pygame，简单的物理引擎，如何在平面之间保持点？

问题描述

| 我正在尝试用Pygame（Python）编写本教程，并且遇到关于在平面之间保持点的问题。 我的代码是：fiz2.py 向量类别：vector.py 如果在Pygame屏幕上移动鼠标，飞机将旋转。当飞机旋转时，点将通过飞机并向外移动。 我试图在每次迭代中固定点的位置，但是它们仍然通过了飞机。我不知道该在哪里固定他们的位置。 注意：我知道我的代码有点混乱，这是我的第一个2d程序，我真的很难适应Pygame的坐标平面和向量。解决此问题后，我将重新编写。 注意2：是的，我在教程中写了关于如何在平面之间保持点的注释，我了解他固定位置的方式，但是不知道如何（在代码中）实现它。 谢谢。     

解决方法

我看不出来看代码。我的猜测是时变的，导致不稳定。但是我无法验证数学是否正确。虽然，我有有用的信息： 向量 通过将向量用作类与列表/元组，可以简化代码。 （速度，加速度，位置）视为一个对象，请分别使用.x和.y值。

# example:
pos[0] += vel[0]
pos[1] += vel[1]

# vs
pos += vel

有一个仅python的实现：euclid.py您可以用来与vector.py进行比较。 或在openGL中使用NumPy [用于3d图形。 ]是一个流行的，成熟的库。 物理 （看来您想通过编写自己的物理学来学习），但请查看PyMunk 颜色 您可以使用：pygame.Color

import pygame
from pygame import Color
color = Color(\'white\')
color2 = Color(\'lightgray\')
color3 = Color(0,128,128)

碰撞 查看pygame.sprite。* collide和pygame.Rect。* collide pygame游戏循环与numpy vector \'s 我写的样板

\"\"\" Pygame boilerplate. <ninmonkey>2011/04
        pygame main Game() loop,and numpy for vector math.

note:
        this might not be the most effecient way to use numpy as vectors,but it\'s an intro.

        And this does not force fixed-timesteps. If you want a stable simulation,you need to use a fixed timestep.
        see: http://gafferongames.com/game-physics/fix-your-timestep/

Keys:
    ESC : exit
    Space : game_init()
\"\"\"

import pygame
from pygame.locals import * 
from pygame import Color,Rect

import numpy as np

def get_screen_size():
    \"\"\"return screen (width,height) tuple\"\"\"
    screen = pygame.display.get_surface()
    return screen.get_size()

class Actor():
    \"\"\"basic actor,moves randomly.

    members:
        loc = position vector
        velocity = velocity vector
        width,height        
    \"\"\"
    def __init__(self,loc=None,velocity=None):
        \"\"\"optional initial loc and velocity vectors\"\"\"
        self.width = 50
        self.height = 50

        # if loc or velocity are not set: use random
        if loc is None: self.rand_loc()
        else: self.loc = loc

        if velocity is None: self.rand_velocity()
        else: self.velocity = velocity

    def update(self):
        \"\"\"update movement\"\"\" 
        self.loc += self.velocity

    def rand_velocity(self):
        \"\"\"set a random vector,based on random direction. Using unit circle:        
                x = cos(deg) * speed
        \"\"\"
        rad = np.radians( np.random.randint(0,360) )
        speed = np.random.randint(1,15)
        x = np.cos(rad)
        y = np.sin(rad)
        velocity = np.array( [x,y])
        velocity *= speed
        self.velocity = velocity 

    def rand_loc(self):
        \"\"\"random location onscreen\"\"\"
        width,height = get_screen_size()
        x = np.random.randint(0,width)
        y = np.random.randint(0,height)
        self.loc = np.array([x,y])

    def is_onscreen(self):
        \"\"\"test is screen.colliderect(actor) true?\"\"\"
        x,y = self.loc
        w,h = get_screen_size()

        screen = Rect(0,w,h)
        actor = Rect(x,y,self.width,self.height)

        if screen.colliderect(actor): return True
        else: return False

class GameMain():
    \"\"\"game Main entry point. handles intialization of game and graphics.\"\"\"
    done = False
    debug = False
    color_gray = Color(\'lightgray\')

    def __init__(self,width=800,height=600,color_bg=None):
        \"\"\"Initialize PyGame\"\"\"        
        pygame.init()
        self.width,self.height = width,height
        self.screen = pygame.display.set_mode(( self.width,self.height ))
        pygame.display.set_caption( \"boilerplate : pygame\" )        

        self.clock = pygame.time.Clock()
        self.limit_fps = True
        self.limit_fps_max = 60  

        if color_bg is None: color_bg = Color(50,50,50)       
        self.color_bg = color_bg

        self.game_init()

    def game_init(self):
        \"\"\"new game/round\"\"\"
        self.actors = [Actor() for x in range(10)]

    def loop(self):
        \"\"\"Game() main loop\"\"\"
        while not self.done:
            self.handle_events()
            self.update()
            self.draw()

            if self.limit_fps: self.clock.tick( self.limit_fps_max )
            else: self.clock.tick()

    def update(self):        
        \"\"\"update actors,handle physics\"\"\"
        for a in self.actors:
            a.update()

            if not a.is_onscreen():
                a.rand_loc()

    def handle_events(self):
        \"\"\"handle regular events. \"\"\"        
        events = pygame.event.get()
        # kmods = pygame.key.get_mods() # key modifiers

        for event in events:
            if event.type == pygame.QUIT: sys.exit()
            elif event.type == KEYDOWN:
                if (event.key == K_ESCAPE): self.done = True
                elif (event.key == K_SPACE): self.game_init()

    def draw(self):
        \"\"\"render screen\"\"\"
        # clear screen
        self.screen.fill( self.color_bg )

        # Actor: draw
        for a in self.actors:
            x,y = a.loc
            w,h = a.width,a.height
            r = Rect(x,h)
            self.screen.fill(self.color_gray,r)

        # will call update on whole screen Or flip buffer.
        pygame.display.flip()

if __name__ == \'__main__\':
    g = GameMain()
    g.loop()