Greetings all, been awhile and I started back up coding my wargame. I am stuck on something and would appreciate your help if you are willing. I have a data structure for tiles I am using and when declaring an attack from one tile to another I am trying to determine if it is crossing a River. I have established that rivers run along a tile side(s). Example: Tile[x].NorthRiver, Tile[x].EastRiver, Tile[x].SouthRiver, Tile[x].WestRiver all will be 0 if there isnt a river, and 1 if there is. I am struggling to come up with an algorithm to test all possibilities to return true(well River=1 means that yes this unit has to cross a river). Here’s what I have so far but I need to be able to test cases where you are moving say NE. I need to be able to test the square immediately to the N to see if it ALSO has a river on it’s E side as that should also return true. I think what I have works for pure N, S, E, W tests but how to test for that kind of cardinal point cases? I think what I have works for one type of cardinal point test where there is a river to your N AND E but I realized the case above would be missed. This is a real tough one for me, rest of the game…not a problem so far.

The test case also needs to handle checking the sqare to the east and see if that has a N river too.

IE: the following would all return true if moving/attacking NE:

River N AND E

River N but not E AND River N on square to the E

River E but not N AND River E on square to the N

Having a hard time on last 2 cases…

CODE:

local function RiverCrossingCheck(AX, AY, DX, DY)

```
--AX, AY, DX, DY are the tile x and y values(not pixel points) so that is what must be passed to this function
--Determine if the attacker has to cross a river by checking the vector of the attack.
--compare the vector with a test to see if that side has a river
--if that side has a river return true, else false
--NOTE: The map will have to be marked as a river on both sides. IE: if a tile has a river on it's south side then the tile to the immediate south side must be marked with a North river as well...
--attackers riversides
local N = 0
local NW = 0
local NE = 0
local E = 0
local S = 0
local SE = 0
local SW = 0
local W = 0
local River = 0
local AT=0
--Determine the Attackers tile number so you can reference the river properties.
AT = ((AY-1) * MapWidth) + AX;
--ATTACKING NORTH
if (AY-DY = 1) then
N = Tile[AT].NorthSideRiver
end
--ATTACKING EAST
if (AX-DX = -1) then
E = Tile[AT].EastSideRiver
end
--ATTACKING SOUTH
if (AY-DY = -1) then
S = Tile[AT].SouthSideRiver
end
--ATTACKING WEST
if (AX-DX = 1) then
W = Tile[AT].WestSideRiver
end
--Check all 8 cardinal points to find the vector of attack:
--Need to get the riversides on all 8 adjacent squares:
--because if a river is on E but not N AND your attacking NE
--it would have been missed by my initial algorithym because
--if the river in the square to the N also has and E river side that
--should return true..
--
--So 1 algorithm to test pure N, S, E, W
--another for NE, NW, SE, SW is also needed.
if (N==1 ) then
if(E==1) then
River = 1
end
if(W==1) then
River = 1
end
end
```

…

```
return River
```

end