如何让一只乌龟移动到另一只乌龟的位置?

How to make a turtle move towards another turtle's positions?

我想创建 SpaceInvaders 游戏,但它不会击落敌人,而是朝玩家射击。我使用 .goto() 方法实现它,如下所示:

bullet2.goto(player.xcor(),player.ycor())

但这里的问题是子弹根据玩家的坐标确定了它的目的地,因此卡在了那里。我希望他们继续朝那个方向移动,直到它在敌人可以再次射击后离开屏幕(我没有找到直接的方法来计算 2 个乌龟位置之间的航向)。

我也不知道把 bullet2.goto(player.xcor(),player.ycor()) 命令放在哪里:它应该在 while(True) 的循环中或者在发射子弹的函数中。

我在下面发布我的代码。我的 objective 是这样的:有 2 种不同类型的敌人,一种绕圈移动,而另一种则以正方形移动。第一个敌人在进行 4 次移动后开火,第二个敌人在进行 2 次移动后开火。他们开出的所有东西,子弹都会向玩家移动,除非子弹离开屏幕,否则敌人无法再次开火。

我不是在寻找碰撞。

我知道在使一切都面向对象方面可以改进很多,但现在我专注于游戏的功能。一旦我清除了基本功能,就会这样做。

# python 2.7 and turtle library

import os
import random
import sys
import turtle
turtle.fd(0)
turtle.speed(6)
turtle.bgcolor("black")
turtle.ht()
turtle.setundobuffer(1)
turtle.tracer(1)

class Game():       
    def draw_border(self):
        #Draw border
        self.pen = turtle.Turtle()
        self.pen.speed(0)
        self.pen.color("white")
        self.pen.pensize(3)
        self.pen.penup()
        self.pen.goto(-300, 300)
        self.pen.pendown()
        for side in range(4):
            self.pen.fd(600)
            self.pen.rt(90)
        self.pen.penup()
        self.pen.ht()

game = Game()
game.draw_border()

bulletstate1 = "ready"
bulletstate2 = "ready"

def enemy1_fire():
    #the bullet will travel up from the player's position
    global bulletstate1 # enable modifying global var from inside of function
    if bulletstate1 == "ready":
        bulletstate1 = "fired"
        bullet1.showturtle()
        x = enemy1.xcor() # get the coordinates at the time of firing
        y = enemy1.ycor()
        bullet1.speed = 6
        bullet1.setposition(x,y) # bullet will appear just above the player
        #bullet1.goto(player.xcor(),player.ycor())
        #print(bulletspeed,bullet.xcor(),bullet.ycor(),bulletstate1)

def enemy2_fire():
    #the bullet will travel up from the player's position
    global bulletstate2 # enable modifying global var from inside of function
    if bulletstate2 == "ready":
        bulletstate2 = "fired"
        bullet2.showturtle()
        x = enemy2.xcor()
        y = enemy2.ycor()
        bullet2.speed = 6
        bullet2.setposition(x,y) # bullet will appear just above the player
        #bullet2.goto(player.xcor(),player.ycor())
        #print(bulletspeed,bullet.xcor(),bullet.ycor(),bulletstate2)

class Player(turtle.Turtle):
    def __init__(self, spriteshape, color, startx, starty):
        turtle.Turtle.__init__(self, shape = spriteshape)
        self.speed(3)
        self.penup()
        self.color(color)
        self.fd(0)
        self.goto(startx, starty)
        self.speed = 1
        self.left(90)
        #self.mode("logo")  

    def move(self):
        self.fd(self.speed)
        if (player.xcor()<-280): # boundary checking
            player.setx(-280)
        if (player.xcor()> 280): # boundary checking
            player.setx(280)
        if (player.ycor()<-280): # boundary checking
            player.sety(-280)
        if (player.ycor()> 280): # boundary checking
            player.sety(280)

    def turn_left(self):
        self.move()
        self.lt(30)
        if (player.xcor()<-280): # boundary checking
            player.setx(-280)
        if (player.xcor()> 280): # boundary checking
            player.setx(280)
        if (player.ycor()<-280): # boundary checking
            player.sety(-280)
        if (player.ycor()> 280): # boundary checking
            player.sety(280)

    def turn_right(self):
        self.move()
        self.rt(30)
        if (player.xcor()<-280): # boundary checking
            player.setx(-280)
        if (player.xcor()> 280): # boundary checking
            player.setx(280)
        if (player.ycor()<-280): # boundary checking
            player.sety(-280)
        if (player.ycor()> 280): # boundary checking
            player.sety(280)

