evil-inside/src/ei/game/algo/AStarNode2D.java

package ei.game.algo;

import ei.game.algo.AStarNeighbour.Location;

/**
 * 
 * @author <EFBFBD>rni Arent
 *
 */
public class AStarNode2D extends AStarNode {
	protected final static float adjacentCost = 1;
	protected final static float diagonalCost = (float)Math.sqrt(2)*adjacentCost;
	protected final static float tieBreaker = adjacentCost/(1024f/1024f); 
	 
	public enum Heuristic {
		Manhattan,
		Euclidean,
		Diagonal,
		DiagonalWithTieBreaking,
		DiagonalWithTieBreakingCrossProduct,
	}
	
	public static Heuristic heuristic = Heuristic.Euclidean;
	
	protected int x, y;
	
	public AStarNode2D(int x, int y, int nodeId) {
		super(nodeId);
		
		this.x = x;
		this.y = y;
	}
	
	public int getX() {
		return x;
	}

	public int getY() {
		return y;
	}


	@Override
	public float getEstimatedCostTo(AStarNode node, AStarNode startNode) {
		AStarNode2D goal = (AStarNode2D)node;
		AStarNode2D start = (AStarNode2D)startNode;
		
		float h = 0;
		
		/*
		 * Manhattan distance heuristics. (no diagonal treatment) 
		 */
		if(heuristic == Heuristic.Manhattan) {
			h = adjacentCost * (Math.abs(x-goal.x) + Math.abs(y-goal.y));
		}
		
		/*
		 * Euclidean distances (move at any angle, again no diagonal treatment).
		 */
		else if(heuristic == Heuristic.Euclidean) {
			h = adjacentCost * (float)Math.sqrt(Math.pow(x-goal.x, 2) + Math.pow(y-goal.y,2));
		}
		
		/*
		 * Diagonal distance heuristic.
		 */
		else if(heuristic == Heuristic.Diagonal || 
				heuristic == Heuristic.DiagonalWithTieBreaking || 
				heuristic == Heuristic.DiagonalWithTieBreakingCrossProduct) {
			float diagonal = Math.min(Math.abs(x-goal.x), Math.abs(y-goal.y));
			float straight = (Math.abs(x-goal.x) + Math.abs(y-goal.y));
			h = (diagonalCost * diagonal) + (adjacentCost * (straight - (2*diagonal)));
			
			
			/*
			 * Normal tie-breaking.
			 */
			if(heuristic == Heuristic.DiagonalWithTieBreaking) {
				h *= (1.0 + tieBreaker);
			}
			
			/*
			 * Add tie-breaking cross-product to the heuristics.
			 * (Produces nicer looking diagonal paths, but weird with obstacles)
			 */
			else if(heuristic == Heuristic.DiagonalWithTieBreakingCrossProduct) {
				float dx1 = x - goal.x;
				float dy1 = y - goal.y;
				float dx2 = start.x - goal.x;
				float dy2 = start.y - goal.y;
				float cross = Math.abs(dx1*dy2 - dx2*dy1);
				h += cross*0.001;
			}
		}

		// Return the heuristic.
		return h;
	}

	@Override
	public float getCost(AStarNode node, Location location) {

		if(heuristic == Heuristic.Manhattan || heuristic == Heuristic.Euclidean) {
			return adjacentCost;
		} else {
			if(location == Location.Adjacent) {
				return adjacentCost;
			} else {
				return diagonalCost;
			}
		}
	}
	

	

}