在python pygame中使用cos()和sin()以恒定的速度从玩家发射粒子 [英] Firing particles from a player at a constant speed with cos() and sin() in python pygame

问题描述

在python pygame中，我试图使我的玩家从玩家中心开始朝着鼠标的方向射击粒子

  class粒子:def __init __(self，...，dx，dy，x，y):self.dx = dxself.dy = dyself.x = xself.y = yself.Rect = self.img.get_rect()def draw():self.x + = self.dxself.y + = self.dyself.Rect.centerx = self.xself.Rect.centery = self.yscreen.blit(self.img，(self.Rect.x，self.Rect.y)) 

theta是播放器中心与鼠标之间的夹角，以度为单位，范围为0到360，0为正x方向

  dx = math.cos(theta)dy = math.sin(theta)粒子(...，dx，dy，starting_x，starting_y) 

但是粒子似乎在随机方向上发射?

完整代码:

  import pygame导入数学FPS = 60白=(255，255，255)红色=(255，0，0)蓝色=(0，0，255)pygame.init()屏幕= pygame.display.set_mode([300，300])时钟= pygame.time.Clock()类粒子:def __init __(self，dx，dy，x，y):self.dx = dxself.dy = dyself.x = xself.y = yself.Rect = pygame.Rect(100，150，5，5)def画图(自己，屏幕):self.x + = self.dxself.y + = self.dyself.Rect.centerx = self.xself.Rect.centery = self.ypygame.draw.rect(screen，BLUE，self.Rect)粒子= []完成=错误未完成时:screen.fill(白色)对于pygame.event.get()中的事件:如果event.type == pygame.QUIT:完成=正确如果pygame.mouse.get_pressed()[0]:mousex = pygame.mouse.get_pos()[0]mousey = pygame.mouse.get_pos()[1]theta =数学度(math.atan(player_rect.x-mousey/player_rect.y-mousex))dx = math.cos(theta)dy = math.sin(theta)particle.append(Particle(dx，dy，player_rect.x，player_rect.y))对于粒子中的粒子:粒子绘制(屏幕)player_rect = pygame.Rect(100，150，10，10)pygame.draw.rect(screen，RED，player_rect)clock.tick(FPS)pygame.display.update()pygame.quit() 

解决方案

无需计算角度.只需计算归一化方向(

  import pygame导入数学FPS = 60白=(255，255，255)红色=(255，0，0)蓝色=(0，0，255)pygame.init()屏幕= pygame.display.set_mode([300，300])时钟= pygame.time.Clock()类粒子:def __init __(self，dx，dy，x，y):self.dx = dxself.dy = dyself.x = xself.y = yself.Rect = pygame.Rect(100，150，5，5)def画图(自己，屏幕):self.x + = self.dxself.y + = self.dyself.Rect.centerx = self.xself.Rect.centery = self.ypygame.draw.rect(screen，BLUE，self.Rect)粒子= []完成=错误未完成时:screen.fill(白色)对于pygame.event.get()中的事件:如果event.type == pygame.QUIT:完成=正确如果pygame.mouse.get_pressed()[0]:mousex = pygame.mouse.get_pos()[0]mousey = pygame.mouse.get_pos()[1]dx，dy = mousex-player_rect.centerx，mousey-player_rect.centerylen = math.hypot(dx，dy)如果len>0:particle.append(Particle(dx/len，dy/len，* player_rect.center))对于粒子中的粒子:粒子绘制(屏幕)player_rect = pygame.Rect(100，150，10，10)pygame.draw.rect(screen，RED，player_rect)pygame.display.flip()clock.tick(FPS)pygame.quit() 

In python pygame I'm trying to make my player shoot a particle in the direction of the mouse, starting at the players centre

class Particle:
    def __init__(self, ..., dx, dy, x, y):
        self.dx = dx
        self.dy = dy
        self.x = x
        self.y = y
        self.Rect = self.img.get_rect()

    def draw(self):
        self.x += self.dx
        self.y += self.dy
        self.Rect.centerx = self.x
        self.Rect.centery = self.y
        screen.blit(self.img, (self.Rect.x, self.Rect.y))

theta is the angle between the centre of the player and the mouse in degrees, ranging from 0 to 360, 0 being the positive x direction

dx = math.cos(theta) 
dy = math.sin(theta)
Particle(..., dx, dy, starting_x, starting_y)

However the particles seem to fire in random directions?

Full code:

import pygame
import math

FPS = 60
WHITE = (255, 255, 255)
RED = (255, 0, 0)
BLUE = (0, 0, 255)

pygame.init()

screen = pygame.display.set_mode([300, 300])

clock = pygame.time.Clock()

class Particle:
    def __init__(self, dx, dy, x, y):
        self.dx = dx
        self.dy = dy
        self.x = x
        self.y = y
        self.Rect = pygame.Rect(100, 150, 5, 5)


    def draw(self, screen):
        self.x += self.dx
        self.y += self.dy
        self.Rect.centerx = self.x
        self.Rect.centery = self.y
        pygame.draw.rect(screen, BLUE, self.Rect)


particles = []

done = False
while not done:

    screen.fill(WHITE)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True


        if pygame.mouse.get_pressed()[0]:
            mousex = pygame.mouse.get_pos()[0]
            mousey = pygame.mouse.get_pos()[1]

            theta = math.degrees(math.atan(player_rect.x - mousey/  player_rect.y - mousex))
            dx = math.cos(theta) 
            dy = math.sin(theta)
            particles.append(Particle(dx, dy, player_rect.x, player_rect.y))

    for particle in particles:
        particle.draw(screen)



    player_rect = pygame.Rect(100, 150, 10, 10)
    pygame.draw.rect(screen, RED, player_rect)
    clock.tick(FPS)
    pygame.display.update()
pygame.quit()

解决方案

There is no need to compute the angle. Just compute the normalized direction (Unit vector):

dx, dy = mousex - player_rect.centerx, mousey - player_rect.centery
len = math.hypot(dx, dy)
if len > 0:
    particles.append(Particle(dx/len, dy/len, player_rect.centerx, player_rect.centery))

The center of the rectangle is player_rect.centerx, player_rect.centery respectively player_rect.center rather than player_rect.x, player_rect.y.

---

Complete example:

import pygame
import math

FPS = 60
WHITE = (255, 255, 255)
RED = (255, 0, 0)
BLUE = (0, 0, 255)

pygame.init()
screen = pygame.display.set_mode([300, 300])
clock = pygame.time.Clock()

class Particle:
    def __init__(self, dx, dy, x, y):
        self.dx = dx
        self.dy = dy
        self.x = x
        self.y = y
        self.Rect = pygame.Rect(100, 150, 5, 5)

    def draw(self, screen):
        self.x += self.dx
        self.y += self.dy
        self.Rect.centerx = self.x
        self.Rect.centery = self.y
        pygame.draw.rect(screen, BLUE, self.Rect)

particles = []

done = False
while not done:
    screen.fill(WHITE)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            done = True

        if pygame.mouse.get_pressed()[0]:
            mousex = pygame.mouse.get_pos()[0]
            mousey = pygame.mouse.get_pos()[1]

            dx, dy = mousex - player_rect.centerx, mousey - player_rect.centery
            len = math.hypot(dx, dy)
            if len > 0:
                particles.append(Particle(dx/len, dy/len, *player_rect.center))

    for particle in particles:
        particle.draw(screen)

    player_rect = pygame.Rect(100, 150, 10, 10)
    pygame.draw.rect(screen, RED, player_rect)
    pygame.display.flip()
    clock.tick(FPS)

pygame.quit()

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