    def accelerate(self):
        self.move()
        self.speed = self.speed + 1
        if (player.xcor()<-280): # boundary checking
            player.setx(-280)
        if (player.xcor()> 280): # boundary checking
            player.setx(280)
        if (player.ycor()<-280): # boundary checking
            player.sety(-280)
        if (player.ycor()> 280): # boundary checking
            player.sety(280)

    def brake(self):
        self.speed = self.speed - 1
        if (player.xcor()<-280): # boundary checking
            player.setx(-280)
        if (player.xcor()> 280): # boundary checking
            player.setx(280)
        if (player.ycor()<-280): # boundary checking
            player.sety(-280)
        if (player.ycor()> 280): # boundary checking
            player.sety(280)

class Enemy1(turtle.Turtle):
    def __init__(self, spriteshape, color, startx, starty):
        turtle.Turtle.__init__(self, shape = spriteshape)
        self.speed(3) #animation speed
        self.penup()
        self.color(color)
        self.fd(0)
        self.goto(startx, starty)
        self.speed = 1
        #self.mode("logo")

    shoot = 4 # shoots after 4 interval

    def move(self):
        self.lt(90)
        self.fd(150)
        self.shoot = self.shoot - 1
        if self.shoot==0:
            enemy1_fire() #shoot below, better if can be directed at player
            self.shoot = 4

class Enemy2(turtle.Turtle):
    def __init__(self, spriteshape, color, startx, starty):
        turtle.Turtle.__init__(self, shape = spriteshape)
        self.speed(3)
        self.penup()
        self.color(color)
        self.fd(0)
        self.goto(startx, starty)
        self.speed = 1
        #self.mode("logo")

    shoot = 2 # shoots after 2 interval

    def move(self):
        self.fd(100)
        self.rt(30)
        self.shoot= self.shoot-1
        if self.shoot==0:
            enemy2_fire() #shoot towards player
            self.shoot = 2

enemy1 = Enemy1("circle", "red", 50, -50)
enemy2 = Enemy2("square", "blue", -10, 200)
player = Player("triangle", "white", 0, 0)


#key bindings
turtle.listen()
turtle.onkey(player.turn_left,"Left")
turtle.onkey(player.turn_right,"Right")
turtle.onkey(player.accelerate,"Up")
turtle.onkey(player.brake,"Down")

# create a bullet for the enemy1
bullet1  = turtle.Turtle()
bullet1.color("yellow")
bullet1.shape("triangle")
bullet1.penup()
bullet1.shapesize(0.3,0.3) # length and breadth of bullet
bullet1.hideturtle()
bullet1.speed(3)
bullet1.speed = 2

# create a bullet for the enemy2
bullet2  = turtle.Turtle()
bullet2.color("yellow")
bullet2.shape("square")
bullet2.penup()
bullet2.shapesize(0.4,0.4) # length and breadth of bullet
bullet2.hideturtle()
bullet2.speed(3)
bullet2.speed = 2


while True:
    enemy1.move()
    enemy2.move()

    if bulletstate1=="fired":
        # y = bullet1.ycor()
        # y = y - bullet1.speed
        # bullet1.sety(y)
        bullet1.goto(player.xcor(),player.ycor())

    if bulletstate2=="fired":
        # y = bullet2.ycor()
        # y = y - bullet2.speed
        # bullet2.sety(y)
        bullet2.goto(player.xcor(),player.ycor())

    if (bullet1.ycor()>275 or bullet1.xcor()>275 or bullet1.ycor()<-275 or bullet1.xcor()<-275):
        bullet1.hideturtle()
        # bullet1.sety(enemy1.ycor)
        # bullet1.setx(enemy1.xcor)
        bulletstate1="ready"


    if (bullet2.ycor()>275 or bullet2.xcor()>275 or bullet2.ycor()<-275 or bullet2.xcor()<-275):
        bullet2.hideturtle()
        # bullet2.sety(enemy2.ycor)
        # bullet2.setx(enemy2.xcor)
        bulletstate2="ready"

sys.stdout.close()
delay = raw_input("Press enter to finish. > ")

如果你还有兴趣解决这个问题,你应该解决直角三角形(见图):

        px            
---------|--x--------|
|        |  |        |
|        |  x        |
y--------|-[e]y------y
|        |/ |        |
py-------*py--------py
|       /px |        |
|      / |  |        |
|     /  |  |        |
|    /   |  |        |
|---v----|--x--------|
  y2=-280
  x2=?

