【Godot4.2】2D导航02 - AstarGrid2D及其使用方法

概述

AstarGrid2D是Godot4.0新增的A*寻路辅助类型。可以看做是Astar2D的加强版。它允许你通过设置其size和cell_size属性来创建一个虚拟的网格。

并使用set_point_solid()这样的方法来在指定位置创建障碍物。

AstarGrid2D的好处是你不再需要手动的添加点以及点与点之间的连接，而是直接用get_point_path()这样的方法来获取最短路径（也就是一个包含了最短路径经过的点的数组）。

通过遍历这个数组，就可以实现路径移动了。

extends Control

var astar_grid = AStarGrid2D.new()

var cell_size = Vector2.ONE * 100

func _ready():
	astar_grid.size = Vector2i.ONE * 32
	astar_grid.cell_size = Vector2i.ONE * 32
	astar_grid.update()
	


func _draw():
	# 绘制网格
	var grid_width = astar_grid.size.x * astar_grid.cell_size.x
	var cell_width = astar_grid.cell_size.x
	var cell_height = astar_grid.cell_size.y
	
	for i in range(astar_grid.size.x):
		draw_line(i * Vector2i(0,cell_height),i * Vector2i(grid_width,cell_height),Color.DARK_OLIVE_GREEN,2)
	for j in range(astar_grid.size.y):
		draw_line(j * Vector2i(cell_height,0),j * Vector2i(cell_height,grid_width),Color.DARK_OLIVE_GREEN,2)
	# 绘制路径和其上的点
	var path  = astar_grid.get_point_path(Vector2i(0,0),Vector2i(10,10))
	for pot in path:
		draw_circle(pot,5,Color.YELLOW)
	draw_polyline(path,Color.YELLOW,2)

extends Control

var astar_grid = AStarGrid2D.new()

var path:PackedVector2Array

var solids = []

func _ready():
	randomize()
	astar_grid.size = Vector2i.ONE * 32
	astar_grid.cell_size = Vector2i.ONE * 32
	astar_grid.offset = astar_grid.cell_size/2
	astar_grid.update()
	
	# 随机生成障碍
	for i in range(50):
		var solid_point = Vector2i(randi_range(0,astar_grid.size.x),randi_range(0,astar_grid.size.y))
		astar_grid.set_point_solid(solid_point,true)
		solids.append(solid_point)
		
	


func _draw():
	var grid_width = astar_grid.size.x * astar_grid.cell_size.x
	var cell_width = astar_grid.cell_size.x
	var cell_height = astar_grid.cell_size.y
	# 绘制网格
	for i in range(astar_grid.size.x):
		draw_line(i * Vector2i(0,cell_height),i * Vector2i(grid_width,cell_height),Color.DARK_OLIVE_GREEN,2)
	for j in range(astar_grid.size.y):
		draw_line(j * Vector2i(cell_height,0),j * Vector2i(cell_height,grid_width),Color.DARK_OLIVE_GREEN,2)
	
	# 绘制路径和其上的点
	if path.size() > 0:
		for pot in path:
			draw_circle(pot,5,Color.YELLOW)
				
		draw_polyline(path,Color.YELLOW,2)
	for p in solids:
		draw_rect(Rect2(p * Vector2i(astar_grid.cell_size),astar_grid.cell_size),Color.GRAY)

func _on_gui_input(event):
	if event is InputEventMouseButton:
		if event.button_index == MOUSE_BUTTON_LEFT:
			if event.is_pressed():
				path = astar_grid.get_point_path(Vector2i(0,0),floor(get_global_mouse_position()/astar_grid.cell_size))
				queue_redraw()

13行：将AstarGrid的offset 设为 astar_grid.cell_size/2,也就实现了整体的坐标偏移。
48行：floor(get_global_mouse_position()/astar_grid.cell_size)获得的就是鼠标点击所在的单元格的坐标。

