How to detect that two bodies (in my case, balls) have touched while they are moving?

Question

I’m doing a program in python that simulates a small game of billiards (pool) and I’m having trouble finding a simple way to identify when the two balls touch, so I can change their direction. My code can be found at: https://py3.codeskulptor.org/#user304_IhC0l87Ss8kkIU2.py My code is like this:

import simplegui

# inicializa as variáveis globais
LARGURA = 600
ALTURA = 400
RAIO_BOLA = 20

#posições das bolas
ball_pos = [LARGURA / 3, ALTURA / 2]
ball_pos2 = [LARGURA - (RAIO_BOLA * 2) + 5, ALTURA / 2]

#velocidade das bolas
vel = [2, 2]
vel2 = [2, 2]

# define os event handlers
def draw(canvas):

    global ball_pos, vel,  ball_pos2, vel2

    # Atualiza a pisição da bola1
    ball_pos[0] = ball_pos[0] + vel[0]
    ball_pos[1] = ball_pos[1] + vel[1]

    # Atualiza a pisição da bola2
    ball_pos2[0] = ball_pos2[0] + vel2[0]
    ball_pos2[1] = ball_pos2[1] + vel2[1]

    reflexaoBola1() 
    reflexaoBola2()

    # Desenha as bolas
    canvas.draw_circle(ball_pos, RAIO_BOLA, 2, "white", "White")
    canvas.draw_circle(ball_pos2, RAIO_BOLA, 2, "blue", "blue")


def reflexaoBola1():
    global ball_pos, vel, ball_pos2, vel2

    # Reflexão com a parede a direita
    if ball_pos[0] > LARGURA - RAIO_BOLA:
        vel[0] = -1 * vel[0]

    # Reflexão com a parede a esquerda
    if ball_pos[0] < RAIO_BOLA:
        vel[0] = -1 * vel[0]

    # Reflexão com a parede em cima
    if ball_pos[1] > ALTURA - RAIO_BOLA:
        vel[1] = -1 * vel[1]

    # Reflexão com a parede em baixo
    if ball_pos[1] < RAIO_BOLA:
        vel[1] = -1 * vel[1]


def reflexaoBola2():
    global ball_pos, vel, ball_pos2, vel2

    # Reflexão com a parede a direita
    if ball_pos2[0] > LARGURA - RAIO_BOLA:
        vel2[0] = -1 * vel2[0]

    # Reflexão com a parede a esquerda
    if ball_pos2[0] < RAIO_BOLA:
        vel2[0] = -1 * vel2[0]

    # Reflexão com a parede em cima
    if ball_pos2[1] > ALTURA - RAIO_BOLA:
        vel2[1] = -1 * vel2[1]

    # Reflexão com a parede em baixo
    if ball_pos2[1] < RAIO_BOLA:
        vel2[1] = -1 * vel2[1]


# cria o frame
frame = simplegui.create_frame("Motion", LARGURA, ALTURA)

# registra os event handlers
frame.set_draw_handler(draw)

# inicia frame
frame.start()

If you rotate my code, you will see that the balls only collide with the walls instead of colliding with each other, I would like to solve that part

Answer 1

Hello viva uses so although this solution only reflect the change of direction on the X axis, you can change how you want it to be, however with this function that I share will stop colliding as you wanted.

Flames this function in DRAW

def reflexaoEntreBolas():
    if (ball_pos2[0] - (RAIO_BOLA * 2)) <= ball_pos[0] <= (ball_pos2[0] + (RAIO_BOLA * 2)) and (ball_pos2[1] - (RAIO_BOLA * 2)) <= ball_pos[1] <= (ball_pos2[1] + (RAIO_BOLA * 2)):
        vel[0] = -1 * vel[0]
        vel2[0] = -1 * vel2[0]