(svn r25998) -Document [FS#5661]: why catchment area's are (slightly) inconsistent

1 files changed, 31 insertions, 0 deletions

diff --git a/known-bugs.txt b/known-bugs.txt
index 00025a63f..a8591e965 100644
--- a/known-bugs.txt
+++ b/known-bugs.txt
@@ -403,3 +403,34 @@ Mouse cursor going missing with SDL [FS#4997]:
 	We cannot fix this problem as SDL simply does not provide the
 	required information in these corner cases. This is a bug in SDL
 	and as such there is little that we can do about it.
+
+Inconsistent catchment areas [FS#5661]:
+	Due to performance decisions the catchment area for cargo accepted
+	by a station for delivery to houses or industries differs from the
+	catchment area for cargo that is delivered to stations from houses
+	or industries.
+
+	Conceptually they work the same, but the effect in game differs.
+	They work by finding the closest destination "around" the source
+	which is within a certain distance. This distance depends on the
+	type of station, e.g. road stops have a smaller catchment area than
+	large airports. In both cases the bounding box, the smallest
+	rectangle that contains all tiles of something, is searched for the
+	target of the cargo, and then spiraling outwards finding the closest
+	tile of the target.
+
+	In the case of a station with two tiles spread far apart with a house
+	that is within the station's bounding box, it would be possible that
+	the spiraling search from the house does not reach one of the station
+	tiles before the search ends, i.e. all tiles within that distance
+	are searched. So the house does not deliver cargo to the station. On
+	the other hand, the station will deliver cargo because the house
+	falls within the bounding box, and thus search area.
+
+	It is possible to make these consistent, but then cargo from a house
+	to a station needs to search up to 32 tiles around itself, i.e. 64
+	by 64 tiles, to find all possible stations it could deliver to
+	instead of 10 by 10 tiles (40 times more tiles). Alternatively the
+	search from a station could be changed to use the actual tiles, but
+	that would require considering checking 10 by 10 tiles for each of
+	the tiles of a station, instead of just once.