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pythonpygamemask

python pygame mask collision

when I try to use this piece of code, it only works for 1 object, not for every. I'm trying to modify code from this video (https://www.youtube.com/watch?v=Idu8XfwKUao). Is there is a simpler way to get a result ?.If there is,please let me know

#part of code that doesn't matter
randomx = [100,400,300]
randomy = [100,0,300]
green_blob = pygame.image.load("greenblob-59x51.png").convert_alpha()
orange_blob = pygame.image.load("orangeblob-59x51.png").convert_alpha()
blob_mask = pygame.mask.from_surface(green_blob)
blob_color = green_blob
obstacle = []
obstacle_mask = []
oy = []
ox = []
for i in range(4):
    obstacle.append(pygame.image.load("obstacle-400x399.png").convert_alpha())
    obstacle_mask.append(pygame.mask.from_surface(obstacle[i]))
    ox.append(random.choice(randomx))
    oy.append(random.choice(randomy))
# main loop
while True:
    events()
    for i in range(4):
        mx, my = pygame.mouse.get_pos()

        offset = ((mx - int(ox[i]))), ((my - int(oy[i])))
        result = obstacle_mask[i].overlap(blob_mask, offset)
        if result:
            blob_color = orange_blob
        else:
            blob_color = green_blob
        screen.blit(obstacle[i], (ox[i], oy[i]))
        screen.blit(blob_color, (mx, my))



    pygame.display.update()
    CLOCK.tick(FPS)
    screen.fill(BLACK)
Solution

  • Your application works fine. The issue is, that result of each evaluation of overlap cause a change of blob_color. So the last obstacle in the loop "wins". If the last obstacle overlaps the blob, then the color is orange_blob, else it is green_blob.
    Set the green color before the loop. If any obstacle overlaps the blob, then change it to orange. The blob has to be drawn once after the loop. e.g.:

    while True:
    events()

    blob_color = green_blob
    for i in range(4):
        mx, my = pygame.mouse.get_pos()

        offset = (int(mx - ox[i]), int(my - oy[i]))
        if obstacle_mask[i].overlap(blob_mask, offset):
            blob_color = orange_blob

        screen.blit(obstacle[i], (ox[i], oy[i]))

    screen.blit(blob_color, (mx, my))

    To find obstacle at random positions, which are not overlapping, you have to evaluate if a new obstacle hits any of the former obstacles.
    Create a random position:

    x, y = random.randint(100, 400), random.randint(100, 400)

    And evaluate if there is any obstacle that overlaps the new position.

    isect = any(obstacle_mask[j].overlap(obstacle_mask[i], (x-ox[j], y-oy[j])) for j in range(i))

    If that is the case, then repeat the process. Create a new random position and test for overlapping: 

    obstacle = []
obstacle_mask = []
oy = []
ox = []
for i in range(4):
    obstacle.append(pygame.image.load("obstacle-400x399.png").convert_alpha())
    obstacle_mask.append(pygame.mask.from_surface(obstacle[i]))

    isect = True
    while isect:
        x, y = random.randint(100, 400), random.randint(100, 400)
        isect = any(obstacle_mask[j].overlap(obstacle_mask[i], (x-ox[j], y-oy[j])) for j in range(i))

    ox.append(x)
    oy.append(y)