Random non overlapping circles(with circle number controlled) in python and pygame

Question

I was writing the code for non overlapping random circles with different radii.I kind of got the deserved, but my 'if' statement that checks overlap or non overlap excludes a number of circles. So, I get lesser number of circles. Here's the code:

import pygame
import numpy as np

pygame.init()
display_width = 800
display_height = 500

black = [0, 0, 0]
white = [255, 255, 255]
red = [255, 0, 0]

display_surface = pygame.display.set_mode((display_width, display_height))
clock = pygame.time.Clock()
pygame.display.set_caption("Random Circle")


def circle(x, y, r):
    pygame.draw.circle(display_surface, red, (int(x), int(y)), int(r), 2)


def distance(x1, y1, x2, y2):
    dsq = (x1 - x2) ** 2 + (y1 - y2) ** 2
    d = np.sqrt(dsq)
    return d


n = 100

r = np.random.randint(10, 20, size=n)
x = np.random.randint(r, display_width - r, size=n)
y = np.random.randint(r, display_height - r, size=n)

display_surface.fill(black)

for i in range(len(r)):
    valid = True
    for j in range(len(r)):
        if i != j:
            d = distance(x[i], y[i], x[j], y[j])
            if d < r[i] + r[j]:
                valid = False

    if valid:

        circle(x[i], y[i], r[i])

    pygame.display.update()
    clock.tick(100)

exit = False
while not exit:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()

I saw an answer to a question here which does exactly what this code does( except it uses a class of circles which I didn't use). I sense that I have to use some kind of while loop which doesn't end until I get my desired number o circles. But I find difficulty in actually writing the code. Can anyone help?

Answer 1

Create a list of circles Each circle is a tuple with 3 components, the x and y coordinate and the radius. Append new circles as long the length of the list is less than n:

circle_list = []
while len(circle_list) < n:
    # [...]

Create a random position and radius:

r = random.randint(10, 20)
x = random.randint(r, display_width - r)
y = random.randint(r, display_height - r)

Evaluate if the circle intersects with a other circle wich is in the list:

collide = False
for x2, y2, r2 in circle_list:
    d = distance(x, y, x2, y2)
    if d < r + r2:
        collide = True
        break

Append the circle if it does not collide:

if not collide:
    circle_list.append((x, y, r))

---

Minimal example:

import random
import math
import pygame

def euclidean_distance(x1, y1, x2, y2):
    #return math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    return math.hypot((x1 - x2), (y1 - y2))

pygame.init()
window = pygame.display.set_mode((400, 400))
font50 = pygame.font.SysFont(None, 50)
clock = pygame.time.Clock()

pygame.time.delay(10000)

run = True
circle_list = []
while run:
    clock.tick(100)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    r = random.randint(10, 20)
    x = random.randint(10+r, window.get_width()- r-10)
    y = random.randint(10+r, window.get_height()-r-10)
    if not any((x2, y2, r2) for x2, y2, r2 in circle_list if euclidean_distance(x, y, x2, y2) < r + r2):
        circle_list.append((x, y, r))    

    window.fill((255, 255, 255))
    for x, y, r in circle_list:
        pygame.draw.circle(window, (0, 0, 0), (round(x), round(y)), int(r), 3)
    window.blit(font50.render(str(len(circle_list)), True, (255, 0, 0)), (10, 10))
    pygame.display.flip()
 
pygame.quit()
exit()