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I am trying to make a platformer in pygame and I have come across an issue. I can easily make collisions for rectangles and squares but I can't do it for right angle triangles. Is it possible to even do this using pygame? I have thought about just removing one of the corners to do it but I am unaware of how to do this and can't find any useful information anywhere. one person suggested using smaller rectangular collisions to make the triangles collisions but this didn't give the desired effect. the following code was made by someone else but it is basically the same as mine, the only difference is mine has animations etc and I changed some of the numbers in the jumping physics etc

#! /usr/bin/python

import pygame
from pygame import *

WIN_WIDTH = 800
WIN_HEIGHT = 640
HALF_WIDTH = int(WIN_WIDTH / 2)
HALF_HEIGHT = int(WIN_HEIGHT / 2)

DISPLAY = (WIN_WIDTH, WIN_HEIGHT)
DEPTH = 32
FLAGS = 0
CAMERA_SLACK = 30

def main():
    global cameraX, cameraY
    pygame.init()
    screen = pygame.display.set_mode(DISPLAY, FLAGS, DEPTH)
    pygame.display.set_caption("Use arrows to move!")
    timer = pygame.time.Clock()

    up = down = left = right = running = False
    bg = Surface((32,72))
    bg.convert()
    bg.fill(Color("#000000"))
    entities = pygame.sprite.Group()
    player = Player(32, 32)
    platforms = []

    x = y = 0
    level = [
        "PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP",
        "P                                          P",
        "P                                          P",
        "P                                          P",
        "P                    PPPPPPPPPPP           P",
        "P                                          P",
        "P                                          P",
        "P                                          P",
        "P    PPPPPPPP                              P",
        "P                                          P",
        "P                          PPPPPPP         P",
        "P                 PPPPPP                   P",
        "P                                          P",
        "P         PPPPPPP                          P",
        "P                                          P",
        "P                     PPPPPP               P",
        "P                                          P",
        "P   PPPPPPPPPPP                            P",
        "P                                          P",
        "P                 PPPPPPPPPPP              P",
        "P                                          P",
        "P                                          P",
        "P                                          P",
        "P                                          P",
        "PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP",]
    # build the level
    for row in level:
        for col in row:
            if col == "P":
                p = Platform(x, y)
                platforms.append(p)
                entities.add(p)
            if col == "E":
                e = ExitBlock(x, y)
                platforms.append(e)
                entities.add(e)
            x += 32
        y += 32
        x = 0

    total_level_width  = len(level[0])*32
    total_level_height = len(level)*32
    camera = Camera(complex_camera, total_level_width, total_level_height)
    entities.add(player)

    while 1:
        timer.tick(60)

        for e in pygame.event.get():
            if e.type == QUIT: raise SystemExit, "QUIT"
            if e.type == KEYDOWN and e.key == K_ESCAPE:
                raise SystemExit, "ESCAPE"
            if e.type == KEYDOWN and e.key == K_UP:
                up = True
            if e.type == KEYDOWN and e.key == K_DOWN:
                down = True
            if e.type == KEYDOWN and e.key == K_LEFT:
                left = True
            if e.type == KEYDOWN and e.key == K_RIGHT:
                right = True
            if e.type == KEYDOWN and e.key == K_SPACE:
                running = True

            if e.type == KEYUP and e.key == K_UP:
                up = False
            if e.type == KEYUP and e.key == K_DOWN:
                down = False
            if e.type == KEYUP and e.key == K_RIGHT:
                right = False
            if e.type == KEYUP and e.key == K_LEFT:
                left = False

        # draw background
        for y in range(32):
            for x in range(32):
                screen.blit(bg, (x * 32, y * 32))

        camera.update(player)

        # update player, draw everything else
        player.update(up, down, left, right, running, platforms)
        for e in entities:
            screen.blit(e.image, camera.apply(e))

        pygame.display.update()

class Camera(object):
    def __init__(self, camera_func, width, height):
        self.camera_func = camera_func
        self.state = Rect(0, 0, width, height)

    def apply(self, target):
        return target.rect.move(self.state.topleft)

    def update(self, target):
        self.state = self.camera_func(self.state, target.rect)

def simple_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera
    return Rect(-l+HALF_WIDTH, -t+HALF_HEIGHT, w, h)

def complex_camera(camera, target_rect):
    l, t, _, _ = target_rect
    _, _, w, h = camera
    l, t, _, _ = -l+HALF_WIDTH, -t+HALF_HEIGHT, w, h

