I wanted to add a PyGame Sprite based answer to this question. Implementing this sort of thing as a sprite makes it easier to use the PyGame collision functions. For example, any number of CarSprites could be made, but their collision checked against the player's CarSrpite in a single call to groupcollide().
This implementation uses PyGame.math.Vector2() for velocity and position. This allows for a fairly simple turning and speed model utilising the Vector2's polar co-ordinate function. Initially this gave weird and confusing result... until I realised the Vector2.from_polar() required the angle in degrees. (Not radians unlike just about every other programming language function that takes angles.)
When the sprite is initially created, the code will make a lot of pre-rotated images. This does the smoothest turning at around 1 per degree (360), but if memory-usage was a issue, it could also be much less.
Anyway, the code is fairly self-explanatory. It requires a car_128.png image, and a background texture image road_texture.png. Please comment any questions.
import pygame import math # Window size WINDOW_WIDTH = 600 WINDOW_HEIGHT = 600 WINDOW_SURFACE = pygame.HWSURFACE|pygame.DOUBLEBUF|pygame.RESIZABLE class CarSprite( pygame.sprite.Sprite ): """ Car Sprite with basic acceleration, turning, braking and reverse """ def __init__( self, car_image, x, y, rotations=360 ): """ A car Sprite which pre-rotates up to <rotations> lots of angled versions of the image. Depending on the sprite's heading-direction, the correctly angled image is chosen. The base car-image should be pointing North/Up. """ pygame.sprite.Sprite.__init__(self) # Pre-make all the rotated versions # This assumes the start-image is pointing up-screen # Operation must be done in degrees (not radians) self.rot_img = [] self.min_angle = ( 360 / rotations ) for i in range( rotations ): # This rotation has to match the angle in radians later # So offet the angle (0 degrees = "north") by 90° to be angled 0-radians (so 0 rad is "east") rotated_image = pygame.transform.rotozoom( car_image, 360-90-( i*self.min_angle ), 1 ) self.rot_img.append( rotated_image ) self.min_angle = math.radians( self.min_angle ) # don't need degrees anymore # define the image used self.image = self.rot_img[0] self.rect = self.image.get_rect() self.rect.center = ( x, y ) # movement self.reversing = False self.heading = 0 # pointing right (in radians) self.speed = 0 self.velocity = pygame.math.Vector2( 0, 0 ) self.position = pygame.math.Vector2( x, y ) def turn( self, angle_degrees ): """ Adjust the angle the car is heading, if this means using a different car-image, select that here too """ ### TODO: car shouldn't be able to turn while not moving self.heading += math.radians( angle_degrees ) # Decide which is the correct image to display image_index = int( self.heading / self.min_angle ) % len( self.rot_img ) # Only update the image if it's changed if ( self.image != self.rot_img[ image_index ] ): x,y = self.rect.center self.image = self.rot_img[ image_index ] self.rect = self.image.get_rect() self.rect.center = (x,y) def accelerate( self, amount ): """ Increase the speed either forward or reverse """ if ( not self.reversing ): self.speed += amount else: self.speed -= amount def brake( self ): """ Slow the car by half """ self.speed /= 2 if ( abs( self.speed ) < 0.1 ): self.speed = 0 def reverse( self ): """ Change forward/reverse, reset any speed to 0 """ self.speed = 0 self.reversing = not self.reversing def update( self ): """ Sprite update function, calcualtes any new position """ self.velocity.from_polar( ( self.speed, math.degrees( self.heading ) ) ) self.position += self.velocity self.rect.center = ( round(self.position[0]), round(self.position[1] ) ) ### initialisation pygame.init() pygame.mixer.init() window = pygame.display.set_mode( ( WINDOW_WIDTH, WINDOW_HEIGHT ), WINDOW_SURFACE ) pygame.display.set_caption("Car Steering") ### Bitmaps road_image = road_image = pygame.image.load( 'road_texture.png' ) background = pygame.transform.smoothscale( road_image, ( WINDOW_WIDTH, WINDOW_HEIGHT ) ) car_image = pygame.image.load( 'car_128.png' ).convert_alpha() ### Sprites black_car = CarSprite( car_image, WINDOW_WIDTH//2, WINDOW_HEIGHT//2 ) car_sprites = pygame.sprite.Group() #Single() car_sprites.add( black_car ) ### Main Loop clock = pygame.time.Clock() done = False while not done: # Handle user-input for event in pygame.event.get(): if ( event.type == pygame.QUIT ): done = True elif ( event.type == pygame.VIDEORESIZE ): WINDOW_WIDTH = event.w WINDOW_HEIGHT = event.h window = pygame.display.set_mode( ( WINDOW_WIDTH, WINDOW_HEIGHT ), WINDOW_SURFACE ) background = pygame.transform.smoothscale( road_image, ( WINDOW_WIDTH, WINDOW_HEIGHT ) ) elif ( event.type == pygame.MOUSEBUTTONUP ): # On mouse-click pass elif ( event.type == pygame.KEYUP ): if ( event.key == pygame.K_h ): print( 'meep-meep' ) elif ( event.key == pygame.K_r ): print( 'resersing' ) black_car.reverse() elif ( event.key == pygame.K_UP ): print( 'accelerate' ) black_car.accelerate( 0.5 ) elif ( event.key == pygame.K_DOWN ): print( 'brake' ) black_car.brake( ) # Continuous Movement keys keys = pygame.key.get_pressed() if ( keys[pygame.K_LEFT] ): black_car.turn( -1.8 ) # degrees if ( keys[pygame.K_RIGHT] ): black_car.turn( 1.8 ) # Update the car(s) car_sprites.update() # Update the window window.blit( background, ( 0, 0 ) ) # backgorund car_sprites.draw( window ) pygame.display.flip() # Clamp FPS clock.tick_busy_loop(60) pygame.quit()
car_128.png (Source: https://openclipart.org )
road_texture.png
