如何让一只乌龟向另一只乌龟的位置移动？

Question

我想创建太空入侵者的游戏，但不是敌人射击下来，它会朝玩家射击。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来确定它的目的地，因此被卡在那里。我想让他们继续朝那个方向移动，直到它离开屏幕，这时敌人可以再次射击（我没有找到一个直接的方法来计算两个海龟位置之间的航向）。你知道吗

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，或者在触发项目符号的函数中。你知道吗

我把我的代码贴在下面。我的目标是：有两种不同类型的敌人，一个在圆圈里移动，另一个在正方形里移动。第一个敌人4步后开火，第二个敌人2步后开火。所有他们发射的东西，子弹都会向玩家移动，除非子弹离开屏幕，否则敌人不能再开火。你知道吗

我不是在找碰撞。你知道吗

我知道在使一切都面向对象方面有很多可以改进的地方，但是现在我把重点放在游戏的功能上。一旦我清除了基本功能，我就会这么做。你知道吗

# 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. > ")

Answer 1

如果你还想解决这个问题，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=?

设[e]为敌，*为玩家，x和y为敌坐标，px和py为玩家坐标。对于所示的情况，应该从关系中获取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)，
其中已知x、y、px、py和y2。你知道吗

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，这将引导我们找到以下代码（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)

在触发项目符号的函数中调用此代码似乎更容易：

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，这一切就容易多了。你知道吗