricade/security
+#define SMOOTH_GROUP_SANDBAGS S_OBJ(64)					///obj/structure/barricade/sandbags
+
+#define SMOOTH_GROUP_HEDGE_FLUFF S_OBJ(65)				///obj/structure/fluff/hedge
+
+#define SMOOTH_GROUP_SHUTTLE_PARTS S_OBJ(66)			///obj/structure/window/shuttle, /obj/structure/shuttle/engine/heater
+
+#define SMOOTH_GROUP_CLEANABLE_DIRT	S_OBJ(67)			///obj/effect/decal/cleanable/dirt

code/__HELPERS/bitflag_lists.dm

@@ -0,0 +1,25 @@
+GLOBAL_LIST_EMPTY(bitflag_lists)
+
+/**
+  * System for storing bitflags past the 24 limit, making use of an associative list.
+  *
+  * Macro converts a list of integers into an associative list of bitflag entries for quicker comparison.
+  * Example: list(0, 4, 26, 32)) => list( "0" = ( (1<<0) | (1<<4) ), "1" = ( (1<<2) | (1<<8) ) )
+  * Lists are cached into a global list of lists to avoid identical duplicates.
+  * This system makes value comparisons faster than pairing every element of one list with every element of the other for evaluation.
+  *
+  * Arguments:
+  * * target - List of integers.
+  */
+#define SET_BITFLAG_LIST(target) \
+	do { \
+		var/txt_signature = target.Join("-"); \
+		if(!GLOB.bitflag_lists[txt_signature]) { \
+			var/list/new_bitflag_list = list(); \
+			for(var/value in target) { \
+				new_bitflag_list["[round(value / 24)]"] |= (1 << (value % 24)); \
+			}; \
+			GLOB.bitflag_lists[txt_signature] = new_bitflag_list; \
+		}; \
+		target = GLOB.bitflag_lists[txt_signature]; \
+	} while (FALSE)

code/__HELPERS/icon_smoothing.dm

@@ -4,7 +4,8 @@
 	Each tile is divided in 4 corners, each corner has an appearance associated to it; the tile is then overlayed by these 4 appearances
 	To use this, just set your atom's 'smoothing_flags' var to 1. If your atom can be moved/unanchored, set its 'can_be_unanchored' var to 1.
 	If you don't want your atom's icon to smooth with anything but atoms of the same type, set the list 'canSmoothWith' to null;
-	Otherwise, put all types you want the atom icon to smooth with in 'canSmoothWith' INCLUDING THE TYPE OF THE ATOM ITSELF.
+	Otherwise, put all the smoothing groups you want the atom icon to smooth with in 'canSmoothWith', including the group of the atom itself.
+	Smoothing groups are just shared flags between objects. If one of the 'canSmoothWith' of A matches one of the `smoothing_groups` of B, then A will smooth with B.
 
 	Each atom has its own icon file with all the possible corner states. See 'smooth_wall.dmi' for a template.
 
@@ -24,104 +25,92 @@
 */
 
 //Redefinitions of the diagonal directions so they can be stored in one var without conflicts
-#define N_NORTH		(1<<1)
-#define N_SOUTH		(1<<2)
-#define N_EAST		(1<<4)
-#define N_WEST		(1<<8)
-#define N_NORTHEAST	(1<<5)
-#define N_NORTHWEST	(1<<9)
+#define N_NORTH		NORTH //(1<<0)
+#define N_SOUTH		SOUTH //(1<<1)
+#define N_EAST		EAST  //(1<<2)
+#define N_WEST		WEST  //(1<<3)
+#define N_NORTHEAST	(1<<4)
+#define N_NORTHWEST	(1<<5)
 #define N_SOUTHEAST	(1<<6)
-#define N_SOUTHWEST	(1<<10)
+#define N_SOUTHWEST	(1<<7)
 
-#define SMOOTH_TRUE		(1<<0)	//smooths with exact specified types or just itself
-#define SMOOTH_MORE		(1<<1)	//smooths with all subtypes of specified types or just itself (this value can replace SMOOTH_TRUE)
-#define SMOOTH_DIAGONAL	(1<<2)	//if atom should smooth diagonally, this should be present in 'smoothing_flags' var
-#define SMOOTH_BORDER	(1<<3)	//atom will smooth with the borders of the map
-#define SMOOTH_QUEUED	(1<<4)	//atom is currently queued to smooth.
-
-#define NULLTURF_BORDER 123456789
+#define NO_ADJ_FOUND 0
+#define ADJ_FOUND 1
+#define NULLTURF_BORDER 2
 
 #define DEFAULT_UNDERLAY_ICON 			'icons/turf/floors.dmi'
 #define DEFAULT_UNDERLAY_ICON_STATE 	"plating"
 
 
-#define QUEUE_SMOOTH(thing_to_queue) if(thing_to_queue.smoothing_flags) {SSicon_smooth.add_to_queue(thing_to_queue)}
+///Scans all adjacent turfs to find targets to smooth with.
+/atom/proc/calculate_adjacencies()
+	. = NONE
 
-#define QUEUE_SMOOTH_NEIGHBORS(thing_to_queue) for(var/neighbor in orange(1, thing_to_queue)) {var/atom/atom_neighbor = neighbor; QUEUE_SMOOTH(atom_neighbor)}
-
-
-/proc/calculate_adjacencies(atom/A)
-	if(!A.loc)
-		return 0
-
-	var/adjacencies = 0
-
-	var/atom/movable/AM
-	if(ismovable(A))
-		AM = A
-		if(AM.can_be_unanchored && !AM.anchored)
-			return 0
+	if(!loc)
+		return
 
 	for(var/direction in GLOB.cardinals)
-		AM = find_type_in_direction(A, direction)
-		if(AM == NULLTURF_BORDER)
-			if((A.smoothing_flags & SMOOTH_BORDER))
-				adjacencies |= 1 << direction
-		else if( (AM && !istype(AM)) || (istype(AM) && AM.anchored) )
-			adjacencies |= 1 << direction
+		switch(find_type_in_direction(direction))
+			if(NULLTURF_BORDER)
+				if((smoothing_flags & SMOOTH_BORDER))
+					. |= direction //BYOND and smooth dirs are the same for cardinals
+			if(ADJ_FOUND)
+				. |= direction //BYOND and smooth dirs are the same for cardinals
 
-	if(adjacencies & N_NORTH)
-		if(adjacencies & N_WEST)
-			AM = find_type_in_direction(A, NORTHWEST)
-			if(AM == NULLTURF_BORDER)
-				if((A.smoothing_flags & SMOOTH_BORDER))
-					adjacencies |= N_NORTHWEST
-			else if( (AM && !istype(AM)) || (istype(AM) && AM.anchored) )
-				adjacencies |= N_NORTHWEST
-		if(adjacencies & N_EAST)
-			AM = find_type_in_direction(A, NORTHEAST)
-			if(AM == NULLTURF_BORDER)
-				if((A.smoothing_flags & SMOOTH_BORDER))
-					adjacencies |= N_NORTHEAST
-			else if( (AM && !istype(AM)) || (istype(AM) && AM.anchored) )
-				adjacencies |= N_NORTHEAST
+	if(. & N_NORTH)
+		if(. & N_WEST)
+			switch(find_type_in_direction(NORTHWEST))
+				if(NULLTURF_BORDER)
+					if((smoothing_flags & SMOOTH_BORDER))
+						. |= N_NORTHWEST
+				if(ADJ_FOUND)
+					. |= N_NORTHWEST
 
-	if(adjacencies & N_SOUTH)
-		if(adjacencies & N_WEST)
-			AM = find_type_in_direction(A, SOUTHWEST)
-			if(AM == NULLTURF_BORDER)
-				if((A.smoothing_flags & SMOOTH_BORDER))
-					adjacencies |= N_SOUTHWEST
-			else if( (AM && !istype(AM)) || (istype(AM) && AM.anchored) )
-				adjacencies |= N_SOUTHWEST
-		if(adjacencies & N_EAST)
-			AM = find_type_in_direction(A, SOUTHEAST)
-			if(AM == NULLTURF_BORDER)
-				if((A.smoothing_flags & SMOOTH_BORDER))
-					adjacencies |= N_SOUTHEAST
-			else if( (AM && !istype(AM)) || (istype(AM) && AM.anchored) )
-				adjacencies |= N_SOUTHEAST
+		if(. & N_EAST)
+			switch(find_type_in_direction(NORTHEAST))
+				if(NULLTURF_BORDER)
+					if((smoothing_flags & SMOOTH_BORDER))
+						. |= N_NORTHEAST
+				if(ADJ_FOUND)
+					. |= N_NORTHEAST
+
+	if(. & N_SOUTH)
+		if(. & N_WEST)
+			switch(find_type_in_direction(SOUTHWEST))
+				if(NULLTURF_BORDER)
+					if((smoothing_flags & SMOOTH_BORDER))
+						. |= N_SOUTHWEST
+				if(ADJ_FOUND)
+					. |= N_SOUTHWEST
+
+		if(. & N_EAST)
+			switch(find_type_in_direction(SOUTHEAST))
+				if(NULLTURF_BORDER)
+					if((smoothing_flags & SMOOTH_BORDER))
+						. |= N_SOUTHEAST
+				if(ADJ_FOUND)
+					. |= N_SOUTHEAST
+
+
+/atom/movable/calculate_adjacencies()
+	if(can_be_unanchored && !anchored)
+		return NONE
+	return ..()
 
