Pygame polygon click detection

Question

Here is my problem: I am creating a game and I have a board made out of polygons (hexagons). I want to be able to click on the different tiles but I can't find a simple method. I understood how to detect a click on basic surfaces such as rectangle or pictures, but not with more complex shapes like hexagons. Is it possible to do so?

I first searched for a Pygame function close to this but I didn't find any. Then I searched for the sprites, and I think it is possible, but very long. And the last way I found was to simply detect the color. However I don't want to change the color of the tiles.

How can I detect a click on a polygon? (Hexagons specifically)

Answer 1

I am currently using PyGame to build a small RPG game project, and I can personally attest that there is no built-in way to do this, at least nothing that I could find in the documentation or forums. Which is obviously very annoying and took me a long time to figure out.

The way I solved it was by:

1. Having a game loop that detects all hardware inputs from the mouse or keyboard:

for event in pygame.event.get():

2. Checking if a particular event is a mouse click event:

if event.type == pygame.MOUSEBUTTONUP:

3. Getting the position on screen where the mouse clicked:

pygame.mouse.get_pos()

4. Checking if anything with a special "clickable" attribute is on the screen at that position, and doing appropriate actions. For example, if I wanted to check for a particular object to see if the cursor was over that object at the moment of the click, I would do:

if clickableObject.collidepoint(mousePosition):

Hopefully this helps!

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Edit: I reread your question and am now realizing you wanted to know specifically about polygon detection, rather than general shape detection. Apologies if I was not answering your specific question. You may want to use something like Box2D for anything more complicated than a rectangular collision area, but most polygons should just be a matter of doing some more math.

Answer 2

I just ran into this issue when creating a board using triangles, I simply wanted to highlight whichever triangle the mouse was hovering over. As such I figured out:

When drawing the polygons you can simultaneously use the collidepoint() function to get a bool from the mouse position.

e.g.

if pg.draw.polygon(screen, white, polygon, 1).collidepoint(pg.mouse.get_pos()):
    pg.draw.polygon(screen, white, polygon, 0)

Answer 3

First, I want to thank you for your answer. I tried a method using the first 3 steps you gave, it worked (approximately) but it was not so optimized. I couldn't figur how to create a clickableObject using polygons. Then I discovered the masks, and using a mask on a polygon picture worked with the .collidepoint(pos). I hope it will work for my 70 polygons on the screen, but it worked just fine for one...

In my case I was using hexagons and I admit it is a very regular shape, I just find it strange that we could not use the "normal method".

Thanks again, and I hope I will one day play your RPG Pygame game.

~Definity

Answer 4

You can use pygame and PIL. I have this code:

import pygame, PIL.Image
pygame.init()

info = pygame.display.Info()
root = pygame.Surface((info.current_w, info.current_h))

def isPolygonInCords(pos: list, cordsOfPolygon):
    global info, root
    pygame.draw.polygon(root, (255, 255, 0), cordsOfPolygon)
    a = pygame.image.tostring(root, 'RGB')

    b = PIL.Image.fromBytes('RGB', (info.current_w, info.current_h), a)

    try:
        return b.getpixel(pos) == (255, 255, 0)

    except:
        return None