[Python] Object moves a little bit weird with pygame vector2

I have an issue with pygame module. I have a small program where user can click on any place in a window and a ball will spawn there and start moving up-left with 45 degrees angle (135 actually) and everything seems pretty fine but if you spawn many of this orbs so they move like a beam you'll notice that they reflect not actually 90 degrees everytime. I mean, reflection isn't random, it's calculated, but direction of 45 degrees is obviously closer to 90 than it should be. You'll see what I mean if you start the program. So here is the code:

import math
import pygame

NE = 45
NW = 135
SW = 225
SE = 315
V = 5
TICK = 60
RADIUS = 10


def convert_degrees_to_radians(angle_degrees):
return math.radians(angle_degrees)


class Circle:

def __init__(self, center_pos, direction_angle):
self.center_pos = center_pos
self.movement_angle, self.movement_direction = None, None
self.change_direction(direction_angle)

def change_direction(self, new_angle):
self.movement_angle = new_angle
self.movement_direction = pygame.math.Vector2(math.cos(convert_degrees_to_radians(new_angle)),
math.sin(convert_degrees_to_radians(new_angle)))

def change_position(self, new_position):
self.center_pos = new_position


def draw_circle(position):
pygame.draw.circle(screen, pygame.Color('white'), position, RADIUS)


if __name__ == '__main__':
pygame.init()
pygame.display.set_caption('Balls')
size = width, height = 1000, 600
screen = pygame.display.set_mode(size)

running = True
circles = []
clock = pygame.time.Clock()
while running:
for event in pygame.event.get():
if event.type == pygame.QUIT:
running = False
if event.type == pygame.MOUSEBUTTONUP and event.button == 1:
draw_circle(event.pos)
circles.append(Circle(event.pos, NW))
screen.fill(pygame.Color('black'))
clock.tick(TICK)
for circle in circles:
new_center_pos = [int(circle.center_pos[0] + V * circle.movement_direction.x),
int(circle.center_pos[1] - V * circle.movement_direction.y)]
circle.change_position(tuple(new_center_pos))
draw_circle(circle.center_pos)
if circle.center_pos[0] <= RADIUS:
if circle.movement_angle == SW:
circle.change_direction(SE)
if circle.movement_angle == NW:
circle.change_direction(NE)
if circle.center_pos[0] >= width - RADIUS:
if circle.movement_angle == SE:
circle.change_direction(SW)
if circle.movement_angle == NE:
circle.change_direction(NW)
if circle.center_pos[1] <= RADIUS:
if circle.movement_angle == NW:
circle.change_direction(SW)
if circle.movement_angle == NE:
circle.change_direction(SE)
if circle.center_pos[1] >= height - RADIUS:
if circle.movement_angle == SW:
circle.change_direction(NW)
if circle.movement_angle == SE:
circle.change_direction(NE)
pygame.display.flip()
pygame.quit()



Does someone have an idea how to solve it? I tried, but really can't see any mistake.

I tried to calculate directions by myself instead of using degrees, but result was the same, so maybe there is a problem with calculations of new_center_pos but I can't see it.

Continue reading...