-	return adjacencies
 
 //do not use, use QUEUE_SMOOTH(atom)
-/proc/smooth_icon(atom/A)
-	if(!A || !A.smoothing_flags)
-		return
-	A.smoothing_flags &= ~SMOOTH_QUEUED
-	if (!A.z)
-		return
-	if(QDELETED(A))
-		return
-	if(A.smoothing_flags & (SMOOTH_TRUE | SMOOTH_MORE))
-		var/adjacencies = calculate_adjacencies(A)
-
-		if(A.smoothing_flags & SMOOTH_DIAGONAL)
-			A.diagonal_smooth(adjacencies)
+/atom/proc/smooth_icon()
+	smoothing_flags &= ~SMOOTH_QUEUED
+	if (!z)
+		CRASH("[type] called smooth_icon() without being on a z-level")
+	if(smoothing_flags & SMOOTH_CORNERS)
+		if(smoothing_flags & SMOOTH_DIAGONAL)
+			corners_diagonal_smooth(calculate_adjacencies())
 		else
-			cardinal_smooth(A, adjacencies)
+			corners_cardinal_smooth(calculate_adjacencies())
 
-/atom/proc/diagonal_smooth(adjacencies)
+
+/atom/proc/corners_diagonal_smooth(adjacencies)
 	switch(adjacencies)
 		if(N_NORTH|N_WEST)
 			replace_smooth_overlays("d-se","d-se-0")
@@ -142,45 +131,50 @@
 			replace_smooth_overlays("d-nw","d-nw-1")
 
 		else
-			cardinal_smooth(src, adjacencies)
-			return
+			corners_cardinal_smooth(adjacencies)
+			return FALSE
 
 	icon_state = ""
-	return adjacencies
+	return TRUE
+
 
 //only walls should have a need to handle underlays
-/turf/closed/wall/diagonal_smooth(adjacencies)
-	adjacencies = reverse_ndir(..())
-	if(adjacencies)
-		var/mutable_appearance/underlay_appearance = mutable_appearance(layer = TURF_LAYER, plane = FLOOR_PLANE)
-		var/list/U = list(underlay_appearance)
-		if(fixed_underlay)
-			if(fixed_underlay["space"])
-				underlay_appearance.icon = 'icons/turf/space.dmi'
-				underlay_appearance.icon_state = SPACE_ICON_STATE
-				underlay_appearance.plane = PLANE_SPACE
-			else
-				underlay_appearance.icon = fixed_underlay["icon"]
-				underlay_appearance.icon_state = fixed_underlay["icon_state"]
+/turf/closed/wall/corners_diagonal_smooth(adjacencies)
+	. = ..()
+	if(!.)
+		return
+	adjacencies = reverse_ndir(adjacencies)
+	if(adjacencies == NONE)
+		return
+	var/mutable_appearance/underlay_appearance = mutable_appearance(layer = TURF_LAYER, plane = FLOOR_PLANE)
+	var/list/U = list(underlay_appearance)
+	if(fixed_underlay)
+		if(fixed_underlay["space"])
+			underlay_appearance.icon = 'icons/turf/space.dmi'
+			underlay_appearance.icon_state = SPACE_ICON_STATE
+			underlay_appearance.plane = PLANE_SPACE
 		else
-			var/turned_adjacency = turn(adjacencies, 180)
-			var/turf/T = get_step(src, turned_adjacency)
-			if(!T.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
-				T = get_step(src, turn(adjacencies, 135))
-				if(!T.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
-					T = get_step(src, turn(adjacencies, 225))
-			//if all else fails, ask our own turf
-			if(!T.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency) && !get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
-				underlay_appearance.icon = DEFAULT_UNDERLAY_ICON
-				underlay_appearance.icon_state = DEFAULT_UNDERLAY_ICON_STATE
-		underlays = U
+			underlay_appearance.icon = fixed_underlay["icon"]
+			underlay_appearance.icon_state = fixed_underlay["icon_state"]
+	else
+		var/turned_adjacency = turn(adjacencies, 180)
+		var/turf/neighbor_turf = get_step(src, turned_adjacency)
+		if(!neighbor_turf.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
+			neighbor_turf = get_step(src, turn(adjacencies, 135))
+			if(!neighbor_turf.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
+				neighbor_turf = get_step(src, turn(adjacencies, 225))
+		//if all else fails, ask our own turf
+		if(!neighbor_turf.get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency) && !get_smooth_underlay_icon(underlay_appearance, src, turned_adjacency))
+			underlay_appearance.icon = DEFAULT_UNDERLAY_ICON
+			underlay_appearance.icon_state = DEFAULT_UNDERLAY_ICON_STATE
+	underlays = U
 
-		// Drop posters which were previously placed on this wall.
-		for(var/obj/structure/sign/poster/P in src)
-			P.roll_and_drop(src)
+	// Drop posters which were previously placed on this wall.
+	for(var/obj/structure/sign/poster/wall_poster in src)
+		wall_poster.roll_and_drop(src)
 
 
-/proc/cardinal_smooth(atom/A, adjacencies)
+/atom/proc/corners_cardinal_smooth(adjacencies)
 	//NW CORNER
 	var/nw = "1-i"
 	if((adjacencies & N_NORTH) && (adjacencies & N_WEST))
@@ -233,64 +227,67 @@
 		else if(adjacencies & N_EAST)
 			se = "4-e"
 
-	var/list/New
+	var/list/new_overlays
 
-	if(A.top_left_corner != nw)
-		A.cut_overlay(A.top_left_corner)
-		A.top_left_corner = nw
-		LAZYADD(New, nw)
+	if(top_left_corner != nw)
+		cut_overlay(top_left_corner)
+		top_left_corner = nw
+		LAZYADD(new_overlays, nw)
 
-	if(A.top_right_corner != ne)
-		A.cut_overlay(A.top_right_corner)
-		A.top_right_corner = ne
-		LAZYADD(New, ne)
+	if(top_right_corner != ne)
+		cut_overlay(top_right_corner)
+		top_right_corner = ne
+		LAZYADD(new_overlays, ne)
 
-	if(A.bottom_right_corner != sw)
-		A.cut_overlay(A.bottom_right_corner)
-		A.bottom_right_corner = sw
-		LAZYADD(New, sw)
+	if(bottom_right_corner != sw)
+		cut_overlay(bottom_right_corner)
+		bottom_right_corner = sw
+		LAZYADD(new_overlays, sw)
 
-	if(A.bottom_left_corner != se)
-		A.cut_overlay(A.bottom_left_corner)
-		A.bottom_left_corner = se
-		LAZYADD(New, se)
+	if(bottom_left_corner != se)
+		cut_overlay(bottom_left_corner)
+		bottom_left_corner = se
+		LAZYADD(new_overlays, se)
 
-	if(New)
-		A.add_overlay(New)
+	if(new_overlays)
+		add_overlay(new_overlays)
 
-/proc/find_type_in_direction(atom/source, direction)
-	var/turf/target_turf = get_step(source, direction)
+
+///Scans direction to find targets to smooth with.
+/atom/proc/find_type_in_direction(direction)
+	var/turf/target_turf = get_step(src, direction)
 	if(!target_turf)
 		return NULLTURF_BORDER
 
 	var/area/target_area = get_area(target_turf)
-	var/area/source_area = get_area(source)
+	var/area/source_area = get_area(src)
 	if((source_area.area_limited_icon_smoothing || target_area.area_limited_icon_smoothing) && !istype(source_area, target_area.type) && !istype(target_area, source_area.type))
-		return null
+		return NO_ADJ_FOUND
 
-	if(source.canSmoothWith)
-		var/atom/A
-		if(source.smoothing_flags & SMOOTH_MORE)
-			for(var/a_type in source.canSmoothWith)
-				if( istype(target_turf, a_type) )
-					return target_turf
-				A = locate(a_type) in target_turf
-				if(A)
-					return A
-			return null
+	if(isnull(canSmoothWith)) //special case in which it will only smooth with itself
+		if(isturf(src))
+			return (type == target_turf.type) ? ADJ_FOUND : NO_ADJ_FOUND
+		var/atom/matching_obj = locate(type) in target_turf
+		return (matching_obj && matching_obj.type == type) ? ADJ_FOUND : NO_ADJ_FOUND
+
+	if(!isnull(target_turf.smoothing_groups))
+		for(var/target in canSmoothWith)
+			if(!(canSmoothWith[target] & target_turf.smoothing_groups[target]))
+				continue
+			return ADJ_FOUND
+
+	if(smoothing_flags & SMOOTH_OBJ)
+		for(var/am in target_turf)
+			var/atom/movable/thing = am
+			if(!thing.anchored || isnull(thing.smoothing_groups))
+				continue
+			for(var/target in canSmoothWith)
+				if(!(canSmoothWith[target] & thing.smoothing_groups[target]))
+					continue
+				return ADJ_FOUND
+
+	return NO_ADJ_FOUND
 
-		for(var/a_type in source.canSmoothWith)
-			if(a_type == target_turf.type)
-				return target_turf
-			A = locate(a_type) in target_turf
-			if(A && A.type == a_type)
-				return A
-		return null
-	else
-		if(isturf(source))
-			return source.type == target_turf.type ? target_turf : null
-		var/atom/A = locate(source.type) in target_turf
-		return A && A.type == source.type ? A : null
 
 //Icon smoothing helpers
 /proc/smooth_zlevel(zlevel, now = FALSE)
@@ -299,17 +296,18 @@
 		var/turf/T = V
 		if(T.smoothing_flags)
 			if(now)
-				smooth_icon(T)
+				T.smooth_icon()
 			else
 				QUEUE_SMOOTH(T)
 		for(var/R in T)
 			var/atom/A = R
 			if(A.smoothing_flags)
 				if(now)
-					smooth_icon(A)
+					A.smooth_icon()
 				else
 					QUEUE_SMOOTH(A)
 
+
 /atom/proc/clear_smooth_overlays()
 	cut_overlay(top_left_corner)
 	top_left_corner = null
@@ -320,6 +318,7 @@
 	cut_overlay(bottom_left_corner)
 	bottom_left_corner = null
 
+
 /atom/proc/replace_smooth_overlays(nw, ne, sw, se)
 	clear_smooth_overlays()
 	var/list/O = list()
@@ -333,6 +332,7 @@
 	O += se
 	add_overlay(O)
 
