这篇文章主要讲解了“C# AStar寻路算法怎么使用”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“C# AStar寻路算法怎么使用”吧！
概述
AStar算法是一种图形搜索算法，常用于寻路。他是以广度优先搜索为基础，集Dijkstra算法和最佳优先(best fit)于一身的一种算法。
示例1:4向
示例2:8向
思路
递归的通过估值函数找到最佳路径，估值函数与距离相关，也有可能与通过代价系数相关（例如平地系数为1，坡地系数为2），有三个参数：
G：起点点到当前点的代价
H: 当前点到终点的代价
F: F = G + H 与最佳路径权重负相关的参数
过程大概：
代码示例
位置定义
public struct Vec2{ public int x; public int y; public Vec2(int x, int y) { this.x = x; this.y = y; } public static Vec2 Zero { get { return new Vec2(0, 0); } } public override bool Equals(object obj) { if (!(obj is Vec2)) return false; var o = (Vec2)obj; return x == o.x && y == o.y; } public override int GetHashCode() { return x.GetHashCode() + y.GetHashCode(); } public static Vec2 operator +(Vec2 a, Vec2 b) { return new Vec2(a.x + b.x, a.y + b.y); } public static Vec2 operator *(Vec2 a, int n) { return new Vec2(a.x * n, a.y * n); } public static Vec2 operator *(int n, Vec2 a) { return new Vec2(a.x * n, a.y * n); } public static bool operator ==(Vec2 a, Vec2 b) { return a.x == b.x && a.y == b.y; } public static bool operator !=(Vec2 a, Vec2 b) { return !(a.x == b.x && a.y == b.y); }}方向定义
public enum EDir{ Up = 0, Down = 1, Left = 2, Right = 3, UpLeft = 4, UpRight = 5, DownLeft = 6, DownRight = 7,}public abstract class CheckDirPol{ abstract public Dictionary<EDir, Vec2> GetDir();}public class CheckDir4Pol : CheckDirPol{ private Dictionary<EDir, Vec2> dirDict = new Dictionary<EDir, Vec2> { {EDir.Up, new Vec2(0, 1) }, {EDir.Down, new Vec2(0, -1) }, {EDir.Left, new Vec2(-1, 0) }, {EDir.Right, new Vec2(1, 0) }, }; override public Dictionary<EDir, Vec2> GetDir() { return dirDict; }}public class CheckDir8Pol : CheckDirPol{ private Dictionary<EDir, Vec2> dirDict = new Dictionary<EDir, Vec2> { {EDir.Up, new Vec2(0, 1) }, {EDir.Down, new Vec2(0, -1) }, {EDir.Left, new Vec2(-1, 0) }, {EDir.Right, new Vec2(1, 0) }, {EDir.UpLeft, new Vec2(-1, 1) }, {EDir.UpRight, new Vec2(1, 1) }, {EDir.DownLeft, new Vec2(-1, -1) }, {EDir.DownRight, new Vec2(1, -1) }, }; override public Dictionary<EDir, Vec2> GetDir() { return dirDict; }}运用策略模式的技巧，以实现4向，8向搜索切换
估值函数
public abstract class EvaPol{abstract public float Calc(Vec2 a, Vec2 b);}public class MANEvaPol : EvaPol{ override public float Calc(Vec2 a, Vec2 b) { return Mathf.Abs(a.x - b.x) + Mathf.Abs(a.y - b.y); }}直接使用曼哈顿距离作为代价
节点定义
public class Node{ public int id; public Vec2 pos; public float g; public float h; public float f; public Vec2 prePos; public bool hasPrePos; public Node(Vec2 pos) { this.pos = pos; } public void SetPrePos(Vec2 pos) { prePos = pos; hasPrePos = true; }}算法上下文定义
Context context;EvaPol disPol;CheckDirPol checkDirPol;public struct Context{ public Vec2 end; public Vec2 start; public Node[,] nodes; public List<Node> open; public List<Node> close; public int[,] map; public List<Vec2> result; public Vec2 size;}寻路算法
初始化
public void Init(Vec2 start, Vec2 end, int[,] map){var x = map.GetLength(0);var y = map.GetLength(1);context = new Context(){start = start,end = end,open = new List<Node>(),close = new List<Node>(),map = map,result = new List<Vec2>(),size = new Vec2(x, y),};context.nodes = new Node[x, y];for (int i = 0; i < x; i++)for (int j = 0; j < x; j++)context.nodes[i, j] = new Node(new Vec2(i, j));disPol = new MANEvaPol();//checkDirPol = new CheckDir4Pol();checkDirPol = new CheckDir8Pol();}获取路径
