Feb22010

map squares are uc santa cruz computer science game

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Unformatted text preview: Science – Game Design A* pathfinding •  A* algorithm is widely used as the conceptual core for pathfinding in computer games –  Most commercial games use variants of the algorithm tailored to the specific game –  Original paper: •  A* is a graph search algorithm •  A Formal Basis for the HeurisDc DeterminaDon of Minimum Cost Paths •  Hart, P.E.; Nilsson, N.J.; Raphael, B. •  IEEE Trans. Systems Science and Cyberne6cs, 4(2), July 1968, pp. 100 ­107 –  There is a large research literature on graph search algorithms, and computer game pathfinding UC Santa Cruz Computer Science – Game Design Overview of A* algorithm •  The following slides borrow heavily from: •  Problem –  A* Pathfinding for Beginners, by Patrick Lester •  hpp://www.policyalmanac.org/games/aStarTutorial.htm –  A unit wants to move from point A to point B on a game map, ideally along the shortest path •  Assume the game map is a rectangular grid –  Makes explanaDon easier, algorithm can accommodate many grid types –  The literature views the map as a graph –  Open/walkable (open terrain) –  Or closed/unwalkable (walls, water, etc.) •  Map squares are UC Santa Cruz Computer Science – Game Design Running Example •  A unit in the green square wants to move to the red square –  From here on out, we’ll call the squares “nodes” to be consistent with the research literature •  Moving •  ObservaDons –  Horizontally or verDcally requires 10 movement points –  Diagonal movement requires 14 movement points –  Cannot move through blue squares (wall, unwalkable) –  Can’t just draw a line between A and B and follow that line –  It’s not ideal to just follow the minimal line between A and B unDl you hit the wall, then walk along wall •  Not an opDmal path •  Wall in ­between Pathfinding example. Green square is starDng locaDon, red square is desired goal. Blue is a wall. Black is walkable, blue is unwalkable. UC Santa Cruz Computer Science – Game Design Open and Closed Lists •  StarDng the search –  Add A to open list of nodes to be consi...
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