+
 /proc/reverse_ndir(ndir)
 	switch(ndir)
 		if(N_NORTH)
@@ -368,7 +368,7 @@
 		if(N_SOUTH|N_EAST|N_SOUTHEAST)
 			return SOUTHEAST
 		else
-			return 0
+			return NONE
 
 
 //Example smooth wall
@@ -376,5 +376,22 @@
 	name = "smooth wall"
 	icon = 'icons/turf/smooth_wall.dmi'
 	icon_state = "smooth"
-	smoothing_flags = SMOOTH_TRUE|SMOOTH_DIAGONAL|SMOOTH_BORDER
+	smoothing_flags = SMOOTH_CORNERS|SMOOTH_DIAGONAL|SMOOTH_BORDER
+	smoothing_groups = null
 	canSmoothWith = null
+
+#undef N_NORTH
+#undef N_SOUTH
+#undef N_EAST
+#undef N_WEST
+#undef N_NORTHEAST
+#undef N_NORTHWEST
+#undef N_SOUTHEAST
+#undef N_SOUTHWEST
+
+#undef NO_ADJ_FOUND
+#undef ADJ_FOUND
+#undef NULLTURF_BORDER
+
+#undef DEFAULT_UNDERLAY_ICON
+#undef DEFAULT_UNDERLAY_ICON_STATE

code/_globalvars/bitfields.dm

@@ -176,8 +176,7 @@ GLOBAL_LIST_INIT(bitfields, list(
 		"ZAP_MACHINE_EXPLOSIVE" = ZAP_MACHINE_EXPLOSIVE,
 		),
 	"smooth" = list(
-		"SMOOTH_TRUE" = SMOOTH_TRUE,
-		"SMOOTH_MORE" = SMOOTH_MORE,
+		"SMOOTH_CORNERS" = SMOOTH_CORNERS,
 		"SMOOTH_DIAGONAL" = SMOOTH_DIAGONAL,
 		"SMOOTH_BORDER" = SMOOTH_BORDER,
 		"SMOOTH_QUEUED" = SMOOTH_QUEUED,

code/controllers/subsystem/icon_smooth.dm

@@ -18,7 +18,7 @@ SUBSYSTEM_DEF(icon_smooth)
 		if(QDELETED(smoothing_atom) || !(smoothing_atom.smoothing_flags & SMOOTH_QUEUED))
 			continue
 		if(smoothing_atom.flags_1 & INITIALIZED_1)
-			smooth_icon(smoothing_atom)
+			smoothing_atom.smooth_icon()
 		else
 			deferred += smoothing_atom
 		if (MC_TICK_CHECK)
@@ -32,8 +32,8 @@ SUBSYSTEM_DEF(icon_smooth)
 			can_fire = FALSE
 
 /datum/controller/subsystem/icon_smooth/Initialize()
-	smooth_zlevel(1,TRUE)
-	smooth_zlevel(2,TRUE)
+	smooth_zlevel(1, TRUE)
+	smooth_zlevel(2, TRUE)
 
 	var/list/queue = smooth_queue
 	smooth_queue = list()
@@ -43,7 +43,7 @@ SUBSYSTEM_DEF(icon_smooth)
 		queue.len--
 		if(QDELETED(smoothing_atom) || !(smoothing_atom.smoothing_flags & SMOOTH_QUEUED) || smoothing_atom.z <= 2)
 			continue
-		smooth_icon(smoothing_atom)
+		smoothing_atom.smooth_icon()
 		CHECK_TICK
 
 	queue = blueprint_queue

code/game/atoms.dm

@@ -122,7 +122,9 @@
 	var/bottom_left_corner
 	///Smoothing variable
 	var/bottom_right_corner
-	///Type path list this atom can smooth with. If this is null and atom is smooth, it smooths only with itself.
+	///What smoothing groups does this atom belongs to, to match canSmoothWith. If null, nobody can smooth with it.
+	var/list/smoothing_groups = null
+	///List of smoothing groups this atom can smooth with. If this is null and atom is smooth, it smooths only with itself.
 	var/list/canSmoothWith = null
 
 
@@ -206,8 +208,14 @@
 		var/turf/T = loc
 		T.has_opaque_atom = TRUE // No need to recalculate it in this case, it's guaranteed to be on afterwards anyways.
 
-	if (canSmoothWith)
-		canSmoothWith = typelist("canSmoothWith", canSmoothWith)
+	if (length(smoothing_groups))
+		sortTim(smoothing_groups) //In case it's not properly ordered, let's avoid duplicate entries with the same values.
+		SET_BITFLAG_LIST(smoothing_groups)
+	if (length(canSmoothWith))
+		sortTim(canSmoothWith)
+		if(canSmoothWith[length(canSmoothWith)] > MAX_S_TURF) //If the last element is higher than the maximum turf-only value, then it must scan turf contents for smoothing targets.
+			smoothing_flags |= SMOOTH_OBJ
+		SET_BITFLAG_LIST(canSmoothWith)
 
 	// apply materials properly from the default custom_materials value
 	set_custom_materials(custom_materials)

code/game/machinery/deployable.dm

@@ -107,8 +107,9 @@
 	pass_flags = LETPASSTHROW
 	bar_material = SAND
 	climbable = TRUE
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/barricade/sandbags, /turf/closed/wall, /turf/closed/wall/r_wall, /obj/structure/falsewall, /obj/structure/falsewall/reinforced, /turf/closed/wall/rust, /turf/closed/wall/r_wall/rust, /obj/structure/barricade/security)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_SANDBAGS)
+	canSmoothWith = list(SMOOTH_GROUP_SANDBAGS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SECURITY_BARRICADE)
 
 
 /obj/structure/barricade/security

code/game/objects/effects/decals/cleanable/misc.dm

@@ -53,8 +53,9 @@
 	name = "dirt"
 	desc = "Someone should clean that up."
 	icon_state = "dirt"
-	canSmoothWith = list(/obj/effect/decal/cleanable/dirt, /turf/closed/wall, /obj/structure/falsewall)
 	smoothing_flags = NONE
+	smoothing_groups = list(SMOOTH_GROUP_CLEANABLE_DIRT)
+	canSmoothWith = list(SMOOTH_GROUP_CLEANABLE_DIRT, SMOOTH_GROUP_WALLS)
 	mouse_opacity = MOUSE_OPACITY_TRANSPARENT
 	beauty = -75
 
@@ -62,7 +63,7 @@
 	. = ..()
 	var/turf/T = get_turf(src)
 	if(T.tiled_dirt)
-		smoothing_flags = SMOOTH_MORE
+		smoothing_flags = SMOOTH_CORNERS
 		icon = 'icons/effects/dirt.dmi'
 		icon_state = ""
 		QUEUE_SMOOTH(src)

code/game/objects/structures/aliens.dm

@@ -57,9 +57,10 @@
 	density = TRUE
 	opacity = 1
 	anchored = TRUE
-	canSmoothWith = list(/obj/structure/alien/resin)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_ALIEN_RESIN)
+	canSmoothWith = list(SMOOTH_GROUP_ALIEN_RESIN)
 	max_integrity = 200
-	smoothing_flags = SMOOTH_TRUE
 	var/resintype = null
 	CanAtmosPass = ATMOS_PASS_DENSITY
 
@@ -79,7 +80,8 @@
 	icon = 'icons/obj/smooth_structures/alien/resin_wall.dmi'
 	icon_state = "smooth"	//same as resin, but consistency ho!
 	resintype = "wall"
-	canSmoothWith = list(/obj/structure/alien/resin/wall, /obj/structure/alien/resin/membrane)
+	smoothing_groups = list(SMOOTH_GROUP_ALIEN_RESIN, SMOOTH_GROUP_ALIEN_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_ALIEN_WALLS)
 
 /obj/structure/alien/resin/wall/BlockSuperconductivity()
 	return 1
@@ -92,7 +94,8 @@
 	opacity = 0
 	max_integrity = 160
 	resintype = "membrane"
-	canSmoothWith = list(/obj/structure/alien/resin/wall, /obj/structure/alien/resin/membrane)
+	smoothing_groups = list(SMOOTH_GROUP_ALIEN_RESIN, SMOOTH_GROUP_ALIEN_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_ALIEN_WALLS)
 
 /obj/structure/alien/resin/attack_paw(mob/user)
 	return attack_hand(user)
@@ -113,8 +116,9 @@
 	plane = FLOOR_PLANE
 	icon_state = "weeds"
 	max_integrity = 15
-	canSmoothWith = list(/obj/structure/alien/weeds, /turf/closed/wall)
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_ALIEN_RESIN, SMOOTH_GROUP_ALIEN_WEEDS)
+	canSmoothWith = list(SMOOTH_GROUP_ALIEN_WEEDS, SMOOTH_GROUP_WALLS)
 	var/last_expand = 0 //last world.time this weed expanded
 	var/growth_cooldown_low = 150
 	var/growth_cooldown_high = 200

code/game/objects/structures/beds_chairs/alien_nest.dm

@@ -6,8 +6,8 @@
 	icon = 'icons/obj/smooth_structures/alien/nest.dmi'
 	icon_state = "nest"
 	max_integrity = 120
-	smoothing_flags = SMOOTH_TRUE
 	can_be_unanchored = FALSE
+	smoothing_flags = SMOOTH_CORNERS
 	canSmoothWith = null
 	buildstacktype = null
 	flags_1 = NODECONSTRUCT_1

code/game/objects/structures/false_walls.dm

@@ -11,15 +11,9 @@
 	density = TRUE
 	opacity = 1
 	max_integrity = 100
-
-	canSmoothWith = list(
-		/turf/closed/wall,
-		/turf/closed/wall/r_wall,
-		/obj/structure/falsewall,
-		/obj/structure/falsewall/reinforced,
-		/turf/closed/wall/rust,
-		/turf/closed/wall/r_wall/rust)
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_WALLS)
 	can_be_unanchored = FALSE
 	CanAtmosPass = ATMOS_PASS_DENSITY
 	flags_1 = RAD_PROTECT_CONTENTS_1 | RAD_NO_CONTAMINATE_1
@@ -70,7 +64,7 @@
 	else
 		if(density)
 			icon_state = initial(icon_state)
-			smoothing_flags = SMOOTH_TRUE
+			smoothing_flags = SMOOTH_CORNERS
 			QUEUE_SMOOTH(src)
 		else
 			icon_state = "fwall_open"
@@ -163,9 +157,10 @@
 	icon_state = "uranium"
 	mineral = /obj/item/stack/sheet/mineral/uranium
 	walltype = /turf/closed/wall/mineral/uranium
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_URANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_URANIUM_WALLS)
 	var/active = null
 	var/last_event = 0
-	canSmoothWith = list(/obj/structure/falsewall/uranium, /turf/closed/wall/mineral/uranium)
 
