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Pathfinder: Only consider useful neighbors

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Depending on the direction we came from, many neighbors are completely
useless. This is the first step to implementing the ideas in 'Jump Point
Search'

V2: Added comment describing what the array is for.
This commit is contained in:
Chris Forbes
2014-11-22 17:06:55 +13:00
parent c470945db7
commit f4e5c63408
1 changed files with 28 additions and 2 deletions
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30
OpenRA.Mods.RA/Move/PathSearch.cs
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@@ -138,6 +138,32 @@ namespace OpenRA.Mods.RA.Move
return this; return this;
} }
// Sets of neighbors for each incoming direction. These exclude the neighbors which are guaranteed
// to be reached more cheaply by a path through our parent cell which does not include the current cell.
// For horizontal/vertical directions, the set is the three cells 'ahead'. For diagonal directions, the set
// is the three cells ahead, plus the two cells to the side, which we cannot exclude without knowing if
// the cell directly between them and our parent is passable.
static CVec[][] DirectedNeighbors = {
new CVec[] { new CVec(-1, -1), new CVec(0, -1), new CVec(1, -1), new CVec(-1, 0), new CVec(-1, 1) },
new CVec[] { new CVec(-1, -1), new CVec(0, -1), new CVec(1, -1) },
new CVec[] { new CVec(-1, -1), new CVec(0, -1), new CVec(1, -1), new CVec(1, 0), new CVec(1, 1) },
new CVec[] { new CVec(-1, -1), new CVec(-1, 0), new CVec(-1, 1) },
CVec.directions,
new CVec[] { new CVec(1, -1), new CVec(1, 0), new CVec(1, 1) },
new CVec[] { new CVec(-1, -1), new CVec(-1, 0), new CVec(-1, 1), new CVec(0, 1), new CVec(1, 1) },
new CVec[] { new CVec(-1, 1), new CVec(0, 1), new CVec(1, 1) },
new CVec[] { new CVec(1, -1), new CVec(1, 0), new CVec(-1, 1), new CVec(0, 1), new CVec(1, 1) },
};
static CVec[] GetNeighbors(CPos p, CPos prev)
{
var dx = p.X - prev.X;
var dy = p.Y - prev.Y;
var index = dy * 3 + dx + 4;
return DirectedNeighbors[index];
}
public CPos Expand(World world) public CPos Expand(World world)
{ {
var p = Queue.Pop(); var p = Queue.Pop();
@@ -165,10 +191,10 @@ namespace OpenRA.Mods.RA.Move
return p.Location; return p.Location;
} }
// This current cell is ok; check all immediate directions: // This current cell is ok; check useful immediate directions:
Considered.Add(p.Location); Considered.Add(p.Location);
var directions = CVec.directions; var directions = GetNeighbors(p.Location, pCell.Path);
for (var i = 0; i < directions.Length; ++i) for (var i = 0; i < directions.Length; ++i)
{ {