How to make an object move across an angle in pygame

user_17273991 0
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I want to move my enemy across the imaginary hypotenuse of a triangle in pygame from a start_x, start_y variable to a target_x, target_y, how would I do that? This is part of my utility file

def polar_to_rectangularD(degrees, hypotenuse=1.0, inverted_y=True):
    opp = math.sin(math.degrees(degrees))*hypotenuse
    adj = math.cos(math.degrees(degrees))*hypotenuse
    if inverted_y:
        opp = -opp
    return opp,adj

def angle_towardsD(start_x, start_y, target_x, target_y, inverted_y=True):
    opp = target_y - start_y
    adj = target_x - start_x
    if inverted_y:
        opp = -opp
    angle = math.atan2(opp, adj)
    return math.degrees(angle)

And this is a portion of what I attempted to do with it in my main

if wall_spawn == 1:               
    enemy_y = player_ymax + player_half_height + enemy_radius     
    enemy_direction = -1
    spawn_angle = utility.angle_towardsD((win_width/6),650,(win_width/2),-100)
    enemy_x_offset, enemy_y_offset = utility.polar_to_rectangularD(spawn_angle,1)
    enemy_y -= enemy_y_offset
    enemy_movement += enemy_x_offset
#enemy_movement is set to None
pygame python
1 Answers

You don't need to calculate the angle. Just calculate the vector from the enemy to the player. Scale the vector by the speed of the enemy and add it to the enemies position:

def move_enemy(start_x, start_y, target_x, target_y, spped):
    dx = target_x - start_x
    dy = target_y - start_y
    dist = math.hypot(dx, dy)
    if dist > 0:
        start_x += min(spped, dist) * dx / dist
        start_y += min(spped, dist) * dy / dist
    return start_x, start_y

Minimal example:

import pygame, math

pygame.init()
window = pygame.display.set_mode((400, 400))
clock = pygame.time.Clock()
player_x, player_y, player_vel = 100, 100, 5
enemy_x, enemy_y, enemy_vel = 300, 300, 3

def move_enemy(start_x, start_y, target_x, target_y, speed):
    dx = target_x - start_x
    dy = target_y - start_y
    dist = math.hypot(dx, dy)
    if dist > 0:
        start_x += min(speed, dist) * dx / dist
        start_y += min(speed, dist) * dy / dist
    return start_x, start_y


run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False          
        
    keys = pygame.key.get_pressed()
    player_x = max(10, min(390, player_x + player_vel * (keys[pygame.K_d] - keys[pygame.K_a])))
    player_y = max(10, min(390, player_y + player_vel * (keys[pygame.K_s] - keys[pygame.K_w])))

    enemy_x, enemy_y = move_enemy(enemy_x, enemy_y, player_x, player_y, enemy_vel)

    window.fill(0)
    pygame.draw.circle(window, (0, 128, 255), (player_x, player_y), 10)
    pygame.draw.circle(window, (255, 32, 32), (enemy_x, enemy_y), 10)
    pygame.display.flip()

pygame.quit()
exit()
user_55777650
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