 /obj/structure/falsewall/uranium/attackby(obj/item/W, mob/user, params)
 	radiate()
@@ -197,7 +192,8 @@
 	icon_state = "gold"
 	mineral = /obj/item/stack/sheet/mineral/gold
 	walltype = /turf/closed/wall/mineral/gold
-	canSmoothWith = list(/obj/structure/falsewall/gold, /turf/closed/wall/mineral/gold)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_GOLD_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_GOLD_WALLS)
 
 /obj/structure/falsewall/silver
 	name = "silver wall"
@@ -206,7 +202,8 @@
 	icon_state = "silver"
 	mineral = /obj/item/stack/sheet/mineral/silver
 	walltype = /turf/closed/wall/mineral/silver
-	canSmoothWith = list(/obj/structure/falsewall/silver, /turf/closed/wall/mineral/silver)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SILVER_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SILVER_WALLS)
 
 /obj/structure/falsewall/diamond
 	name = "diamond wall"
@@ -215,7 +212,8 @@
 	icon_state = "diamond"
 	mineral = /obj/item/stack/sheet/mineral/diamond
 	walltype = /turf/closed/wall/mineral/diamond
-	canSmoothWith = list(/obj/structure/falsewall/diamond, /turf/closed/wall/mineral/diamond)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_DIAMOND_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_DIAMOND_WALLS)
 	max_integrity = 800
 
 /obj/structure/falsewall/plasma
@@ -225,7 +223,8 @@
 	icon_state = "plasma"
 	mineral = /obj/item/stack/sheet/mineral/plasma
 	walltype = /turf/closed/wall/mineral/plasma
-	canSmoothWith = list(/obj/structure/falsewall/plasma, /turf/closed/wall/mineral/plasma)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_PLASMA_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_PLASMA_WALLS)
 
 /obj/structure/falsewall/plasma/attackby(obj/item/W, mob/user, params)
 	if(W.get_temperature() > 300)
@@ -253,7 +252,8 @@
 	icon_state = "bananium"
 	mineral = /obj/item/stack/sheet/mineral/bananium
 	walltype = /turf/closed/wall/mineral/bananium
-	canSmoothWith = list(/obj/structure/falsewall/bananium, /turf/closed/wall/mineral/bananium)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_BANANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_BANANIUM_WALLS)
 
 
 /obj/structure/falsewall/sandstone
@@ -263,7 +263,8 @@
 	icon_state = "sandstone"
 	mineral = /obj/item/stack/sheet/mineral/sandstone
 	walltype = /turf/closed/wall/mineral/sandstone
-	canSmoothWith = list(/obj/structure/falsewall/sandstone, /turf/closed/wall/mineral/sandstone)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SANDSTONE_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SANDSTONE_WALLS)
 
 /obj/structure/falsewall/wood
 	name = "wooden wall"
@@ -272,7 +273,8 @@
 	icon_state = "wood"
 	mineral = /obj/item/stack/sheet/mineral/wood
 	walltype = /turf/closed/wall/mineral/wood
-	canSmoothWith = list(/obj/structure/falsewall/wood, /turf/closed/wall/mineral/wood)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_WOOD_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_WOOD_WALLS)
 
 /obj/structure/falsewall/iron
 	name = "rough metal wall"
@@ -282,7 +284,8 @@
 	mineral = /obj/item/stack/rods
 	mineral_amount = 5
 	walltype = /turf/closed/wall/mineral/iron
-	canSmoothWith = list(/obj/structure/falsewall/iron, /turf/closed/wall/mineral/iron)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_IRON_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_IRON_WALLS)
 
 /obj/structure/falsewall/abductor
 	name = "alien wall"
@@ -291,7 +294,8 @@
 	icon_state = "abductor"
 	mineral = /obj/item/stack/sheet/mineral/abductor
 	walltype = /turf/closed/wall/mineral/abductor
-	canSmoothWith = list(/obj/structure/falsewall/abductor, /turf/closed/wall/mineral/abductor)
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_ABDUCTOR_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_ABDUCTOR_WALLS)
 
 /obj/structure/falsewall/titanium
 	name = "wall"
@@ -300,8 +304,9 @@
 	icon_state = "shuttle"
 	mineral = /obj/item/stack/sheet/mineral/titanium
 	walltype = /turf/closed/wall/mineral/titanium
-	smoothing_flags = SMOOTH_MORE
-	canSmoothWith = list(/turf/closed/wall/mineral/titanium, /obj/machinery/door/airlock/shuttle, /obj/machinery/door/airlock, /obj/structure/window/shuttle, /obj/structure/shuttle/engine/heater)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_TITANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_TITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /obj/structure/falsewall/plastitanium
 	name = "wall"
@@ -310,5 +315,6 @@
 	icon_state = "shuttle"
 	mineral = /obj/item/stack/sheet/mineral/plastitanium
 	walltype = /turf/closed/wall/mineral/plastitanium
-	smoothing_flags = SMOOTH_MORE
-	canSmoothWith = list(/turf/closed/wall/mineral/plastitanium, /obj/machinery/door/airlock/shuttle, /obj/machinery/door/airlock, /obj/structure/window/shuttle, /obj/structure/shuttle/engine/heater)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WALLS, SMOOTH_GROUP_PLASTITANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_PLASTITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)

code/game/objects/structures/fluff.dm

@@ -253,8 +253,9 @@
 	desc = "A large bushy hedge."
 	icon = 'icons/obj/smooth_structures/hedge.dmi'
 	icon_state = "hedge"
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/fluff/hedge, /obj/structure/fluff/hedge/opaque)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_HEDGE_FLUFF)
+	canSmoothWith = list(SMOOTH_GROUP_HEDGE_FLUFF)
 	density = TRUE
 	anchored = TRUE
 	deconstructible = FALSE

code/game/objects/structures/lattice.dm

@@ -9,15 +9,13 @@
 	max_integrity = 50
 	layer = LATTICE_LAYER //under pipes
 	plane = FLOOR_PLANE
+	obj_flags = CAN_BE_HIT | BLOCK_Z_OUT_DOWN
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_LATTICE)
+	canSmoothWith = list(SMOOTH_GROUP_LATTICE, SMOOTH_GROUP_OPEN_FLOOR, SMOOTH_GROUP_WALLS)
 	var/number_of_mats = 1
 	var/build_material = /obj/item/stack/rods
-	canSmoothWith = list(/obj/structure/lattice,
-	/turf/open/floor,
-	/turf/closed/wall,
-	/obj/structure/falsewall)
-	smoothing_flags = SMOOTH_MORE
-	//	flags = CONDUCT_1
-	obj_flags = CAN_BE_HIT | BLOCK_Z_OUT_DOWN
+
 
 /obj/structure/lattice/examine(mob/user)
 	. = ..()
@@ -76,7 +74,8 @@
 	icon = 'icons/obj/smooth_structures/catwalk.dmi'
 	icon_state = "catwalk"
 	number_of_mats = 2
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = null
 	canSmoothWith = null
 	obj_flags = CAN_BE_HIT | BLOCK_Z_OUT_DOWN | BLOCK_Z_IN_UP
 
@@ -102,7 +101,8 @@
 	icon_state = "catwalk"
 	number_of_mats = 1
 	color = "#5286b9ff"
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = null
 	canSmoothWith = null
 	obj_flags = CAN_BE_HIT | BLOCK_Z_OUT_DOWN | BLOCK_Z_IN_UP
 	resistance_flags = FIRE_PROOF | LAVA_PROOF

code/game/objects/structures/tables_racks.dm

@@ -32,8 +32,9 @@
 	custom_materials = list(/datum/material/iron = 2000)
 	max_integrity = 100
 	integrity_failure = 0.33
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/table, /obj/structure/table/reinforced, /obj/structure/table/greyscale)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_TABLES)
+	canSmoothWith = list(SMOOTH_GROUP_TABLES)
 
 /obj/structure/table/examine(mob/user)
 	. = ..()
@@ -266,7 +267,8 @@
 	desc = "An NT brand \"Rolly poly\" rolling table. It can and will move."
 	anchored = FALSE
 	smoothing_flags = NONE
-	canSmoothWith = list()
+	smoothing_groups = null
+	canSmoothWith = null
 	icon = 'icons/obj/smooth_structures/rollingtable.dmi'
 	icon_state = "rollingtable"
 	var/list/attached_items = list()
@@ -300,6 +302,7 @@
 	icon = 'icons/obj/smooth_structures/glass_table.dmi'
 	icon_state = "glass_table"
 	buildstack = /obj/item/stack/sheet/glass
+	smoothing_groups = null
 	canSmoothWith = null
 	max_integrity = 70
 	resistance_flags = ACID_PROOF
@@ -382,9 +385,8 @@
 	buildstack = /obj/item/stack/sheet/mineral/wood
 	resistance_flags = FLAMMABLE
 	max_integrity = 70
-	canSmoothWith = list(/obj/structure/table/wood,
-		/obj/structure/table/wood/poker,
-		/obj/structure/table/wood/bar)
+	smoothing_groups = list(SMOOTH_GROUP_WOOD_TABLES) //Don't smooth with SMOOTH_GROUP_TABLES
+	canSmoothWith = list(SMOOTH_GROUP_WOOD_TABLES)
 
