Categories > Board > rex_slg_movement

Introduction

Get move-able area, or moving path between two chess/tiles on an orthogonal or isometric, or hexagonal board.

Links

• Plugin

• ACE table

• Discussion thread

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Dependence

• rex_board
• rex_ginstgroup plugin

Usage

Prepare

This plugin picks tiles of move-able area or moving path into a group. therefor rex_board and rex_ginstgroup objects should be put into project first.

Get moveable area

Main flow

Flow chart of getting cost

Flow chart of filter function

Get move-able area

• Action:Get moveable area
• Action:Get moveable area by UID

There are 5 parameters in action

• Chess : chess to move.

• Moving points : initial moving point. Chess could move to tiles (i.e move-able tiles) when the remaining moving point is large or equal to 0.

• Moving cost : each tile will consume some cost. This parameter could be a number or a string

  • Number : constant moving cost of each tile

  • String : get cost from cost function. Flow chart of cost function is show above.

    • Cost function is started at Condition:On cost, to get cost of this moving

      • Chess Expression:ChessUID
      • start from tile Expression:StartTileUID at LXYZ (Expression:StartX, Expression:StartY)
      • move from tile Expression:PreTileUID at LXYZ (Expression:PreTileX, Expression:PreTileY, 0) , with accumulation cost: Expression:PreTilePathCost
      • to neighbor tile Expression:TileUID at LXYZ (Expression:TileX, Expression:TileY, 0)

    • Return cost by Action:Set cost

      • value >= 0, or
      • Expression:BLOCKING

• Filter : The result of moving area are UID of tiles by default. Or use a filter function if this parameter is not equal to "", to reset or add picked instances. Flow chart of filter function is shown above.

  • Filter function is started at Condition:On filter

    • Filter each tile Expression:TileUID at LXYZ : (Expression:TileX, Expression:TileY, 0)

  • Add an instance by uid into result group by Action:Append filter result

• Group : put move-able tiles into result group , which is a group in instance group object

Shuffle neighbors

Sample capx If property Shuffle neighbors is set to Yes, the order of visited neighbors will be random, i.e. the order of visited nodes is not the same for each request.

Here is the order of tiles in result group with parameters

• parameter Moving points = 3
• parameter Cost = 1
• property Shuffle neighbors = No

Cache cost

If property Cache cost is set to Yes, Condition:On cost will only be triggered once for each tile in a request.

Get moving path

Main flow

Flow chart of getting cost

Get shortest moving path between source chess to destination chess/tile

• Action:Get moving path
• Action:Get moving path by UID

There are 5 parameters in action

• Chess : source chess.

• Tile/Chess : destination chess/tile.

• Moving points : initial moving point. Chess could move to tiles (i.e move-able tiles) when the remaining moving point is large or equal to 0.

• Moving cost : each tile will consume some cost. This parameter is very similar with parameter Moving cost in Action:Get moveable area.

  • Number : constant moving cost of each tile

  • String : get cost from cost function. Flow chart of cost function is show above.

    • Cost function is started at Condition:On cost, to get cost of this moving

      • Chess Expression:ChessUID
      • start from tile Expression:StartTileUID at LXYZ (Expression:StartX, Expression:StartY)
      • move from tile Expression:PreTileUID at LXYZ (Expression:PreTileX, Expression:PreTileY, 0) , with accumulation cost: Expression:PreTilePathCost
      • to neighbor tile Expression:TileUID at LXYZ (Expression:TileX, Expression:TileY, 0)
      • end at tile Expression:EndTileUID at LXYZ (Expression:EndX, Expression:EndY, 0)

    • Return cost by Action:Set cost

      • value >= 0, or
      • Expression:BLOCKING

• Group : pick a path presented by a sequence of tiles into result group , which is a group in instance group object.

Path mode

Configure property Path mode to get a shorter path or shortest path.

