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diff --git a/manuals/chickadee/Path-Finding.html b/manuals/chickadee/Path-Finding.html deleted file mode 100644 index 150ef88..0000000 --- a/manuals/chickadee/Path-Finding.html +++ /dev/null @@ -1,171 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> -<html> -<!-- Copyright (C) 2017-2023 David Thompson dthompson2@worcester.edu - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 -or any later version published by the Free Software Foundation; -with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. -A copy of the license is included in the section entitled "GNU -Free Documentation License". - -A copy of the license is also available from the Free Software -Foundation Web site at http://www.gnu.org/licenses/fdl.html. - - -* Chickadee: (chickadee). Game programming toolkit for Guile. - -The document was typeset with -http://www.texinfo.org/ (GNU Texinfo). - --> -<!-- Created by GNU Texinfo 6.7, http://www.gnu.org/software/texinfo/ --> -<head> -<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> -<title>Path Finding (The Chickadee Game Toolkit)</title> - -<meta name="description" content="Path Finding (The Chickadee Game Toolkit)" /> -<meta name="keywords" content="Path Finding (The Chickadee Game Toolkit)" /> -<meta name="resource-type" content="document" /> -<meta name="distribution" content="global" /> -<meta name="Generator" content="makeinfo" /> -<link href="index.html" rel="start" title="Top" /> -<link href="Index.html" rel="index" title="Index" /> -<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents" /> -<link href="Data-Structures.html" rel="up" title="Data Structures" /> -<link href="Copying-This-Manual.html" rel="next" title="Copying This Manual" /> -<link href="Grids.html" rel="prev" title="Grids" /> -<style type="text/css"> -<!-- -a.summary-letter {text-decoration: none} -blockquote.indentedblock {margin-right: 0em} -div.display {margin-left: 3.2em} -div.example {margin-left: 3.2em} -div.lisp {margin-left: 3.2em} -kbd {font-style: oblique} -pre.display {font-family: inherit} -pre.format {font-family: inherit} -pre.menu-comment {font-family: serif} -pre.menu-preformatted {font-family: serif} -span.nolinebreak {white-space: nowrap} -span.roman {font-family: initial; font-weight: normal} -span.sansserif {font-family: sans-serif; font-weight: normal} -ul.no-bullet {list-style: none} -@media (min-width: 1140px) { - body { - margin-left: 14rem; - margin-right: 4rem; - max-width: 52rem; - } -} - -@media (min-width: 800px) and (max-width: 1140px) { - body { - margin-left: 6rem; - margin-right: 4rem; - max-width: 52rem; - } -} - -@media (max-width: 800px) { - body { - margin: 1rem; - } -} - ---> -</style> -<link rel="stylesheet" type="text/css" href="https://dthompson.us/css/dthompson.css" /> - - -</head> - -<body lang="en"> -<span id="Path-Finding"></span><div class="header"> -<p> -Previous: <a href="Grids.html" accesskey="p" rel="prev">Grids</a>, Up: <a href="Data-Structures.html" accesskey="u" rel="up">Data Structures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p> -</div> -<hr /> -<span id="Path-Finding-1"></span><h4 class="subsection">5.6.6 Path Finding</h4> - -<p>Most game worlds have maps. Often, these games have a need to move -non-player characters around in an unscripted fashion. For example, -in a real-time strategy game, the player may command one of their -units to attack something in the enemy base. To do so, the unit must -calculate the shortest route to get there. It wouldn’t be a very fun -game if units didn’t know how to transport themselves efficiently. -This is where path finding algorithms come in handy. The -<code>(chickadee data path-finding)</code> module provides a generic -implementation of the popular A* path finding algorithm. Just add a -map implementation! -</p> -<p>The example below defines a very simple town map and finds the -quickest way to get from the town common to the school. -</p> -<div class="lisp"> -<pre class="lisp"><span class="syntax-open">(</span><span class="syntax-special">define</span> <span class="syntax-symbol">world-map</span> - <span class="syntax-symbol">'</span><span class="syntax-open">(</span><span class="syntax-open">(</span><span class="syntax-symbol">town-common</span> <span class="syntax-symbol">.</span> <span class="syntax-open">(</span><span class="syntax-symbol">town-hall</span> <span class="syntax-special">library</span><span class="syntax-close">)</span><span class="syntax-close">)</span> - <span class="syntax-open">(</span><span class="syntax-symbol">town-hall</span> <span class="syntax-symbol">.</span> <span class="syntax-open">(</span><span class="syntax-symbol">town-common</span> <span class="syntax-symbol">school</span><span class="syntax-close">)</span><span class="syntax-close">)</span> - <span class="syntax-open">(</span><span class="syntax-special">library</span> <span class="syntax-symbol">.