 /obj/structure/table/wood/narsie_act(total_override = TRUE)
 	if(!total_override)
@@ -408,16 +410,8 @@
 	frame = /obj/structure/table_frame
 	framestack = /obj/item/stack/rods
 	buildstack = /obj/item/stack/tile/carpet
-	canSmoothWith = list(/obj/structure/table/wood/fancy,
-		/obj/structure/table/wood/fancy/black,
-		/obj/structure/table/wood/fancy/blue,
-		/obj/structure/table/wood/fancy/cyan,
-		/obj/structure/table/wood/fancy/green,
-		/obj/structure/table/wood/fancy/orange,
-		/obj/structure/table/wood/fancy/purple,
-		/obj/structure/table/wood/fancy/red,
-		/obj/structure/table/wood/fancy/royalblack,
-		/obj/structure/table/wood/fancy/royalblue)
+	smoothing_groups = list(SMOOTH_GROUP_FANCY_WOOD_TABLES) //Don't smooth with SMOOTH_GROUP_TABLES or SMOOTH_GROUP_WOOD_TABLES
+	canSmoothWith = list(SMOOTH_GROUP_FANCY_WOOD_TABLES)
 	var/smooth_icon = 'icons/obj/smooth_structures/fancy_table.dmi' // see Initialize()
 
 /obj/structure/table/wood/fancy/Initialize()
@@ -483,7 +477,6 @@
 	icon_state = "r_table"
 	deconstruction_ready = 0
 	buildstack = /obj/item/stack/sheet/plasteel
-	canSmoothWith = list(/obj/structure/table/reinforced, /obj/structure/table, /obj/structure/table/reinforced/ctf)
 	max_integrity = 200
 	integrity_failure = 0.25
 	armor = list("melee" = 10, "bullet" = 30, "laser" = 30, "energy" = 100, "bomb" = 20, "bio" = 0, "rad" = 0, "fire" = 80, "acid" = 70)
@@ -519,7 +512,8 @@
 	icon_state = "brass_table"
 	resistance_flags = FIRE_PROOF | ACID_PROOF
 	buildstack = /obj/item/stack/tile/bronze
-	canSmoothWith = list(/obj/structure/table/bronze)
+	smoothing_groups = list(SMOOTH_GROUP_BRONZE_TABLES) //Don't smooth with SMOOTH_GROUP_TABLES
+	canSmoothWith = list(SMOOTH_GROUP_BRONZE_TABLES)
 
 /obj/structure/table/bronze/tablepush(mob/living/user, mob/living/pushed_mob)
 	..()

code/game/objects/structures/window.dm

@@ -590,8 +590,9 @@
 	max_integrity = 50
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
+	canSmoothWith = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	glass_amount = 2
 
 /obj/structure/window/fulltile/unanchored
@@ -604,8 +605,9 @@
 	max_integrity = 300
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
+	canSmoothWith = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	glass_amount = 2
 
 /obj/structure/window/plasma/fulltile/unanchored
@@ -619,7 +621,9 @@
 	max_integrity = 1000
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
+	canSmoothWith = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	glass_amount = 2
 
 /obj/structure/window/plasma/reinforced/fulltile/unanchored
@@ -633,9 +637,10 @@
 	max_integrity = 150
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
 	state = RWINDOW_SECURE
-	canSmoothWith = list(/obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
+	canSmoothWith = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	glass_amount = 2
 
 /obj/structure/window/reinforced/fulltile/unanchored
@@ -648,15 +653,15 @@
 	dir = FULLTILE_WINDOW_DIR
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
+	canSmoothWith = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	glass_amount = 2
 
 /obj/structure/window/reinforced/fulltile/ice
 	icon = 'icons/obj/smooth_structures/rice_window.dmi'
 	icon_state = "ice_window"
 	max_integrity = 150
-	canSmoothWith = list(/obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/plasma/fulltile, /obj/structure/window/plasma/reinforced/fulltile)
 	glass_amount = 2
 
 /obj/structure/window/shuttle
@@ -672,7 +677,8 @@
 	reinf = TRUE
 	heat_resistance = 1600
 	armor = list("melee" = 90, "bullet" = 0, "laser" = 0, "energy" = 0, "bomb" = 50, "bio" = 100, "rad" = 100, "fire" = 80, "acid" = 100)
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_SHUTTLE_PARTS)
 	canSmoothWith = null
 	explosion_block = 3
 	glass_type = /obj/item/stack/sheet/titaniumglass
@@ -700,7 +706,8 @@
 	flags_1 = PREVENT_CLICK_UNDER_1
 	heat_resistance = 1600
 	armor = list("melee" = 95, "bullet" = 0, "laser" = 0, "energy" = 0, "bomb" = 50, "bio" = 100, "rad" = 100, "fire" = 80, "acid" = 100)
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	canSmoothWith = null
 	explosion_block = 3
 	damage_deflection = 11 //The same as normal reinforced windows.3
@@ -722,8 +729,9 @@
 	max_integrity = 15
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/obj/structure/window/paperframe, /obj/structure/mineral_door/paperframe)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_PAPERFRAME)
+	canSmoothWith = list(SMOOTH_GROUP_PAPERFRAME)
 	glass_amount = 2
 	glass_type = /obj/item/stack/sheet/paperframes
 	heat_resistance = 233
@@ -808,7 +816,8 @@
 
 /obj/structure/window/bronze/fulltile
 	icon_state = "clockwork_window"
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_WINDOW_FULLTILE)
 	canSmoothWith = null
 	fulltile = TRUE
 	flags_1 = PREVENT_CLICK_UNDER_1

code/game/turfs/closed/_closed.dm

@@ -50,7 +50,7 @@
 	icon = 'icons/turf/walls/sandstone_wall.dmi'
 	icon_state = "sandstone"
 	baseturfs = /turf/closed/indestructible/sandstone
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 
 /turf/closed/indestructible/oldshuttle/corner
 	icon_state = "corner"
@@ -79,12 +79,14 @@
 /turf/closed/indestructible/riveted
 	icon = 'icons/turf/walls/riveted.dmi'
 	icon_state = "riveted"
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 
 /turf/closed/indestructible/syndicate
 	icon = 'icons/turf/walls/plastitanium_wall.dmi'
 	icon_state = "map-shuttle"
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SYNDICATE_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SYNDICATE_WALLS, SMOOTH_GROUP_PLASTITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /turf/closed/indestructible/riveted/uranium
 	icon = 'icons/turf/walls/uranium_wall.dmi'
@@ -99,7 +101,9 @@
 /turf/closed/indestructible/wood
 	icon = 'icons/turf/walls/wood_wall.dmi'
 	icon_state = "wood"
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_WOOD_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_WOOD_WALLS)
 
 /turf/closed/indestructible/abductor
 	icon_state = "alien1"
@@ -111,7 +115,7 @@
 	name = "window"
 	icon_state = "fake_window"
 	opacity = 0
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 	icon = 'icons/obj/smooth_structures/reinforced_window.dmi'
 
 /turf/closed/indestructible/fakeglass/Initialize()
@@ -124,7 +128,7 @@
 	name = "window"
 	icon_state = "plastitanium_window"
 	opacity = 0
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 	icon = 'icons/obj/smooth_structures/plastitanium_window.dmi'
 
 /turf/closed/indestructible/opsglass/Initialize()
@@ -161,8 +165,8 @@
 /turf/closed/indestructible/rock/snow/ice/ore
 	icon = 'icons/turf/walls/icerock_wall.dmi'
 	icon_state = "icerock"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	canSmoothWith = list(SMOOTH_GROUP_CLOSED_TURFS)
 	pixel_x = -4
 	pixel_y = -4
 
@@ -191,7 +195,8 @@
 	desc = "A thick, seemingly indestructible stone wall."
 	icon = 'icons/turf/walls/boss_wall.dmi'
 	icon_state = "wall"
-	canSmoothWith = list(/turf/closed/indestructible/riveted/boss, /turf/closed/indestructible/riveted/boss/see_through)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_BOSS_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_BOSS_WALLS)
 	explosion_block = 50
 	baseturfs = /turf/closed/indestructible/riveted/boss
 

code/game/turfs/closed/minerals.dm

@@ -5,8 +5,9 @@
 	icon = 'icons/turf/mining.dmi'
 	icon_state = "rock"
 	var/smooth_icon = 'icons/turf/smoothrocks.dmi'
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = null
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_MINERAL_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_MINERAL_WALLS)
 	baseturfs = /turf/open/floor/plating/asteroid/airless
 	initial_gas_mix = AIRLESS_ATMOS
 	opacity = 1
@@ -22,13 +23,12 @@
 	var/defer_change = 0
 
 /turf/closed/mineral/Initialize()
-	if (!canSmoothWith)
-		canSmoothWith = list(/turf/closed/mineral, /turf/closed/indestructible)
+	. = ..()
 	var/matrix/M = new
 	M.Translate(-4, -4)
 	transform = M
 	icon = smooth_icon
-	. = ..()
+
 