AstarGrid寻路2.gif
目前为止，AstarGrid显示对角线形式的连接。

如果我们需要设置其只显示横平竖直的连接，则可以设置AstarGrid的diagonal_mode为DIAGONAL_MODE_NEVER。

astar_grid.diagonal_mode = AStarGrid2D.DIAGONAL_MODE_NEVER

AstarGrid寻路3.gif

DiagonalMode	值	说明
DIAGONAL_MODE_ALWAYS	0	该寻路算法将忽略目标单元格周围的实体邻居，并允许沿对角线通过。
DIAGONAL_MODE_NEVER	1	该寻路算法将忽略所有对角线，并且路径始终是正交的。
DIAGONAL_MODE_AT_LEAST_ONE_WALKABLE	2	如果在特定路径段的相邻单元格周围放置了至少两个障碍物，则该寻路算法将避免使用对角线。
DIAGONAL_MODE_ONLY_IF_NO_OBSTACLES	3	如果在特定路径段的相邻单元格周围放置了任意障碍物，则该寻路算法将避免使用对角线。
DIAGONAL_MODE_MAX	4	代表 DiagonalMode 枚举的大小。

实现玩家基于AstarGrid2D的移动

用一个简单Sprite2D作为玩家。将其缩放为原始尺寸128×128的四分之一，也就是32×32。刚好可以填入AstarGrid2D的单元格中。

extends Control

var astar_grid = AStarGrid2D.new()
var path:PackedVector2Array
var solids = [] # 障碍物列表

@onready var icon = $Icon
var speed = 200.0
var can_walk = false
var target_pos:Vector2

func _process(delta):
	if can_walk:
		if path.size()>0:
			target_pos = path[0]
			if icon.position.distance_to(target_pos)>0:
				icon.position = icon.position.move_toward(target_pos,speed * delta)
			else:
				path.remove_at(0)
				queue_redraw()
		else:
			can_walk = false

func _ready():
	randomize()
	astar_grid.size = Vector2i.ONE * 32
	astar_grid.cell_size = Vector2i.ONE * 32
	astar_grid.offset = astar_grid.cell_size/2
	icon.position = astar_grid.cell_size/2
	astar_grid.diagonal_mode = AStarGrid2D.DIAGONAL_MODE_NEVER
	astar_grid.default_compute_heuristic  = AStarGrid2D.HEURISTIC_MANHATTAN

	astar_grid.update()
	
	# 随机生成障碍
	for i in range(150):
		var solid_point = Vector2i(randi_range(0,astar_grid.size.x),randi_range(0,astar_grid.size.y))
		astar_grid.set_point_solid(solid_point,true)
		solids.append(solid_point)
		
	


func _draw():
	var grid_width = astar_grid.size.x * astar_grid.cell_size.x
	var cell_width = astar_grid.cell_size.x
	var cell_height = astar_grid.cell_size.y
	# 绘制网格
	for i in range(astar_grid.size.x):
		draw_line(i * Vector2i(0,cell_height),i * Vector2i(grid_width,cell_height),Color.DARK_OLIVE_GREEN,2)
	for j in range(astar_grid.size.y):
		draw_line(j * Vector2i(cell_height,0),j * Vector2i(cell_height,grid_width),Color.DARK_OLIVE_GREEN,2)
	
	# 绘制路径和其上的点
	if path.size() > 0:
		for pot in path:
			draw_circle(pot,5,Color.YELLOW)
				
		draw_polyline(path,Color.YELLOW,2)
	for p in solids:
		draw_rect(Rect2(p * Vector2i(astar_grid.cell_size),astar_grid.cell_size),Color.GRAY)

func _on_gui_input(event):
	if event is InputEventMouseButton:
		if event.button_index == MOUSE_BUTTON_LEFT:
			if event.is_pressed():
				can_walk = true
				path = astar_grid.get_point_path(floor(icon.position/astar_grid.cell_size),floor(get_global_mouse_position()/astar_grid.cell_size))
				queue_redraw()