public List<Vec2> GetResult(){return context.result;}寻路
寻路入口
public void FindPath(){var s = context.start;var sn = context.nodes[s.x, s.y];sn.g = 0;sn.h = disPol.Calc(s, context.end);sn.f = sn.g + sn.h;context.open.Add(sn);FindArrangement(sn);}递归函数
void FindArrangement(Node node){context.close.Add(node);context.open.Remove(node);if (node.pos == context.end){SetResult(node);return;}CheckRound(node);if (context.open.Count == 0)return;Node next = context.open[0];for (int i = 1; i < context.open.Count; i++)if (context.open[i].f < next.f)next = context.open[i];FindArrangement(next);}检查周围节点
void CheckRound(Node node){var dirDict = checkDirPol.GetDir();foreach (var pair in dirDict){var dir = node.pos + pair.Value;if (IsBlock(dir))continue;var dn = context.nodes[dir.x, dir.y];if (context.close.Contains(dn))continue;if (context.open.Contains(dn))TryOverridePath(node, dn);else{dn.g = disPol.Calc(dn.pos, context.start);dn.h = disPol.Calc(dn.pos, context.end);dn.f = dn.g + dn.h;dn.SetPrePos(node.pos);context.open.Add(dn);}}}// 若是从邻节点到该节点路径更优，则替换更新void TryOverridePath(Node a, Node b){var g = a.g + disPol.Calc(a.pos, b.pos);if (g < b.g){b.g = g;b.SetPrePos(a.pos);}}bool IsBlock(Vec2 pos){return !InMap(pos) || context.map[pos.x, pos.y] == 1;}bool InMap(Vec2 pos){var x = pos.x;var y = pos.y;var size = context.size;return x >= 0 && x < size.x && y >= 0 && y < size.y;}生成路径
void SetResult(Node node){Queue<Node> q = new Queue<Node>();while(node.hasPrePos){q.Enqueue(node);node = context.nodes[node.prePos.x, node.prePos.y];}while(q.Count > 0){context.result.Add(q.Dequeue().pos);}}完整代码
using System.Collections;using System.Collections.Generic;using UnityEngine;public struct Vec2{ public int x; public int y; public Vec2(int x, int y) { this.x = x; this.y = y; } public static Vec2 Zero { get { return new Vec2(0, 0); } } public override bool Equals(object obj) { if (!(obj is Vec2)) return false; var o = (Vec2)obj; return x == o.x && y == o.y; } public override int GetHashCode() { return x.GetHashCode() + y.GetHashCode(); } public static Vec2 operator +(Vec2 a, Vec2 b) { return new Vec2(a.x + b.x, a.y + b.y); } public static Vec2 operator *(Vec2 a, int n) { return new Vec2(a.x * n, a.y * n); } public static Vec2 operator *(int n, Vec2 a) { return new Vec2(a.x * n, a.y * n); } public static bool operator ==(Vec2 a, Vec2 b) { return a.x == b.x && a.y == b.y; } public static bool operator !=(Vec2 a, Vec2 b) { return !(a.x == b.x && a.y == b.y); }}public enum EDir{ Up = 0, Down = 1, Left = 2, Right = 3, UpLeft = 4, UpRight = 5, DownLeft = 6, DownRight = 7,}public class AstarFindPath{ public class Node { public int id; public Vec2 pos; public float g; public float h; public float f; public Vec2 prePos; public bool hasPrePos; public Node(Vec2 pos) { this.pos = pos; } public void SetPrePos(Vec2 pos) { prePos = pos; hasPrePos = true; } } public abstract class EvaPol { abstract public float Calc(Vec2 a, Vec2 b); } public class MANEvaPol : EvaPol { override public float Calc(Vec2 a, Vec2 b) { return Mathf.Abs(a.x - b.x) + Mathf.Abs(a.y - b.y); } } public abstract class CheckDirPol { abstract public Dictionary<EDir, Vec2> GetDir(); } public class CheckDir4Pol : CheckDirPol { private Dictionary<EDir, Vec2> dirDict = new Dictionary<EDir, Vec2> { {EDir.Up, new Vec2(0, 1) }, {EDir.Down, new Vec2(0, -1) }, {EDir.Left, new Vec2(-1, 0) }, {EDir.Right, new Vec2(1, 0) }, }; override public Dictionary<EDir, Vec2> GetDir() { return dirDict; } } public class CheckDir8Pol : CheckDirPol { private Dictionary<EDir, Vec2> dirDict = new Dictionary<EDir, Vec2> { {EDir.Up, new Vec2(0, 1) }, {EDir.Down, new Vec2(0, -1) }, {EDir.Left, new Vec2(-1, 0) }, {EDir.Right, new Vec2(1, 0) }, {EDir.UpLeft, new Vec2(-1, 1) }, {EDir.UpRight, new Vec2(1, 1) }, {EDir.DownLeft, new Vec2(-1, -1) }, {EDir.DownRight, new Vec2(1, -1) }, }; override public Dictionary<EDir, Vec2> GetDir() { return dirDict; } } public struct Context { public Vec2 end; public Vec2 start; public Node[,] nodes; public List<Node> open; public List<Node> close; public int[,] map; public List<Vec2> result; public Vec2 size; } Context context; EvaPol disPol; CheckDirPol checkDirPol; public void Init(Vec2 start, Vec2 end, int[,] map) { var x = map.GetLength(0); var y = map.GetLength(1); context = new Context() { start = start, end = end, open = new List<Node>(), close = new List<Node>(), map = map, result = new List<Vec2>(), size = new Vec2(x, y), }; context.nodes = new Node[x, y]; for (int i = 0; i < x; i++) for (int j = 0; j < x; j++) context.nodes[i, j] = new Node(new Vec2(i, j)); disPol = new MANEvaPol(); //checkDirPol = new CheckDir4Pol(); checkDirPol = new CheckDir8Pol(); } public void FindPath() { var s = context.start; var sn = context.nodes[s.x, s.y]; sn.g = 0; sn.h = disPol.Calc(s, context.end); sn.f = sn.g + sn.h; context.open.Add(sn); FindArrangement(sn); } public List<Vec2> GetResult() { return context.result; } void FindArrangement(Node node) { context.close.Add(node); context.open.Remove(node); if (node.pos == context.end) { SetResult(node); return; } CheckRound(node); if (context.open.Count == 0) return; Node next = context.open[0]; for (int i = 1; i < context.open.Count; i++) if (context.open[i].f < next.f) next = context.open[i]; FindArrangement(next); } void SetResult(Node node) { Queue<Node> q = new Queue<Node>(); while(node.hasPrePos) { q.Enqueue(node); node = context.nodes[node.prePos.x, node.prePos.y]; } while(q.Count > 0) { context.result.Add(q.Dequeue().pos); } } void CheckRound(Node node) { var dirDict = checkDirPol.GetDir(); foreach (var pair in dirDict) { var dir = node.pos + pair.Value; if (IsBlock(dir)) continue; var dn = context.nodes[dir.x, dir.y]; if (context.close.Contains(dn)) continue; if (context.open.Contains(dn)) TryOverridePath(node, dn); else { dn.g = disPol.Calc(dn.pos, context.start); dn.h = disPol.Calc(dn.pos, context.end); dn.f = dn.g + dn.h; dn.SetPrePos(node.pos); context.open.Add(dn); } } } void TryOverridePath(Node a, Node b) { var g = a.g + disPol.Calc(a.pos, b.pos); if (g < b.g) { b.g = g; b.SetPrePos(a.pos); } } bool IsBlock(Vec2 pos) { return !InMap(pos) || context.map[pos.x, pos.y] == 1; } bool InMap(Vec2 pos) { var x = pos.x; var y = pos.y; var size = context.size; return x >= 0 && x < size.x && y >= 0 && y < size.y; }}感谢各位的阅读，以上就是“C# AStar寻路算法怎么使用”的内容了，经过本文的学习后，相信大家对C# AStar寻路算法怎么使用这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是编程网，小编将为大家推送更多相关知识点的文章，欢迎关注！