 /turf/closed/mineral/proc/Spread_Vein()
 	var/spreadChance = initial(mineralType.spreadChance)
@@ -254,8 +254,8 @@
 	icon = 'icons/turf/mining.dmi'
 	smooth_icon = 'icons/turf/walls/mountain_wall.dmi'
 	icon_state = "mountainrock"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	canSmoothWith = list(SMOOTH_GROUP_CLOSED_TURFS)
 	defer_change = TRUE
 	environment_type = "snow_cavern"
 	turf_type = /turf/open/floor/plating/asteroid/snow/icemoon
@@ -323,8 +323,8 @@
 	icon = 'icons/turf/mining.dmi'
 	smooth_icon = 'icons/turf/walls/mountain_wall.dmi'
 	icon_state = "mountainrock"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	canSmoothWith = list(SMOOTH_GROUP_CLOSED_TURFS)
 	defer_change = TRUE
 	environment_type = "snow"
 	turf_type = /turf/open/floor/plating/asteroid/snow/icemoon
@@ -574,8 +574,8 @@
 	icon = 'icons/turf/mining.dmi'
 	smooth_icon = 'icons/turf/walls/rock_wall.dmi'
 	icon_state = "rock2"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	canSmoothWith = list(SMOOTH_GROUP_CLOSED_TURFS)
 	baseturfs = /turf/open/floor/plating/ashplanet/wateryrock
 	initial_gas_mix = OPENTURF_LOW_PRESSURE
 	environment_type = "waste"
@@ -587,8 +587,8 @@
 	icon = 'icons/turf/mining.dmi'
 	smooth_icon = 'icons/turf/walls/mountain_wall.dmi'
 	icon_state = "mountainrock"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	canSmoothWith = list(SMOOTH_GROUP_CLOSED_TURFS)
 	baseturfs = /turf/open/floor/plating/asteroid/snow
 	initial_gas_mix = FROZEN_ATMOS
 	environment_type = "snow"
@@ -605,8 +605,7 @@
 	icon = 'icons/turf/mining.dmi'
 	smooth_icon = 'icons/turf/walls/icerock_wall.dmi'
 	icon_state = "icerock"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
-	canSmoothWith = list (/turf/closed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
 	baseturfs = /turf/open/floor/plating/asteroid/snow/ice
 	environment_type = "snow_cavern"
 	turf_type = /turf/open/floor/plating/asteroid/snow/ice

code/game/turfs/closed/wall/material_walls.dm

@@ -3,8 +3,9 @@
 	desc = "A huge chunk of material used to separate rooms."
 	icon = 'icons/turf/walls/materialwall.dmi'
 	icon_state = "wall"
-	canSmoothWith = list(/turf/closed/wall/material)
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_MATERIAL_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_MATERIAL_WALLS)
 	material_flags = MATERIAL_ADD_PREFIX | MATERIAL_COLOR | MATERIAL_AFFECT_STATISTICS
 
 /turf/closed/wall/material/break_wall()

code/game/turfs/closed/wall/mineral_walls.dm

@@ -2,10 +2,10 @@
 	name = "mineral wall"
 	desc = "This shouldn't exist"
 	icon_state = ""
+	smoothing_flags = SMOOTH_CORNERS
+	canSmoothWith = null
 	var/last_event = 0
 	var/active = null
-	canSmoothWith = null
-	smoothing_flags = SMOOTH_TRUE
 
 /turf/closed/wall/mineral/gold
 	name = "gold wall"
@@ -14,7 +14,8 @@
 	icon_state = "gold"
 	sheet_type = /obj/item/stack/sheet/mineral/gold
 	explosion_block = 0 //gold is a soft metal you dingus.
-	canSmoothWith = list(/turf/closed/wall/mineral/gold, /obj/structure/falsewall/gold)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_GOLD_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_GOLD_WALLS)
 
 /turf/closed/wall/mineral/silver
 	name = "silver wall"
@@ -22,7 +23,8 @@
 	icon = 'icons/turf/walls/silver_wall.dmi'
 	icon_state = "silver"
 	sheet_type = /obj/item/stack/sheet/mineral/silver
-	canSmoothWith = list(/turf/closed/wall/mineral/silver, /obj/structure/falsewall/silver)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SILVER_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SILVER_WALLS)
 
 /turf/closed/wall/mineral/diamond
 	name = "diamond wall"
@@ -32,7 +34,8 @@
 	sheet_type = /obj/item/stack/sheet/mineral/diamond
 	slicing_duration = 200   //diamond wall takes twice as much time to slice
 	explosion_block = 3
-	canSmoothWith = list(/turf/closed/wall/mineral/diamond, /obj/structure/falsewall/diamond)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_DIAMOND_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_DIAMOND_WALLS)
 
 /turf/closed/wall/mineral/diamond/hulk_recoil(obj/item/bodypart/arm, mob/living/carbon/human/hulkman, damage = 41)
 	return ..()
@@ -43,7 +46,8 @@
 	icon = 'icons/turf/walls/bananium_wall.dmi'
 	icon_state = "bananium"
 	sheet_type = /obj/item/stack/sheet/mineral/bananium
-	canSmoothWith = list(/turf/closed/wall/mineral/bananium, /obj/structure/falsewall/bananium)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_BANANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_BANANIUM_WALLS)
 
 /turf/closed/wall/mineral/sandstone
 	name = "sandstone wall"
@@ -52,7 +56,8 @@
 	icon_state = "sandstone"
 	sheet_type = /obj/item/stack/sheet/mineral/sandstone
 	explosion_block = 0
-	canSmoothWith = list(/turf/closed/wall/mineral/sandstone, /obj/structure/falsewall/sandstone)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SANDSTONE_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SANDSTONE_WALLS)
 
 /turf/closed/wall/mineral/uranium
 	article = "a"
@@ -61,7 +66,8 @@
 	icon = 'icons/turf/walls/uranium_wall.dmi'
 	icon_state = "uranium"
 	sheet_type = /obj/item/stack/sheet/mineral/uranium
-	canSmoothWith = list(/turf/closed/wall/mineral/uranium, /obj/structure/falsewall/uranium)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_URANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_URANIUM_WALLS)
 
 /turf/closed/wall/mineral/uranium/proc/radiate()
 	if(!active)
@@ -97,7 +103,8 @@
 	icon_state = "plasma"
 	sheet_type = /obj/item/stack/sheet/mineral/plasma
 	thermal_conductivity = 0.04
-	canSmoothWith = list(/turf/closed/wall/mineral/plasma, /obj/structure/falsewall/plasma)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_PLASMA_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_PLASMA_WALLS)
 
 /turf/closed/wall/mineral/plasma/attackby(obj/item/W, mob/user, params)
 	if(W.get_temperature() > 300)//If the temperature of the object is over 300, then ignite
@@ -136,7 +143,8 @@
 	sheet_type = /obj/item/stack/sheet/mineral/wood
 	hardness = 70
 	explosion_block = 0
-	canSmoothWith = list(/turf/closed/wall/mineral/wood, /obj/structure/falsewall/wood, /turf/closed/wall/mineral/wood/nonmetal)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_WOOD_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_WOOD_WALLS)
 
 /turf/closed/wall/mineral/wood/attackby(obj/item/W, mob/user)
 	if(W.get_sharpness() && W.force)
@@ -155,7 +163,6 @@
 	desc = "A solidly wooden wall. It's a bit weaker than a wall made with metal."
 	girder_type = /obj/structure/barricade/wooden
 	hardness = 50
-	canSmoothWith = list(/turf/closed/wall/mineral/wood, /obj/structure/falsewall/wood, /turf/closed/wall/mineral/wood/nonmetal)
 
 /turf/closed/wall/mineral/iron
 	name = "rough metal wall"
@@ -163,7 +170,8 @@
 	icon = 'icons/turf/walls/iron_wall.dmi'
 	icon_state = "iron"
 	sheet_type = /obj/item/stack/rods
-	canSmoothWith = list(/turf/closed/wall/mineral/iron, /obj/structure/falsewall/iron)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_IRON_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_IRON_WALLS)
 
 /turf/closed/wall/mineral/snow
 	name = "packed snow wall"
@@ -187,11 +195,12 @@
 	desc = "A wall with alien alloy plating."
 	icon = 'icons/turf/walls/abductor_wall.dmi'
 	icon_state = "abductor"
-	smoothing_flags = SMOOTH_TRUE|SMOOTH_DIAGONAL
 	sheet_type = /obj/item/stack/sheet/mineral/abductor
 	slicing_duration = 200   //alien wall takes twice as much time to slice
 	explosion_block = 3
-	canSmoothWith = list(/turf/closed/wall/mineral/abductor, /obj/structure/falsewall/abductor)
+	smoothing_flags = SMOOTH_CORNERS|SMOOTH_DIAGONAL
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_ABDUCTOR_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_ABDUCTOR_WALLS)
 
 /////////////////////Titanium walls/////////////////////
 
@@ -204,14 +213,15 @@
 	flags_1 = CAN_BE_DIRTY_1
 	flags_ricochet = RICOCHET_SHINY | RICOCHET_HARD
 	sheet_type = /obj/item/stack/sheet/mineral/titanium
-	smoothing_flags = SMOOTH_MORE|SMOOTH_DIAGONAL
-	canSmoothWith = list(/turf/closed/wall/mineral/titanium, /obj/machinery/door/airlock/shuttle, /obj/machinery/door/airlock, /obj/structure/window/shuttle, /obj/structure/shuttle/engine/heater, /obj/structure/falsewall/titanium)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_DIAGONAL
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_TITANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_TITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /turf/closed/wall/mineral/titanium/rust_heretic_act()
 	return // titanium does not rust
 
 /turf/closed/wall/mineral/titanium/nodiagonal
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
 	icon_state = "map-shuttle_nd"
 
 /turf/closed/wall/mineral/titanium/nosmooth
@@ -251,14 +261,15 @@
 	desc = "An easily-compressable wall used for temporary shelter."
 	icon = 'icons/turf/walls/survival_pod_walls.dmi'
 	icon_state = "smooth"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_DIAGONAL
-	canSmoothWith = list(/turf/closed/wall/mineral/titanium/survival, /obj/machinery/door/airlock, /obj/structure/window/fulltile, /obj/structure/window/reinforced/fulltile, /obj/structure/window/reinforced/tinted/fulltile, /obj/structure/window/shuttle, /obj/structure/shuttle/engine)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_DIAGONAL
+	canSmoothWith = list(SMOOTH_GROUP_TITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_WINDOW_FULLTILE, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /turf/closed/wall/mineral/titanium/survival/nodiagonal
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
 
