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POWhy does A* not find the optimal path?
 

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  1. POWhy does A* not find the optimal path?
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    <p>I implemented the A*-pathfinding in a simple Winforms application. Where one can also define obstacles on the grid so the agent can navigate around them. </p> <p>The Problem is my agent can't foresee paths. This is why he does not always take the optimal path.</p> <p><a href="http://www.youtube.com/watch?v=em-D-2tvUC4" rel="nofollow">Here you can see my exact problem.</a></p> <p>How can I make the pathfinder anticipate the shorter paths? There is also an issue with dead ends once the agent took the wrong path.</p> <p>This Method gets the adjascent cells and calculates the values:</p> <pre><code>public void addAdjascent(Vector pos) { foreach(Cell cell in allCells) { bool containedInClosedList = closedList.Any(c =&gt; c.id == cell.id); if (!containedInClosedList) { if (cell.positionCR.X == pos.X - 1 &amp;&amp; cell.positionCR.Y == pos.Y) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if(!containedInBlockedList) { cell.H = calcH(goal,cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X + 1 &amp;&amp; cell.positionCR.Y == pos.Y) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X &amp;&amp; cell.positionCR.Y == pos.Y - 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X &amp;&amp; cell.positionCR.Y == pos.Y + 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X - 1 &amp;&amp; cell.positionCR.Y == pos.Y - 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X - 1 &amp;&amp; cell.positionCR.Y == pos.Y + 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X + 1 &amp;&amp; cell.positionCR.Y == pos.Y - 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } if (cell.positionCR.X == pos.X + 1 &amp;&amp; cell.positionCR.Y == pos.Y + 1) { bool containedInBlockedList = blockedList.Any(c =&gt; c.id == cell.id); if (!containedInBlockedList) { cell.H = calcH(goal, cell); cell.G = calcG(start, cell); cell.F = cell.G + cell.H; openList.Add(cell); } } } } } </code></pre> <p>Here is the code for the calculation of G and H values:</p> <pre><code> public int calcG(Vector start,Cell cell) { int distance = closedList.Count; return distance; } public int calcH(Vector goal, Cell cell) { int distance; int distanceX = (goal.X) - cell.positionCR.X; int distanceY = (goal.Y) - cell.positionCR.Y; if (distanceX &lt; 0) { distanceX = distanceX * -1; } if (distanceY &lt; 0) { distanceY = distanceY * -1; } distance = distanceX + distanceY; return distance; } </code></pre> <p>And finally I calculate the next cell I want to step on:</p> <pre><code>public void step() { addAdjascent(stepPos); bool foundDestination = false; int min = 8000; foreach(Cell openCell in openList) { if (openCell.F &lt; min) { min = openCell.F; } } if(openList.Count &gt; 0) { foreach (Cell openCell in openList) { if (openCell.positionCR.X == goal.X &amp;&amp; openCell.positionCR.Y == goal.Y) { closedList.Add(openCell); stepPos = openCell.positionCR; foundDestination = true; } } } if(!foundDestination) { closedList.Add(openList.First(item =&gt; item.F == min)); stepPos = openList.First(item =&gt; item.F == min).positionCR; } openList.Clear(); } </code></pre>
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    1. USRené Wolferink
    1. USチーズパン
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      1. POWhy does A* not find the optimal path?
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      1. VTUpMod
    2. VO
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      1. VTUpMod
    1. COThat belongs to your algorithm problem.
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      1. USKing King
    2. COCan you show us your code?
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      1. USGHC
    3. CO+1 That's utterly cool! Not sure it has anything to do with WinForms though.
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      1. USMathieu Guindon
 

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