General Lighting Improvements (#3482)

changes:

Z-lights can now shine both upwards and downwards.
Z-lights will now get less intense with each zlevel traversed.
Sunlight no longer has distance falloff.
Minor optimizations/simplification for directional lighting.

code/modules/lighting/lighting_source.dm

@@ -34,7 +34,6 @@
 	var/tmp/cached_origin_x // The last known X coord of the origin.
 	var/tmp/cached_origin_y // The last known Y coord of the origin.
 	var/tmp/old_direction   // The last known direction of the origin.
-	var/tmp/targ_sign       // The sign to test the point against.
 	var/tmp/test_x_offset   // How much the X coord should be offset due to direction.
 	var/tmp/test_y_offset   // How much the Y coord should be offset due to direction.
 	var/tmp/facing_opaque = FALSE
@@ -46,6 +45,8 @@
 
 	var/needs_update = LIGHTING_NO_UPDATE
 
+	var/skip_falloff = FALSE	// ONLY for use with sunlight, behavior is undefined if TRUE on regular sources.
+
 /datum/light_source/New(atom/owner, atom/top)
 	source_atom = owner // Set our new owner.
 
@@ -68,8 +69,6 @@
 
 	//L_PROF(source_atom, "source_new([type])")
 
-	return ..()
-
 // Kill ourselves.
 /datum/light_source/Destroy(force)
 	//L_PROF(source_atom, "source_destroy")
@@ -159,31 +158,19 @@
 #define MINMAX(NUM) ((NUM) < 0 ? -round(-(NUM)) : round(NUM))
 #define ARBITRARY_NUMBER 10
 
-/datum/light_source/proc/update_angle()
-	var/turf/T = get_turf(top_atom)
-
-	var/ndir
-	if (istype(top_atom, /mob) && top_atom:facing_dir)
-		ndir = top_atom:facing_dir
-	else
-		ndir = top_atom.dir
-
-	// Don't do anything if nothing is different, trig ain't free.
-	if (T.x == cached_origin_x && T.y == cached_origin_y && old_direction == ndir)
-		return
-
+/datum/light_source/proc/regenerate_angle(ndir)
 	old_direction = ndir
 
-	var/turf/front = get_step(T, old_direction)
+	var/turf/front = get_step(source_turf, old_direction)
 	facing_opaque = (front && front.has_opaque_atom)
 
-	cached_origin_x = test_x_offset = T.x
-	cached_origin_y = test_y_offset = T.y
+	cached_origin_x = test_x_offset = source_turf.x
+	cached_origin_y = test_y_offset = source_turf.y
 
 	if (facing_opaque)
 		return
 
-	var/angle = light_angle / 2
+	var/angle = light_angle * 0.5
 	switch (old_direction)
 		if (NORTH)
 			limit_a_t = angle + 90
@@ -214,8 +201,6 @@
 	limit_b_x = MINMAX(limit_b_x)
 	limit_b_y = POLAR_TO_CART_Y(light_range + ARBITRARY_NUMBER, limit_b_t)
 	limit_b_y = MINMAX(limit_b_y)
-	// This won't change unless the origin or dir changes, might as well do it here.
-	targ_sign = PSEUDO_WEDGE(limit_a_x, limit_a_y, limit_b_x, limit_b_y) > 0
 
 #undef ARBITRARY_NUMBER
 #undef POLAR_TO_CART_X
@@ -248,7 +233,16 @@
 
 	var/actual_range = light_range
 
-	APPLY_CORNER(C,now)
+	var/Sx = source_turf.x
+	var/Sy = source_turf.y
+	var/Sz = source_turf.z
+
+	if (skip_falloff)
+		APPLY_CORNER_SIMPLE(C)
+	else
+		var/height = C.z == Sz ? LIGHTING_HEIGHT : CALCULATE_CORNER_HEIGHT(C.z, Sz)
+		APPLY_CORNER(C, now, Sx, Sy, height)
+
 	UNSETEMPTY(effect_str)
 
 // If you update this, update the equivalent proc in lighting_source_novis.dm.
@@ -305,11 +299,36 @@
 		light_angle = source_atom.light_wedge
 		update = TRUE
 
-	if (light_angle && top_atom.dir != old_direction)
-		update = TRUE
+	if (light_angle)
+		var/ndir
+		if (istype(top_atom, /mob) && top_atom:facing_dir)
+			ndir = top_atom:facing_dir
+		else
+			ndir = top_atom.dir
 