 /turf/closed/wall/mineral/titanium/survival/pod
-	canSmoothWith = list(/turf/closed/wall/mineral/titanium/survival, /obj/machinery/door/airlock/survival_pod, /obj/structure/window/shuttle/survival_pod)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_TITANIUM_WALLS, SMOOTH_GROUP_SURVIVAL_TIANIUM_POD)
+	canSmoothWith = list(SMOOTH_GROUP_SURVIVAL_TIANIUM_POD)
 
 /////////////////////Plastitanium walls/////////////////////
 
@@ -269,14 +280,15 @@
 	icon_state = "map-shuttle"
 	explosion_block = 4
 	sheet_type = /obj/item/stack/sheet/mineral/plastitanium
-	smoothing_flags = SMOOTH_MORE|SMOOTH_DIAGONAL
-	canSmoothWith = list(/turf/closed/wall/mineral/plastitanium, /obj/machinery/door/airlock/shuttle, /obj/machinery/door/airlock, /obj/structure/window/plasma/reinforced/plastitanium, /obj/structure/shuttle/engine, /obj/structure/falsewall/plastitanium)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_DIAGONAL
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_PLASTITANIUM_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_PLASTITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /turf/closed/wall/mineral/plastitanium/rust_heretic_act()
 	return // plastitanium does not rust
 
 /turf/closed/wall/mineral/plastitanium/nodiagonal
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
 	icon_state = "map-shuttle_nd"
 
 /turf/closed/wall/mineral/plastitanium/nosmooth

code/game/turfs/closed/wall/misc_walls.dm

@@ -3,8 +3,8 @@
 	desc = "A cold metal wall engraved with indecipherable symbols. Studying them causes your head to pound."
 	icon = 'icons/turf/walls/cult_wall.dmi'
 	icon_state = "cult"
+	smoothing_flags = SMOOTH_CORNERS
 	canSmoothWith = null
-	smoothing_flags = SMOOTH_MORE
 	sheet_type = /obj/item/stack/sheet/runed_metal
 	sheet_amount = 1
 	girder_type = /obj/structure/girder/cult

code/game/turfs/closed/wall/reinf_walls.dm

@@ -199,7 +199,7 @@
 		smoothing_flags = NONE
 		clear_smooth_overlays()
 	else
-		smoothing_flags = SMOOTH_TRUE
+		smoothing_flags = SMOOTH_CORNERS
 		QUEUE_SMOOTH_NEIGHBORS(src)
 		QUEUE_SMOOTH(src)
 
@@ -237,14 +237,15 @@
 	icon_state = "map-shuttle"
 	explosion_block = 20
 	sheet_type = /obj/item/stack/sheet/mineral/plastitanium
-	smoothing_flags = SMOOTH_MORE|SMOOTH_DIAGONAL
-	canSmoothWith = list(/turf/closed/wall/r_wall/syndicate, /turf/closed/wall/mineral/plastitanium, /obj/machinery/door/airlock/shuttle, /obj/machinery/door/airlock, /obj/structure/window/plasma/reinforced/plastitanium, /obj/structure/shuttle/engine, /obj/structure/falsewall/plastitanium)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_DIAGONAL
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS, SMOOTH_GROUP_SYNDICATE_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_SYNDICATE_WALLS, SMOOTH_GROUP_PLASTITANIUM_WALLS, SMOOTH_GROUP_AIRLOCK, SMOOTH_GROUP_SHUTTLE_PARTS)
 
 /turf/closed/wall/r_wall/syndicate/rcd_vals(mob/user, obj/item/construction/rcd/the_rcd)
 	return FALSE
 
 /turf/closed/wall/r_wall/syndicate/nodiagonal
-	smoothing_flags = SMOOTH_MORE
+	smoothing_flags = SMOOTH_CORNERS
 	icon_state = "map-shuttle_nd"
 
 /turf/closed/wall/r_wall/syndicate/nosmooth

code/game/turfs/closed/walls.dm

@@ -14,6 +14,10 @@
 
 	flags_ricochet = RICOCHET_HARD
 
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_WALLS)
+
 	///lower numbers are harder. Used to determine the probability of a hulk smashing through.
 	var/hardness = 40
 	var/slicing_duration = 100  //default time taken to slice the wall
@@ -21,15 +25,6 @@
 	var/sheet_amount = 2
 	var/girder_type = /obj/structure/girder
 
-	canSmoothWith = list(
-	/turf/closed/wall,
-	/turf/closed/wall/r_wall,
-	/obj/structure/falsewall,
-	/obj/structure/falsewall/reinforced,
-	/turf/closed/wall/rust,
-	/turf/closed/wall/r_wall/rust)
-	smoothing_flags = SMOOTH_TRUE
-
 	var/list/dent_decals
 
 /turf/closed/wall/Initialize(mapload)

code/game/turfs/open/_open.dm

@@ -122,7 +122,7 @@
 	icon = 'icons/turf/floors/hierophant_floor.dmi'
 	initial_gas_mix = LAVALAND_DEFAULT_ATMOS
 	baseturfs = /turf/open/indestructible/hierophant
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 	tiled_dirt = FALSE
 
 /turf/open/indestructible/hierophant/two

code/game/turfs/open/chasm.dm

@@ -3,10 +3,11 @@
 	name = "chasm"
 	desc = "Watch your step."
 	baseturfs = /turf/open/chasm
-	smoothing_flags = SMOOTH_TRUE | SMOOTH_BORDER | SMOOTH_MORE
 	icon = 'icons/turf/floors/chasms.dmi'
 	icon_state = "smooth"
-	canSmoothWith = list(/turf/open/floor/fakepit, /turf/open/chasm)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_TURF_CHASM)
+	canSmoothWith = list(SMOOTH_GROUP_TURF_CHASM)
 	density = TRUE //This will prevent hostile mobs from pathing into chasms, while the canpass override will still let it function like an open turf
 	bullet_bounce_sound = null //abandon all hope ye who enter
 

code/game/turfs/open/floor/fancy_floor.dm

@@ -176,8 +176,9 @@
 	icon_state = "carpet"
 	floor_tile = /obj/item/stack/tile/carpet
 	broken_states = list("damaged")
-	smoothing_flags = SMOOTH_TRUE
-	canSmoothWith = list(/turf/open/floor/carpet, /turf/open/floor/carpet/airless)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET)
 	flags_1 = NONE
 	bullet_bounce_sound = null
 	footstep = FOOTSTEP_CARPET
@@ -208,47 +209,56 @@
 /turf/open/floor/carpet/black
 	icon = 'icons/turf/floors/carpet_black.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/black
-	canSmoothWith = list(/turf/open/floor/carpet/black, /turf/open/floor/carpet/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_BLACK)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_BLACK)
 
 /turf/open/floor/carpet/blue
 	icon = 'icons/turf/floors/carpet_blue.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/blue
-	canSmoothWith = list(/turf/open/floor/carpet/blue, /turf/open/floor/carpet/blue/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_BLUE)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_BLUE)
 
 /turf/open/floor/carpet/cyan
 	icon = 'icons/turf/floors/carpet_cyan.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/cyan
-	canSmoothWith = list(/turf/open/floor/carpet/cyan, /turf/open/floor/carpet/cyan/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_CYAN)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_CYAN)
 
 /turf/open/floor/carpet/green
 	icon = 'icons/turf/floors/carpet_green.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/green
-	canSmoothWith = list(/turf/open/floor/carpet/green, /turf/open/floor/carpet/green/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_GREEN)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_GREEN)
 
 /turf/open/floor/carpet/orange
 	icon = 'icons/turf/floors/carpet_orange.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/orange
-	canSmoothWith = list(/turf/open/floor/carpet/orange, /turf/open/floor/carpet/orange/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_ORANGE)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_ORANGE)
 
 /turf/open/floor/carpet/purple
 	icon = 'icons/turf/floors/carpet_purple.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/purple
-	canSmoothWith = list(/turf/open/floor/carpet/purple, /turf/open/floor/carpet/purple/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_PURPLE)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_PURPLE)
 
 /turf/open/floor/carpet/red
 	icon = 'icons/turf/floors/carpet_red.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/red
-	canSmoothWith = list(/turf/open/floor/carpet/red, /turf/open/floor/carpet/red/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_RED)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_RED)
 
 /turf/open/floor/carpet/royalblack
 	icon = 'icons/turf/floors/carpet_royalblack.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/royalblack
-	canSmoothWith = list(/turf/open/floor/carpet/royalblack, /turf/open/floor/carpet/royalblack/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_ROYAL_BLACK)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_ROYAL_BLACK)
 
 /turf/open/floor/carpet/royalblue
 	icon = 'icons/turf/floors/carpet_royalblue.dmi'
 	floor_tile = /obj/item/stack/tile/carpet/royalblue
-	canSmoothWith = list(/turf/open/floor/carpet/royalblue, /turf/open/floor/carpet/royalblue/airless)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_CARPET_ROYAL_BLUE)
+	canSmoothWith = list(SMOOTH_GROUP_CARPET_ROYAL_BLUE)
 
 //*****Airless versions of all of the above.*****
 /turf/open/floor/carpet/airless
@@ -304,8 +314,9 @@
 
 /turf/open/floor/fakepit
 	desc = "A clever illusion designed to look like a bottomless pit."
-	smoothing_flags = SMOOTH_TRUE | SMOOTH_BORDER | SMOOTH_MORE
-	canSmoothWith = list(/turf/open/floor/fakepit)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_TURF_CHASM)
+	canSmoothWith = list(SMOOTH_GROUP_TURF_CHASM)
 	icon = 'icons/turf/floors/Chasms.dmi'
 	icon_state = "smooth"
 	tiled_dirt = FALSE

code/game/turfs/open/floor/plating/misc_plating.dm

@@ -47,7 +47,7 @@
 	gender = PLURAL
 	name = "ash"
 	icon_state = "ash"
-	smoothing_flags = SMOOTH_MORE|SMOOTH_BORDER
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
 	var/smooth_icon = 'icons/turf/floors/ash.dmi'
 	desc = "The ground is covered in volcanic ash."
 	baseturfs = /turf/open/floor/plating/ashplanet/wateryrock //I assume this will be a chasm eventually, once this becomes an actual surface
@@ -78,7 +78,8 @@
 	return
 