[e]为敌人,*为玩家,xy为敌人坐标,pxpy 是玩家的坐标。对于所示的情况,您应该从关系中获得 x2 坐标:
(x-px)/(y-py) = (x-x2)/(y-(-280)) => (x-x2) = (y-(-280))*(x-px)/(y-py) =>
=> x2 = x-(y-(-280))*(x-px)/(y-py),
其中 xypxpyy2 是已知的。

而且你必须考虑玩家和敌人的相对位置,例如:

               px
       ---------|------x----|
       |        |      |    |
       |        |      |    |
       |        |      x    |
       y--------|-- . [e]y--y
       py-------*py----|---py
       |    .   px     |    |
       |  .     |      |    |
y2=?   <. ------|------|----|
x2=-280|        |      |    |
       |--------|------x----|

(x-px)/(y-py) = (x-(-280))/(y-y2) => (y-y2) = (x-(-280))*(y-py)/(x-px) =>
=> y2 = y-(x-(-280))*(y-py)/(x-px),
以及坐标差异的符号。
在您的情况下,这将引导我们使用以下代码(我建议您将其设计为一个单独的函数):

MAX_COOR=330

def bullet_calc(player,x,y):
  diff_x=x-player.xcor()
  diff_y=y-player.ycor()
  if diff_y==0:
    goal_y=y
    if diff_x>0:
      goal_x=-MAX_COOR
    elif diff_x<=0:
      goal_x=MAX_COOR

  elif diff_x==0:
    goal_x=x
    if diff_y>0:
      goal_y=-MAX_COOR
    elif diff_y<=0:
      goal_y=MAX_COOR

  elif diff_x>0 and diff_y>0 and abs(diff_x)<abs(diff_y):  #    |-    - enemy
      goal_x=x-(y-(-MAX_COOR))*diff_x/diff_y               # ---*---  * player
      goal_y=-MAX_COOR                                     #    |

  elif diff_x>0 and diff_y>0 and abs(diff_x)>abs(diff_y):  #    |  _
      goal_x=-MAX_COOR                                     # ---*---
      goal_y=y-(x-(-MAX_COOR))*diff_y/diff_x               #    |

  elif diff_x<0 and diff_y>0 and abs(diff_x)<abs(diff_y):  #   -|    
      goal_x=(y-MAX_COOR)*diff_x/diff_y-x                  # ---*---
      goal_y=-MAX_COOR                                     #    |

  elif diff_x<0 and diff_y>0 and abs(diff_x)>abs(diff_y):  # _  | 
      goal_x=MAX_COOR                                      # ---*---
      goal_y=(x-(-MAX_COOR))*diff_y/diff_x-y               #    |

  elif diff_x>0 and diff_y<0 and abs(diff_x)<abs(diff_y):  #    | 
      goal_x=(y-(-MAX_COOR))*diff_x/diff_y-x               # ---*---
      goal_y=MAX_COOR                                      #    |_

  elif diff_x>0 and diff_y<0 and abs(diff_x)>abs(diff_y):  #    | 
      goal_x=-MAX_COOR                                     # ---*--_
      goal_y=(x-MAX_COOR)*diff_y/diff_x-y                  #    |

  elif diff_x<0 and diff_y<0 and abs(diff_x)<abs(diff_y):  #    | 
      goal_x=x-(y-MAX_COOR)*diff_x/diff_y                  # ---*---
      goal_y=MAX_COOR                                      #   _|

  elif diff_x<0 and diff_y<0 and abs(diff_x)>abs(diff_y):  #    | 
      goal_x=MAX_COOR                                      # _--*---
      goal_y=y-(x-MAX_COOR)*diff_y/diff_x                  #    |

  return (goal_x,goal_y)

而且在发射子弹的函数中调用这段代码似乎更容易:

def enemy1_fire():
    #the bullet will travel up from the player's position
    global bulletstate1 # enable modifying global var from inside of function
    if bulletstate1 == "ready":
        bulletstate1 = "fired"
        x = enemy1.xcor() # get the coordinates at the time of firing
        y = enemy1.ycor()
        bullet1.speed = 6
        bullet1.setposition(x,y) # bullet will appear just above the player
        bullet1.showturtle()     # move <showturtle()> here
        bullet1.goto(bullet_calc(player,x,y))
        #bullet1.goto(player.xcor(), player.ycor())  # your old code

如果球员在场地中央,这一切都会更容易。

而不是做:

if bulletstate1=="fired":
    bullet1.goto(player.xcor(),player.ycor())

你想要的是:

if bulletstate1 == 'fired':
    bullet1.setheading(bullet1.towards(player))
    bullet1.forward(min(10, bullet1.distance(player))

那是在你的运动循环中,在每次迭代中让子弹转向玩家的当前位置并稍微向前移动。如果玩家站着不动,子弹最终会击中他们。如果玩家在移动,子弹会追踪他们。

但是,子弹不太可能"go off the screen"。可能如果前进的步伐非常大:

 bullet1.forward(min(100, bullet1.distance(player))