How do I gently change the direction of movement when moving forward?

Question

I drive a car using the key buttons. It works too. I would like in addition, when the car is at a standstill, turn the wheels without the car turning. If I then drive forwards / backwards, the car should start moving in the direction of the turned wheels. Like in real life. But in my code, the car is moving when i move the wheels.There is something wrong with the if Condition?

import pygame
import sys
import math
pygame.init()
cell_size = 40
cell_number = 20
breite = int(cell_size * cell_number )
hoehe  = int( cell_size * cell_number ) 
screen = pygame.display.set_mode((breite,hoehe))
clock = pygame.time.Clock()

class MyCar(pygame.sprite.Sprite):       
    def __init__(self,x,y):
        pygame.sprite.Sprite.__init__(self) 
        self.image = pygame.transform.scale(auto_img,(30,66))#.convert_alpha()  
        self.rect = self.image.get_rect()              
        self.rect.center = (x,y)            
        self.rect.x = x
        self.rect.y = y        
        self.driving_angle = 0
        self.speed = 5
        self.links = False
        self.rechts = False 
        self.vor = False 
        self.zurueck = False        
        self.steering_angle = 0      
       
    def update(self):  
        for event in events:
            if event.type == pygame.KEYDOWN:    
                if event.key == pygame.K_LEFT:                                 
                        self.links = True                        
                elif event.key == pygame.K_RIGHT:                      
                        self.rechts = True                        
                elif event.key == pygame.K_UP:
                        self.vor = True                       
                elif event.key == pygame.K_DOWN:
                        self.zurueck = True                                         
            elif event.type == pygame.KEYUP:        
                if event.key == pygame.K_LEFT:                  
                        self.links = False
                elif event.key == pygame.K_RIGHT:
                        self.rechts = False
                elif event.key == pygame.K_UP:
                        self.vor = False
                elif event.key == pygame.K_DOWN:
                        self.zurueck = False
        
        if self.vor or self.zurueck: 
            dx = math.cos(math.radians(self.driving_angle))
            dy = math.sin(math.radians(self.driving_angle)) 

        if self.vor:
            self.rect.y -= int(self.speed * dx)
            self.rect.x -= int(self.speed * dy)
        elif self.zurueck:       
            self.rect.y += int(self.speed * dx)
            self.rect.x += int(self.speed * dy)           
        if self.links:
            self.steering_angle -=1            
            self.steering_angle=min(self.steering_angle,120) 
        elif self.rechts:
            self.steering_angle +=-1            
            self.steering_angle=max(self.steering_angle,-120) 
        if self.rechts:                   
            self.driving_angle += self.steering_angle           
            while self.driving_angle < 0:
               self.driving_angle += 360
        elif self.links:                       
            self.driving_angle -= self.steering_angle           
            while self.driving_angle > 359:
                  self.driving_angle -= 360               
 
def blitRotateCenter(image, left, top, angle):
    rotated_image = pygame.transform.rotate(image, angle)
    new_rect = rotated_image.get_rect(center = image.get_rect(center = (left, top)).center)
    screen.blit(rotated_image, new_rect)
    return new_rect

auto_img = pygame.image.load("Bilder/car.png").convert_alpha() 
auto = MyCar(breite/2,hoehe-100)
auto_sprite = pygame.sprite.Group()
auto_sprite.add(auto)

while True:
    clock.tick(10)      
    events = pygame.event.get()
    for event in events:                     
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit() 
       
    auto.update()  
    new_auto_rect = blitRotateCenter(auto.image, *auto.rect.center, auto.driving_angle)     
    auto.rect=new_auto_rect    
    
    pygame.display.flip()

Rabbid76 · Answer 1 · 2021-12-31T11:42:03.827

You have to change steering_angle when you press LEFT and RIGHT. However you have to change driving_angle when you drive forward or backward:

class MyCar(pygame.sprite.Sprite):
    # [...]

    def update(self): 
        # [...]

        if self.vor:
            self.rect.y -= int(self.speed * dx)
            self.rect.x -= int(self.speed * dy)
        elif self.zurueck:       
            self.rect.y += int(self.speed * dx)
            self.rect.x += int(self.speed * dy)           
        if self.links:
            self.steering_angle += 0.1            
            self.steering_angle=min(self.steering_angle, 30) 
        elif self.rechts:
            self.steering_angle -= 0.1          
            self.steering_angle=max(self.steering_angle,-30) 
        if self.vor:                   
            self.driving_angle += self.steering_angle           
            while self.driving_angle < 0:
               self.driving_angle += 360
        elif self.zurueck:                       
            self.driving_angle -= self.steering_angle           
            while self.driving_angle > 359:
                  self.driving_angle -= 360

I suggest to use pygame.key.get_pressed() instead of the keyboard events:
(See How can I make a sprite move when key is held down)

class MyCar(pygame.sprite.Sprite):
    # [...]

    def update(self):  
        keys = pygame.key.get_pressed()
        move = keys[pygame.K_UP] - keys[pygame.K_DOWN]
        stear = keys[pygame.K_RIGHT] - keys[pygame.K_LEFT]
             
        self.steering_angle = max(-2, min(2, self.steering_angle - stear * 0.2))  

        self.rect.y -= int(math.cos(math.radians(self.driving_angle)) * move * self.speed)
        self.rect.x -= int(math.sin(math.radians(self.driving_angle)) * move * self.speed)
        self.driving_angle += (self.steering_angle * move) % 360

How do I gently change the direction of movement when moving forward?

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