-	if (update && light_angle)
-		update_angle()
+		if (old_direction != ndir)	// If our direction has changed, we need to regenerate all the angle info.
+			regenerate_angle(ndir)
+			update = TRUE
+		else // Check if it was just a x/y translation, and update our vars without an regenerate_angle() call if it is.
+			var/co_updated = FALSE
+			if (source_turf.x != cached_origin_x)
+				test_x_offset += source_turf.x - cached_origin_x
+				cached_origin_x = source_turf.x
+
+				co_updated = TRUE
+
+			if (source_turf.y != cached_origin_y)
+				test_y_offset += source_turf.y - cached_origin_y
+				cached_origin_y = source_turf.y
+
+				co_updated = TRUE
+
+			if (co_updated)
+				// We might be facing a wall now.
+				var/turf/front = get_step(source_turf, old_direction)
+				facing_opaque = (front && front.has_opaque_atom)
+
+				update = TRUE
 
 	if (update)
 		needs_update = LIGHTING_CHECK_UPDATE
@@ -324,11 +343,18 @@
 	var/list/Tcorners
 	var/Sx = source_turf.x
 	var/Sy = source_turf.y
+	var/Sz = source_turf.z
+	var/corner_height = LIGHTING_HEIGHT
 	var/actual_range = (light_angle && facing_opaque) ? light_range * LIGHTING_BLOCKED_FACTOR : light_range
 	var/test_x
 	var/test_y
 
-	FOR_DVIEW(T, Ceiling(actual_range), source_turf, 0)
+	var/zlights_going_up = FALSE
+	var/turf/originalT	// This is needed to reset our search point for bidirectional Z-lights.
+
+	FOR_DVIEW(originalT, Ceiling(actual_range), source_turf, 0)
+		T = originalT
+		zlights_going_up = FALSE
 		check_t:
 
 		if (light_angle && !facing_opaque)	// Directional lighting coordinate filter.
@@ -336,7 +362,7 @@
 			test_y = T.y - test_y_offset
 
 			// if the signs of both of these are NOT the same, the point is NOT within the cone.
-			if (((PSEUDO_WEDGE(limit_a_x, limit_a_y, test_x, test_y) > 0) != targ_sign) || ((PSEUDO_WEDGE(test_x, test_y, limit_b_x, limit_b_y) > 0) != targ_sign))
+			if ((PSEUDO_WEDGE(limit_a_x, limit_a_y, test_x, test_y) > 0) || (PSEUDO_WEDGE(test_x, test_y, limit_b_x, limit_b_y) > 0))
 				continue
 
 		if (T.dynamic_lighting || T.light_sources)
@@ -362,9 +388,21 @@
 
 		turfs += T
 
-		if (isopenturf(T) && T:below)
-			T = T:below	// Consider the turf below us as well. (Z-lights)
-			goto check_t
+		// Note: above is defined on ALL turfs, but below is only defined on OPEN TURFS.
+
+		zlight_check:
+		if (zlights_going_up)	// If we're searching upwards, check above.
+			if (istype(T.above))	// We escape the goto loop if this condition is false.
+				T = T.above
+				goto check_t
+		else
+			if (isopenturf(T) && T:below)	// Not searching upwards and we have a below turf.
+				T = T:below	// Consider the turf below us as well. (Z-lights)
+				goto check_t
+			else // Not searching upwards and we don't have a below turf.
+				zlights_going_up = TRUE
+				T = originalT
+				goto zlight_check
 
 	END_FOR_DVIEW
 
@@ -391,7 +429,7 @@
 				effect_str[C] = 0
 				continue
 
-			APPLY_CORNER_XY(C, now, Sx, Sy)
+			APPLY_CORNER_BY_HEIGHT(now)
 	else
 		L = corners - effect_str
 		for (thing in L)
@@ -401,7 +439,7 @@
 				effect_str[C] = 0
 				continue
 
-			APPLY_CORNER_XY(C, now, Sx, Sy)
+			APPLY_CORNER_BY_HEIGHT(now)
 
 		for (thing in corners - L)
 			C = thing
@@ -409,7 +447,7 @@
 				effect_str[C] = 0
 				continue
 
-			APPLY_CORNER_XY(C, now, Sx, Sy)
+			APPLY_CORNER_BY_HEIGHT(now)
 
 	L = effect_str - corners
 	for (thing in L)