If I remember correctly*, you can only specify the cost on an edge--not a node. Keep in mind you can't customize costs using the auto graph feature. Using auto graph, the cost to move in a cardinal direction is 1, and the cost to move diagonal is 1.414. If you want to customize costs, you'll have to create the graph manually using the 'create note' and 'create connection' blocks. AITools uses directed graphs, so be sure to set up the connection both ways i.e. node A connects to B and node B connects to A. (Although you can use one-way connections for cliffs, river currents, etc., and the A* implementation will know what to do with it)
There are a couple different ways set this up for your purposes. You could set the cost of an edge leading into a tile to be the cost of the tile itself. (Example: Consider a grass tile and mountain tile next to each other. It costs 2.5 AP to move onto the mountain tile, and 1 AP to move into the grass tile). Or, to get an undirected graph version, just set the cost both ways to the average cost of each tile.
Setting the cost of a tile is a good idea. Here's one approach you can use.
make a new graph
// Setting up the nodes
for each row r
for each column c
if a tile exists at r, c, then
create a node at r, c
end if
end for
end for
// Setting up the connections
for each row r in 0...scene height (in tiles)
for each column c in 0...scene width (in tiles)
if a tile doesn't exist at (r,c) then continue
if a tile exists at (r-1,c) then
set 'cost' to cost of tile at (r-1,c) (pulled from your tile data)
create a connection from node r,c to node r-1,c with cost 'cost'
end if
if a tile exists at (r+1,c) then
set 'cost' to cost of tile at (r+1,c) (pulled from your tile data)
create a connection from node r,c to node r+1,c with cost 'cost'
end if
if a tile exists at (r,c-1) then
set 'cost' to cost of tile at (r,c-1) (pulled from your tile data)
create a connection from node r,c to node r,c-1 with cost 'cost'
end if
if a tile exists at (r,c+1) then
set 'cost' to cost of tile at (r,c+1) (pulled from your tile data)
create a connection from node r,c to node r,c+1 with cost 'cost'
end if
end for
end for
You'll have to modify my psuedo code outline to handle things like tiles that can't be walked on... e.g. use " if a tile exists at (r,c) and can be travelled" instead of " if a tile exists at (r,c)".
* I have three different versions of this extension on my computer in various configurations, so I sometimes get them mixed up.
