Pygame: Making a sprite move along a predetermined path at a constant speed

问题

I'm working on a tower defense game in Pygame in which the enemies advance towards the base along a path that I have set for them; if you've played flash games like VR Defender Y3K and Canyon Defense my idea is the exact same concept. However, I am having trouble getting the sprites to move along a path that involves changes in direction such as the path turning left or right.

So my question is what is an easy way to get a sprite to move along a predetermined path with changes in direction at a constant speed?

Edit: Here's the code I have so far.

#Project 2 v1.00
import pygame, sys, time
from math import *
from pygame.locals import *

WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
BLUE = (0, 255, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)

surface = pygame.display.set_mode((500,500),0, 30)

class PlaceHolder:
    def __init__(self, win, left, top, width, height, color):
        self.win = win
        self.rect = pygame.Rect(left, top, width, height)
        self.color = color

    def move(self,x,y,duration):
        #self.rect = self.rect.move(self.velocity[0],self.velocity[1])
        xpointlist = [60, 60]
        ypointlist = [236, 136]
        self.rect.left += x
        self.rect.top += y
        self.duration = duration
        counter = 0
        rate = 10
        for counter in range(len(xpointlist)-1):
            dx = x - xpointlist[counter]
            dy = y - ypointlist[counter]
            distance = sqrt(dx*dx + dy*dy)
            return distance
        duration = distance/rate

    def draw(self):
        pygame.draw.ellipse(surface, self.color, self.rect, 0)

class projectWin:
    def __init__(self, width, height, caption):
        self.caption = caption
        pygame.display.set_caption(self.caption)
        self.width = width
        self.height = height
        self.placeHolders = []
        self.placeHolders.append(PlaceHolder(surface, 1, 236, 10, 10, GREEN))
        #placeHolder1 = PlaceHolder(surface, 10, 236, 10, 10, GREEN)

    def grid(self):
        for i in range(24, 499, 25): #draw the vertical lines
            pygame.draw.line(surface, WHITE, (i, 0), (i, 499), 1)
        for j in range(24, 499, 25): #draw the horizontal lines
        pygame.draw.line(surface, WHITE, (0, j), (499, j), 1)

    def path(self):
        #the two lines are separated for ease of change
        #line 1
        pygame.draw.line(surface, GREEN, (0, 224), (49, 224), 2)
        pygame.draw.line(surface, GREEN, (49, 224), (49, 149), 2)
        pygame.draw.line(surface, GREEN, (49, 149), (349, 149), 2)
        pygame.draw.line(surface, GREEN, (349, 149), (349, 274), 2)
        pygame.draw.line(surface, GREEN, (349, 274), (99, 274), 2)
        pygame.draw.line(surface, GREEN, (99, 274), (99, 349), 2)
        pygame.draw.line(surface, GREEN, (99, 349), (374, 349), 2)
        pygame.draw.line(surface, GREEN, (374, 349), (374, 224), 2)
        pygame.draw.line(surface, GREEN, (374, 224), (499, 224), 2)

        #line 2
        pygame.draw.line(surface, GREEN, (0, 249), (74, 249), 2)
        pygame.draw.line(surface, GREEN, (74, 249), (74, 174), 2)
        pygame.draw.line(surface, GREEN, (74, 174), (324, 174), 2)
        pygame.draw.line(surface, GREEN, (324, 174), (324, 249), 2)
        pygame.draw.line(surface, GREEN, (324, 249), (75, 249), 2)
        pygame.draw.line(surface, GREEN, (74, 249), (74, 374), 2)
        pygame.draw.line(surface, GREEN, (74, 374), (399, 374), 2)
        pygame.draw.line(surface, GREEN, (399, 374), (399, 249), 2)
        pygame.draw.line(surface, GREEN, (399, 249), (499, 249), 2)

    def base(self): #what the player has to protect
        base = pygame.Rect(474, 187, 99, 99)
        pygame.draw.ellipse(surface, BLUE, base, 0)

pygame.init()

win = projectWin(500, 500, 'Project 2 v1.00')
Quit = False
while not Quit:
    surface.fill(BLACK)
    #draw the grid, path, and base on the screen
    win.grid()
    win.path()
    win.base()
    for i in win.placeHolders: #draw and move the placeholder enemy assets
        i.move(59, 0, duration)
        i.move(0, -100, duration)
        i.draw()
    pygame.display.update()
    time.sleep(0.02)
    for event in pygame.event.get():
        if event.type == QUIT:
            Quit = True

pygame.quit() #always exit cleanly
sys.exit()

回答1:

I can better my answer if you supply some code, but I can give you some insight:

In a game like you are trying to make, you can make the following:

xdirection = 1
ydirection = 1

you can multiply the directions by the amount they should be going in the direction to control a sprite. The faster you want them to go, the larger the direction number should be. You can use positive and negative to control which way they will be going.

Again, this response was completely speculative because you have displayed no code. Please let me know if this was not helpful and I will try and change my response accordingly.

来源：https://stackoverflow.com/questions/20025367/pygame-making-a-sprite-move-along-a-predetermined-path-at-a-constant-speed

标签

python

pygame