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Modified the AStar path algorithm to use the geometric distance to the

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goal as its distance estimate and to assign a higher cost to diagonal
traversal than to orthogonal traversal.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@961 542714f4-19e9-0310-aa3c-eee0fc999fb1
This commit is contained in:
Michael Bayne
2002-02-07 19:57:24 +00:00
parent 6c35ab42ec
commit 39db06672b
1 changed files with 25 additions and 22 deletions
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src/java/com/threerings/miso/client/util/AStarPathUtil.java
+25 -22
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@@ -1,5 +1,5 @@
//
// $Id: AStarPathUtil.java,v 1.10 2001/11/29 23:35:59 mdb Exp $
// $Id: AStarPathUtil.java,v 1.11 2002/02/07 19:57:24 mdb Exp $
package com.threerings.miso.scene.util;
@@ -75,14 +75,14 @@ public class AStarPathUtil
// are impassable.
// consider each successor of the node
considerStep(info, n, n.x - 1, n.y - 1);
considerStep(info, n, n.x, n.y - 1);
considerStep(info, n, n.x + 1, n.y - 1);
considerStep(info, n, n.x - 1, n.y);
considerStep(info, n, n.x + 1, n.y);
considerStep(info, n, n.x - 1, n.y + 1);
considerStep(info, n, n.x, n.y + 1);
considerStep(info, n, n.x + 1, n.y + 1);
considerStep(info, n, n.x - 1, n.y - 1, 14);
considerStep(info, n, n.x, n.y - 1, 10);
considerStep(info, n, n.x + 1, n.y - 1, 14);
considerStep(info, n, n.x - 1, n.y, 10);
considerStep(info, n, n.x + 1, n.y, 10);
considerStep(info, n, n.x - 1, n.y + 1, 14);
considerStep(info, n, n.x, n.y + 1, 10);
considerStep(info, n, n.x + 1, n.y + 1, 14);
// push the node on the closed list
info.closed.add(n);
@@ -102,16 +102,15 @@ public class AStarPathUtil
* @param y the y-coordinate for the destination step.
*/
protected static void considerStep (
AStarInfo info, AStarNode n, int x, int y)
AStarInfo info, AStarNode n, int x, int y, int cost)
{
// skip node if it's outside the map bounds or otherwise impassable
if (!isStepValid(info, n.x, n.y, x, y)) {
return;
}
// calculate the new cost for this node. the cost to go
// node-to-node is always 1 for now.
int newg = n.g + 1;
// calculate the new cost for this node
int newg = n.g + cost;
// retrieve the node corresponding to this location
AStarNode np = getNode(info, x, y);
@@ -238,12 +237,16 @@ public class AStarPathUtil
}
/**
* Return a heuristic estimate of the cost to get from
* <code>(ax, ay)</code> to <code>(bx, by)</code>.
* Return a heuristic estimate of the cost to get from <code>(ax,
* ay)</code> to <code>(bx, by)</code>.
*/
protected static int getDistanceEstimate (int ax, int ay, int bx, int by)
{
return Math.max(Math.abs(bx - ax), Math.abs(by - ay));
// we're doing all of our cost calculations based on geometric
// distance times ten
int xsq = 10 * (bx - ax); xsq = xsq * xsq;
int ysq = 10 * (by - ay); ysq = ysq * ysq;
return (int)Math.sqrt(xsq + ysq);
}
}
@@ -330,12 +333,12 @@ class AStarNode implements Comparable
{
int bf = ((AStarNode)o).f;
// since the set contract is fulfilled using the equality
// results returned here, and we'd like to allow multiple
// nodes with equivalent scores in our set, we explicitly
// define object equivalence as the result of object.equals(),
// else we use the unique node id since it will return a
// consistent ordering for the objects.
// since the set contract is fulfilled using the equality results
// returned here, and we'd like to allow multiple nodes with
// equivalent scores in our set, we explicitly define object
// equivalence as the result of object.equals(), else we use the
// unique node id since it will return a consistent ordering for
// the objects.
if (f == bf) {
return (this == o) ? 0 : (id - ((AStarNode)o).id);
}