每次获取路径的第一个点，利用简单的距离判断和移动，到达后，从路径中删除该点。继续获取路径第一个，如此循环，知道路径中的点删除完毕。

基于AstarGrid2D的简单玩家移动

可行动范围的获取

矩形范围查找法：
先不考虑对角线移动的问题，我们假设玩家可行动点数是4，那么我们只需要遍历一个8×8矩阵的每个点到玩家的是否有可行走的路径，如果有且路径的点数<=4，则标记为可到达的点，否则，标记为不能到达的点。

extends Control

var astar_grid = AStarGrid2D.new()
var path:PackedVector2Array
var solids = [] # 障碍物列表
var max_step:int = 4 # 玩家单次的最大行动点数
var can_walk_rect:Rect2i
var can_walk_points:PackedVector2Array 

@onready var icon = $Icon
var speed = 200.0
var can_walk = false
var target_pos:Vector2

func _process(delta):
	if can_walk:
		if path.size()>0:
			target_pos = path[0]
			if icon.position.distance_to(target_pos)>0:
				icon.position = icon.position.move_toward(target_pos,speed * delta)
			else:
				path.remove_at(0)
				queue_redraw()
		else:
			can_walk = false
			queue_redraw()

func _ready():
	randomize()
	astar_grid.size = Vector2i.ONE * 32
	astar_grid.cell_size = Vector2i.ONE * 32
	astar_grid.offset = astar_grid.cell_size/2
	icon.position = astar_grid.cell_size/2
	astar_grid.diagonal_mode = AStarGrid2D.DIAGONAL_MODE_NEVER

	astar_grid.update()
	
	# 随机生成障碍
	for i in range(150):
		var solid_point = Vector2i(randi_range(0,astar_grid.size.x),randi_range(0,astar_grid.size.y))
		astar_grid.set_point_solid(solid_point,true)
		solids.append(solid_point)

	
	

func _draw():
	var grid_width = astar_grid.size.x * astar_grid.cell_size.x
	var cell_width = astar_grid.cell_size.x
	var cell_height = astar_grid.cell_size.y
	# 绘制网格
	for i in range(astar_grid.size.x):
		draw_line(i * Vector2i(0,cell_height),i * Vector2i(grid_width,cell_height),Color.DARK_OLIVE_GREEN,2)
	for j in range(astar_grid.size.y):
		draw_line(j * Vector2i(cell_height,0),j * Vector2i(cell_height,grid_width),Color.DARK_OLIVE_GREEN,2)
	
	# 绘制路径和其上的点
	if path.size() > 0:
		for pot in path:
			draw_circle(pot,5,Color.YELLOW)
				
		draw_polyline(path,Color.YELLOW,2)
	# 绘制障碍物
	for p in solids:
		draw_rect(Rect2(p * Vector2i(astar_grid.cell_size),astar_grid.cell_size),Color.GRAY)
	# 绘制可行走范围
	# 遍历矩形
	if !can_walk:
		var player_pos = floor(icon.position/astar_grid.cell_size)
		var top_left = clamp(player_pos - Vector2.ONE * max_step,Vector2.ZERO,player_pos)
		var end =  clamp(player_pos + Vector2.ONE * max_step,player_pos,Vector2(astar_grid.size))
		can_walk_rect = Rect2(top_left,end-top_left) # 获取矩形
		for i in range(can_walk_rect.position.x,can_walk_rect.end.x + 1):
			for j in range(can_walk_rect.position.y,can_walk_rect.end.y + 1):
				var v = Vector2(i,j)
				if astar_grid.get_point_path(player_pos,v).size() <= max_step+1:
					if !astar_grid.is_point_solid(v):
						can_walk_points.append(v)
						draw_rect(Rect2(v * astar_grid.cell_size,astar_grid.cell_size),Color.YELLOW_GREEN,false,2)
	
	
	
func _on_gui_input(event):
	if event is InputEventMouseButton:
		if event.button_index == MOUSE_BUTTON_LEFT:
			if event.is_pressed():
				can_walk = true
				var player_pos = floor(icon.position/astar_grid.cell_size)
				var targ_pos = floor(get_global_mouse_position()/astar_grid.cell_size)
				if targ_pos in can_walk_points: # 如果在可行走的范围内
					path = astar_grid.get_point_path(player_pos,targ_pos)
					can_walk_points.clear() # 清空原来的可行走范围
					queue_redraw()