 /turf/open/floor/plating/ashplanet/ash
-	canSmoothWith = list(/turf/open/floor/plating/ashplanet/ash, /turf/closed)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_ASH)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_ASH, SMOOTH_GROUP_CLOSED_TURFS)
 	layer = HIGH_TURF_LAYER
 	slowdown = 1
 
@@ -88,7 +89,8 @@
 	icon_state = "rockyash"
 	smooth_icon = 'icons/turf/floors/rocky_ash.dmi'
 	layer = MID_TURF_LAYER
-	canSmoothWith = list(/turf/open/floor/plating/ashplanet/rocky, /turf/closed)
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_ASH_ROCKY)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_ASH_ROCKY, SMOOTH_GROUP_CLOSED_TURFS)
 	footstep = FOOTSTEP_FLOOR
 	barefootstep = FOOTSTEP_HARD_BAREFOOT
 	clawfootstep = FOOTSTEP_HARD_CLAW
@@ -209,8 +211,9 @@
 
 /turf/open/floor/plating/ice/smooth
 	icon_state = "smooth"
-	smoothing_flags = SMOOTH_MORE | SMOOTH_BORDER
-	canSmoothWith = list(/turf/open/floor/plating/ice/smooth, /turf/open/floor/plating/ice, /turf/open/floor/plating/ice/colder)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_ICE)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_ICE)
 
 /turf/open/floor/plating/ice/colder
 	temperature = 140
@@ -249,8 +252,9 @@
 	initial_gas_mix = ICEMOON_DEFAULT_ATMOS
 
 /turf/open/floor/plating/snowed/smoothed
-	smoothing_flags = SMOOTH_MORE | SMOOTH_BORDER
-	canSmoothWith = list(/turf/open/floor/plating/snowed/smoothed, /turf/open/floor/plating/snowed)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_SNOWED)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_SNOWED)
 	planetary_atmos = TRUE
 	icon = 'icons/turf/floors/snow_turf.dmi'
 	icon_state = "smooth"

code/game/turfs/open/lava.dm

@@ -182,8 +182,9 @@
 	baseturfs = /turf/open/lava/smooth
 	icon = 'icons/turf/floors/lava.dmi'
 	icon_state = "unsmooth"
-	smoothing_flags = SMOOTH_MORE | SMOOTH_BORDER
-	canSmoothWith = list(/turf/open/lava/smooth)
+	smoothing_flags = SMOOTH_CORNERS | SMOOTH_BORDER
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_LAVA)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_LAVA)
 
 /turf/open/lava/smooth/lava_land_surface
 	initial_gas_mix = LAVALAND_DEFAULT_ATMOS

code/game/turfs/open/space/space.dm

@@ -41,6 +41,15 @@
 		stack_trace("Warning: [src]([type]) initialized multiple times!")
 	flags_1 |= INITIALIZED_1
 
+	if (length(smoothing_groups))
+		sortTim(smoothing_groups) //In case it's not properly ordered, let's avoid duplicate entries with the same values.
+		SET_BITFLAG_LIST(smoothing_groups)
+	if (length(canSmoothWith))
+		sortTim(canSmoothWith)
+		if(canSmoothWith[length(canSmoothWith)] > MAX_S_TURF) //If the last element is higher than the maximum turf-only value, then it must scan turf contents for smoothing targets.
+			smoothing_flags |= SMOOTH_OBJ
+		SET_BITFLAG_LIST(canSmoothWith)
+
 	var/area/A = loc
 	if(!IS_DYNAMIC_LIGHTING(src) && IS_DYNAMIC_LIGHTING(A))
 		add_overlay(/obj/effect/fullbright)

code/game/turfs/open/transparent.dm

@@ -56,8 +56,9 @@
 	desc = "Dont jump on it, or do, I'm not your mom."
 	icon = 'icons/turf/floors/glass.dmi'
 	icon_state = "floor_glass"
-	smoothing_flags = SMOOTH_MORE
-	canSmoothWith = list(/turf/open/transparent/glass, /turf/open/transparent/glass/reinforced)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_TURF_OPEN, SMOOTH_GROUP_FLOOR_TRANSPARENT_GLASS)
+	canSmoothWith = list(SMOOTH_GROUP_FLOOR_TRANSPARENT_GLASS)
 	footstep = FOOTSTEP_PLATING
 	barefootstep = FOOTSTEP_HARD_BAREFOOT
 	clawfootstep = FOOTSTEP_HARD_CLAW

code/game/turfs/turf.dm

@@ -61,8 +61,18 @@ GLOBAL_LIST_EMPTY(station_turfs)
 	assemble_baseturfs()
 
 	levelupdate()
-	if(smoothing_flags)
+
+	if (length(smoothing_groups))
+		sortTim(smoothing_groups) //In case it's not properly ordered, let's avoid duplicate entries with the same values.
+		SET_BITFLAG_LIST(smoothing_groups)
+	if (length(canSmoothWith))
+		sortTim(canSmoothWith)
+		if(canSmoothWith[length(canSmoothWith)] > MAX_S_TURF) //If the last element is higher than the maximum turf-only value, then it must scan turf contents for smoothing targets.
+			smoothing_flags |= SMOOTH_OBJ
+		SET_BITFLAG_LIST(canSmoothWith)
+	if (smoothing_flags)
 		QUEUE_SMOOTH(src)
+
 	visibilityChanged()
 
 	for(var/atom/movable/AM in src)

code/modules/holodeck/turfs.dm

@@ -105,7 +105,7 @@
 	icon = 'icons/turf/floors/carpet.dmi'
 	icon_state = "carpet"
 	floor_tile = /obj/item/stack/tile/carpet
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 	canSmoothWith = null
 	bullet_bounce_sound = null
 	tiled_dirt = FALSE

code/modules/mining/equipment/survival_pod.dm

@@ -87,8 +87,9 @@
 	name = "pod window"
 	icon = 'icons/obj/smooth_structures/pod_window.dmi'
 	icon_state = "smooth"
-	smoothing_flags = SMOOTH_MORE
-	canSmoothWith = list(/turf/closed/wall/mineral/titanium/survival, /obj/machinery/door/airlock/survival_pod, /obj/structure/window/shuttle/survival_pod)
+	smoothing_flags = SMOOTH_CORNERS
+	smoothing_groups = list(SMOOTH_GROUP_SHUTTLE_PARTS, SMOOTH_GROUP_SURVIVAL_TIANIUM_POD)
+	canSmoothWith = list(SMOOTH_GROUP_SURVIVAL_TIANIUM_POD)
 
 /obj/structure/window/shuttle/survival_pod/spawner/north
 	dir = NORTH

code/modules/mob/living/simple_animal/hostile/megafauna/hierophant.dm

@@ -519,7 +519,7 @@ Difficulty: Hard
 	icon_state = "wall"
 	light_range = MINIMUM_USEFUL_LIGHT_RANGE
 	duration = 100
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 
 /obj/effect/temp_visual/hierophant/wall/Initialize(mapload, new_caster)
 	. = ..()

code/modules/mob/living/simple_animal/hostile/mining_mobs/elites/elite.dm

@@ -304,7 +304,7 @@ While using this makes the system rely on OnFire, it still gives options for tim
 	icon = 'icons/turf/walls/hierophant_wall_temp.dmi'
 	icon_state = "wall"
 	duration = 50
-	smoothing_flags = SMOOTH_TRUE
+	smoothing_flags = SMOOTH_CORNERS
 	layer = BELOW_MOB_LAYER
 	color = rgb(255,0,0)
 	light_range = MINIMUM_USEFUL_LIGHT_RANGE

code/modules/mob/living/simple_animal/hostile/venus_human_trap.dm

@@ -14,11 +14,11 @@
 	icon = 'icons/effects/spacevines.dmi'
 	icon_state = "flower_bud"
 	layer = SPACEVINE_MOB_LAYER
-	opacity = 0
-	canSmoothWith = list()
+	opacity = FALSE
+	canSmoothWith = null
 	smoothing_flags = NONE
-	/// The amount of time it takes to create a venus human trap, in deciseconds
-	var/growth_time = 1200
+	/// The amount of time it takes to create a venus human trap.
+	var/growth_time = 120 SECONDS
 
 /obj/structure/alien/resin/flower_bud_enemy/Initialize()
 	. = ..()

code/modules/ruins/spaceruin_code/hilbertshotel.dm

@@ -198,7 +198,8 @@ GLOBAL_VAR_INIT(hhmysteryRoomNumber, 1337)
 	name = "hotel wall"
 	desc = "A wall designed to protect the security of the hotel's guests."
 	icon_state = "hotelwall"
-	canSmoothWith = list(/turf/closed/indestructible/hotelwall)
+	smoothing_groups = list(SMOOTH_GROUP_CLOSED_TURFS, SMOOTH_GROUP_HOTEL_WALLS)
+	canSmoothWith = list(SMOOTH_GROUP_HOTEL_WALLS)
 	explosion_block = INFINITY
 
 /turf/open/indestructible/hotelwood

tgstation.dme

@@ -53,6 +53,7 @@
 #include "code\__DEFINES\footsteps.dm"
 #include "code\__DEFINES\forensics.dm"
 #include "code\__DEFINES\hud.dm"
+#include "code\__DEFINES\icon_smoothing.dm"
 #include "code\__DEFINES\interaction_flags.dm"
 #include "code\__DEFINES\inventory.dm"
 #include "code\__DEFINES\is_helpers.dm"
@@ -127,6 +128,7 @@
 #include "code\__HELPERS\_string_lists.dm"
 #include "code\__HELPERS\areas.dm"
 #include "code\__HELPERS\AStar.dm"
+#include "code\__HELPERS\bitflag_lists.dm"
 #include "code\__HELPERS\chat.dm"
 #include "code\__HELPERS\cmp.dm"
 #include "code\__HELPERS\config.dm"