Ambient Occlusion (#3419)

Adds an implementation of Europa's wall ambient occlusion, extended to operate on openturfs as well.

code/modules/lighting/lighting_atom.dm

@@ -104,6 +104,9 @@
 	if (new_opacity == TRUE)
 		T.has_opaque_atom = TRUE
 		T.reconsider_lights()
+#ifdef AO_USE_LIGHTING_OPACITY
+		T.regenerate_ao()
+#endif
 	else
 		var/old_has_opaque_atom = T.has_opaque_atom
 		T.recalc_atom_opacity()

code/modules/lighting/lighting_turf.dm

@@ -119,20 +119,38 @@
 
 // Can't think of a good name, this proc will recalculate the has_opaque_atom variable.
 /turf/proc/recalc_atom_opacity()
+#ifdef AO_USE_LIGHTING_OPACITY
+	var/old = has_opaque_atom
+#endif
+
 	has_opaque_atom = FALSE
-	for (var/atom/A in src.contents + src) // Loop through every movable atom on our tile PLUS ourselves (we matter too...)
-		if (A.opacity)
-			has_opaque_atom = TRUE
-			return 	// No need to continue if we find something opaque.
+	if (opacity)
+		has_opaque_atom = TRUE
+	else
+		for (var/thing in src) // Loop through every movable atom on our tile
+			var/atom/movable/A = thing
+			if (A.opacity)
+				has_opaque_atom = TRUE
+				break 	// No need to continue if we find something opaque.
+
+#ifdef AO_USE_LIGHTING_OPACITY
+	if (old != has_opaque_atom)
+		queue_ao()
+#endif
 
 // If an opaque movable atom moves around we need to potentially update visibility.
 /turf/Entered(atom/movable/Obj, atom/OldLoc)
 	. = ..()
 
-	if (Obj && Obj.opacity)
+	if (Obj && Obj.opacity && !has_opaque_atom)
 		has_opaque_atom = TRUE // Make sure to do this before reconsider_lights(), incase we're on instant updates. Guaranteed to be on in this case.
 		reconsider_lights()
 
+#ifdef AO_USE_LIGHTING_OPACITY
+		// Hook for AO.
+		regenerate_ao()
+#endif
+
 /turf/Exited(atom/movable/Obj, atom/newloc)
 	. = ..()
 
@@ -187,9 +205,12 @@
 	var/list/old_affecting_lights = affecting_lights
 	var/old_lighting_overlay = lighting_overlay
 	var/list/old_corners = corners
+	var/old_ao_neighbors = ao_neighbors
 
 	. = ..()
 
+	ao_neighbors = old_ao_neighbors
+
 	recalc_atom_opacity()
 	lighting_overlay = old_lighting_overlay
 	if (lighting_overlay && lighting_overlay.loc != src)