</span> <span class="syntax-open">(</span><span class="syntax-symbol">town-common</span> <span class="syntax-symbol">cafe</span><span class="syntax-close">)</span><span class="syntax-close">)</span> - <span class="syntax-open">(</span><span class="syntax-symbol">school</span> <span class="syntax-symbol">.</span> <span class="syntax-open">(</span><span class="syntax-symbol">town-hall</span> <span class="syntax-symbol">cafe</span><span class="syntax-close">)</span><span class="syntax-close">)</span> - <span class="syntax-open">(</span><span class="syntax-symbol">cafe</span> <span class="syntax-symbol">.</span> <span class="syntax-open">(</span><span class="syntax-special">library</span> <span class="syntax-symbol">school</span><span class="syntax-close">)</span><span class="syntax-close">)</span><span class="syntax-close">)</span><span class="syntax-close">)</span> -<span class="syntax-open">(</span><span class="syntax-special">define</span> <span class="syntax-open">(</span><span class="syntax-symbol">neighbors</span> <span class="syntax-symbol">building</span><span class="syntax-close">)</span> - <span class="syntax-open">(</span><span class="syntax-symbol">assq-ref</span> <span class="syntax-symbol">town-map</span> <span class="syntax-symbol">building</span><span class="syntax-close">)</span><span class="syntax-close">)</span> -<span class="syntax-open">(</span><span class="syntax-special">define</span> <span class="syntax-open">(</span><span class="syntax-symbol">cost</span> <span class="syntax-symbol">a</span> <span class="syntax-symbol">b</span><span class="syntax-close">)</span> <span class="syntax-symbol">1</span><span class="syntax-close">)</span> -<span class="syntax-open">(</span><span class="syntax-special">define</span> <span class="syntax-open">(</span><span class="syntax-symbol">distance</span> <span class="syntax-symbol">a</span> <span class="syntax-symbol">b</span><span class="syntax-close">)</span> <span class="syntax-symbol">1</span><span class="syntax-close">)</span> -<span class="syntax-open">(</span><span class="syntax-special">define</span> <span class="syntax-symbol">pf</span> <span class="syntax-open">(</span><span class="syntax-symbol">make-path-finder</span><span class="syntax-close">)</span><span class="syntax-close">)</span> -<span class="syntax-open">(</span><span class="syntax-symbol">a*</span> <span class="syntax-symbol">pf</span> <span class="syntax-symbol">'town-common</span> <span class="syntax-symbol">'school</span> <span class="syntax-symbol">neighbors</span> <span class="syntax-symbol">cost</span> <span class="syntax-symbol">distance</span><span class="syntax-close">)</span> -</pre></div> - -<p>In this case, the <code>a*</code> procedure will return the list -<code>(town-common town-hall school)</code>, which is indeed the shortest -route. (The other possible route is <code>(town-common library cafe -school)</code>.) -</p> -<p>The <code>a*</code> procedure does not know anything about about any kind of -map and therefore must be told how to look up neighboring nodes, which -is what the <code>neighbors</code> procedure in the example does. To -simulate different types of terrain, a cost procedure is used. In -this example, it is just as easy to move between any two nodes because -<code>cost</code> always returns 1. In a real game, perhaps moving from -from a field to a rocky hill would cost a lot more than moving from -one field to another. Finally, a heuristic is used to calculate an -approximate distance between two nodes on the map. In this simple -association list based graph it is tough to calculate a distance -between nodes, so the <code>distance</code> procedure isn’t helpful and -always returns 1. In a real game with a tile-based map, for example, -the heuristic could be a quick Manhattan distance calculation based on -the coordinates of the two map tiles. Choose an appropriate heuristic -for optimal path finding! -</p> -<dl> -<dt id="index-make_002dpath_002dfinder">Procedure: <strong>make-path-finder</strong></dt> -<dd><p>Return a new path finder object. -</p></dd></dl> - -<dl> -<dt id="index-path_002dfinder_003f">Procedure: <strong>path-finder?</strong> <em>obj</em></dt> -<dd><p>Return <code>#t</code> if <var>obj</var> is a path finder. -</p></dd></dl> - -<dl> -<dt id="index-a_002a">Procedure: <strong>a*</strong> <em>path-finder start goal neighbors cost distance</em></dt> -<dd> -<p>Return a list of nodes forming a path from <var>start</var> to <var>goal</var> -using <var>path-finder</var> to hold state. <var>neighbors</var> is a procedure -that accepts a node and returns a list of nodes that neighbor it. -<var>cost</var> is a procedure that accepts two neighboring nodes and -returns the cost of moving from the first to the second as a real -number. <var>distance</var> is a procedure that accepts two nodes and -returns an approximate distance between them. -</p></dd></dl> - -<hr /> -<div class="header"> -<p> -Previous: <a href="Grids.html" accesskey="p" rel="prev">Grids</a>, Up: <a href="Data-Structures.html" accesskey="u" rel="up">Data Structures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html" title="Index" rel="index">Index</a>]</p> -</div> - - - -</body> -</html> |