Fix ambient occlusion on xeno weeds and wall corners (#37987)

code/__HELPERS/icon_smoothing.dm

@@ -117,7 +117,7 @@
 		return
 	if(QDELETED(A))
 		return
-	if((A.smooth & SMOOTH_TRUE) || (A.smooth & SMOOTH_MORE))
+	if(A.smooth & (SMOOTH_TRUE | SMOOTH_MORE))
 		var/adjacencies = calculate_adjacencies(A)
 
 		if(A.smooth & SMOOTH_DIAGONAL)
@@ -156,7 +156,7 @@
 /turf/closed/wall/diagonal_smooth(adjacencies)
 	adjacencies = reverse_ndir(..())
 	if(adjacencies)
-		var/mutable_appearance/underlay_appearance = mutable_appearance(layer = TURF_LAYER)
+		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"])

code/_globalvars/bitfields.dm

@@ -130,12 +130,19 @@ GLOBAL_LIST_INIT(bitfields, list(
 		"MASKINTERNALS" = MASKINTERNALS,
 		"NOSLIP" = NOSLIP,
 		"THICKMATERIAL" = THICKMATERIAL,
-	),
+		),
 	"tesla_flags" = list(
 		"TESLA_MOB_DAMAGE" = TESLA_MOB_DAMAGE,
 		"TESLA_OBJ_DAMAGE" = TESLA_OBJ_DAMAGE,
 		"TESLA_MOB_STUN" = TESLA_MOB_STUN,
 		"TESLA_ALLOW_DUPLICATES" = TESLA_ALLOW_DUPLICATES,
 		"TESLA_MACHINE_EXPLOSIVE" = TESLA_MACHINE_EXPLOSIVE,
-		)
+		),
+	"smooth" = list(
+		"SMOOTH_TRUE" = SMOOTH_TRUE,
+		"SMOOTH_MORE" = SMOOTH_MORE,
+		"SMOOTH_DIAGONAL" = SMOOTH_DIAGONAL,
+		"SMOOTH_BORDER" = SMOOTH_BORDER,
+		"SMOOTH_QUEUED" = SMOOTH_QUEUED,
+		),
 	))

code/game/objects/structures/aliens.dm

@@ -115,6 +115,7 @@
 	anchored = TRUE
 	density = FALSE
 	layer = TURF_LAYER
+	plane = FLOOR_PLANE
 	icon_state = "weeds"
 	max_integrity = 15
 	canSmoothWith = list(/obj/structure/alien/weeds, /turf/closed/wall)