I am experimenting with Apple's GameplayKit, SpriteKit and Swift. I am trying to wrap my head around pathfinding through tiles which are passable from only one side.
The diagram below shows two problems:
On the left is a simple solution, I understand how to move from the green position to the red position as all I need to do is remove the wall nodes (the black outlined squares) from the graph and compute the path.
The right hand side of the diagram is puzzling me. Say I want to have tiles which have a wall along their left hand side (as illustrated in the diagram) but I still want to be able to navigate to a tile with a wall. How do I go about telling the graph that those tiles with walls on the left-hand side of the tile are only passable if approached from the top, bottom or right side and not the left?
In response to Alessandro's comment I will explain about the structure of the code. I'm using the new TileMapNode introduced to SpriteKit in iOS 10 to represent the tile map. Each tile is a SKTileDefinition. Custom properties can be set on SKTileDefinition (for instance I could set an Int to represent if there is a wall on the top, bottom, left or right of the tile). The actual representation of the map is less important than how you path find with GameplayKit. As far as I can see, GameplayKit only allows you to remove nodes from the graph that are impassable but what I want to do I mark some nodes as passable but only from a particular direction.
This strikes me as a common problem (as lots of games don't have to sacrifice an entire tile to represent an internal wall) but I don't have the faintest idea how to go about it.