Get shortest path

Set property Path mode to

• Random : picking the shortest path randomly
• Diagonal : picking the shortest path which has the maximum changing of moving direction
• Straight : picking the shortest path which has the minimum changing of moving direction
• Line : picking the shortest path which has the minimum changing of moving angle

Get shorter path

Set property Path mode to A*-,

• A* -line, A* -random : using A* algorithm to find path, this will have the best performance. It is recommended that using these modes only when parameter moving point is set to Expression:INFINITY.

Exact or nearest

Set parameter Exact to nearest to get moving path from start tile to nearest target tile. Get the nearest target tile UID by Expression:NearestTileUID. The result of instance group is empty if Exact is set to "" and no path found from start tile to target tile.

Move chess alone path

Using rex_grid_move behavior to move chess alone path after Action:Get moving path.

1. Pick path into group by Action:Get moving path
2. Call C2 function Move to next tile

Add events of C2 function Move to next tile :

1. Pick next tile by Condition:Pop one instance of Instance group plugin
2. Move to tile by Action:Move to chess of grid move behavior
3. chess has moved to the last tile of the path If picking nothing (system condition:Else)

Add events to move to next tile when reached to target tile by Condition:On hit target position of grid move behavior

1. Call C2 function Move to next tile

Sets propertyForce move toYes in grid move behavior, since the move-able (solid) had been determined by this Action:Get moving path.

Uses Expression: PrivateGroup (Instance group plugin) to pick path into private group of chess instance when picking path of multiple chess.

Use case of filter function and cost function

Sample capx This sample capx shows how to implement the filter function and cost function to get move-able area, moving path, and the enemies in a range.

No overlapped with other chess

Filter tiles which the cell of chess is empty, to exclude the tiles which has been occupied by other chess.

1. If (Expression:TileX, Expression:TileY, 0) is empty (Condition:Is empty of board object) under Condition:On filter

   1. Append tile UID Expression:TileUID by Action:Append filter result

Pick enemies

Append enemy instances which stand on tiles, to pick pick enemies in a range.

1. Pick enemy chess by Condition:Pick chess above tile (board object) under Condition:On filter

   1. Append chess UID by Action:Append filter result

No moving across enemies

Return Expression:BLOCKING if the enemy instance stands on tile under in cost function

1. Pick enemy chess by (Expression:TileX, Expression:TileY, 1) (board object) under Condition:On cost

   1. Return Expression:BLOCKING if true

More samples

• Sternhalma

  • Note that Cache cost is set to No

Wrap

Sample capx Set property Wrap to Yes in board object to wrap the logical boundary. It will also effect the result of picking move-able area and moving path. Chess could move from left boundary to right boundary directly.

Accumulated cost

Get accumulated cost from start tile to a specific chess/tile after Action:Get moveable area or Action:Get moving path by Expression:UID2PathCost (sample capx). Return -1 if this specific chess/tile is not in the last scan of request.

Flood fill

Sample capx Action:Get moveable area uses flood fill to find move-able area by Condition:On cost. This feature also could be used to picking neighbor chess/tile which have the same color.

The steps of picking are -

1. Save target color in variable.

2. Call Action:Get moveable area, sets the parameter of Moving point to 1.

3. In Condition:On cost, pick tile/chess instance by Expression:TileUID or (Expression:TileX, Expression:TileY, 0).

4. Compare the color of picked instance with target color

   • Return cost to 0 by Action:Set cost if the color of picked instance is equal to target color, .
   • Otherwise do nothing, the cost will be Expression:BLOCKING by default.

5. Add the source tile into result group by Action:Add instances of (Instance group plugin) after Action:Get moveable area.

More samples

• Diffusion

Move on tilemap

Sample capx Sets all tiles (LZ=0) by string symbols, and sets the squareTx to align to the tilemap object. Then uses these string symbol tile in input parameter of Action:Get moveable area or Action:Get moving path, it will pick tiles by string symbols. Since the results group are not UID of instance in this case, uses

• Condition:For each UID and Expression:Item to retrieve the string symbol for move-able area, or
• Expression:Pop( group_name , 0) to get string symbol in order for moving path.