    l = min(0, l)                           # stop scrolling at the left edge
    l = max(-(camera.width-WIN_WIDTH), l)   # stop scrolling at the right edge
    t = max(-(camera.height-WIN_HEIGHT), t) # stop scrolling at the bottom
    t = min(0, t)                           # stop scrolling at the top
    return Rect(l, t, w, h)

class Entity(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)

class Player(Entity):
    def __init__(self, x, y):
        Entity.__init__(self)
        self.xvel = 0
        self.yvel = 0
        self.onGround = False
        self.image = Surface((32,72))
        self.image.fill(Color("#0000FF"))
        self.image.convert()
        self.rect = Rect(x, y, 32, 72)

    def update(self, up, down, left, right, running, platforms):
        if up:
            # only jump if on the ground
            if self.onGround: self.yvel -= 10
        if down:
            pass
        if running:
            self.xvel = 12
        if left:
            self.xvel = -8
        if right:
            self.xvel = 8
        if not self.onGround:
            # only accelerate with gravity if in the air
            self.yvel += 0.3
            # max falling speed
            if self.yvel > 100: self.yvel = 100
        if not(left or right):
            self.xvel = 0
        # increment in x direction
        self.rect.left += self.xvel
        # do x-axis collisions
        self.collide(self.xvel, 0, platforms)
        # increment in y direction
        self.rect.top += self.yvel
        # assuming we're in the air
        self.onGround = False;
        # do y-axis collisions
        self.collide(0, self.yvel, platforms)

    def collide(self, xvel, yvel, platforms):
        for p in platforms:
            if pygame.sprite.collide_rect(self, p):
                if isinstance(p, ExitBlock):
                    pygame.event.post(pygame.event.Event(QUIT))
                if xvel > 0:
                    self.rect.right = p.rect.left
                    print "collide right"
                if xvel < 0:
                    self.rect.left = p.rect.right
                    print "collide left"
                if yvel > 0:
                    self.rect.bottom = p.rect.top
                    self.onGround = True
                    self.yvel = 0
                if yvel < 0:
                    self.rect.top = p.rect.bottom


class Platform(Entity):
    def __init__(self, x, y):
        Entity.__init__(self)
        self.image = Surface((32, 32))
        self.image.convert()
        self.image.fill(Color("#DDDDDD"))
        self.rect = Rect(x, y, 32, 32)

    def update(self):
        pass

class ExitBlock(Platform):
    def __init__(self, x, y):
        Platform.__init__(self, x, y)
        self.image.fill(Color("#0033FF"))

if __name__ == "__main__":
    main()
1234USSR4321
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    Possible duplicate of [Detection of Triangle Collision in 2D Space](https://stackoverflow.com/questions/2778240/detection-of-triangle-collision-in-2d-space) – Will Da Silva Jun 01 '17 at 15:15
  • This question doesn't really have much to do with pygame. Just because pygame lacks built-in functions for triangle collision detection doesn't mean you can't program that collision detection yourself. – Will Da Silva Jun 01 '17 at 15:16
  • ok. how would I go about doing that with the code I am using? – 1234USSR4321 Jun 01 '17 at 15:20
  • also, the " Detection of Triangle Collision in 2D Space " is asking how to collide 2 triangles but I want to know how to collide a triangle and a rectangle. the code people suggested doesn't seem like it would do what I need it to do – 1234USSR4321 Jun 01 '17 at 15:31
  • Every collision related algorithm can easily be found with a quick google search. We aren't here to write your code for you. https://gamedev.stackexchange.com/questions/8326/triangle-rectangle-intersection-in-2d – Will Da Silva Jun 01 '17 at 15:47
  • sorry to waste your time. I wasnt asking for you to do the code for me when I said "how would I go about doing that", what I was asking is how would I go about making my own collision detection for triangles if my code is already using pygames built in collision for rectangles. the player has a rectangular collision and I want them to go up triangular slopes. the players collision uses pygames built in stuff so would I need to write my own collision for the player to make it work with my own triangle collision detection or would it be possible to keep the code I have and just add to it? – 1234USSR4321 Jun 01 '17 at 16:27

2 Answers2

1

It isn't possible to implement triangle collision with the pygame module methods. But search about Pylygon module.

verbalki
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0

So, if you want to make a triangle collision, you can use this

Require for your triangle to calculate collision:

  • 3 points's position
  • Area of the triangle

How to calculate the area

self.area = abs((self.points[1][0] - self.points[0][0]) * (self.points[2][1] - self.points[0][1]) - (self.points[2][0] - self.points[0][0]) * (self.points[1][1] - self.points[0][1]))

Note: this is not really the triangle, it just save a bit of time by not dividing by 2

How to do the collision

def collision(self, pos):
    area1 = abs((self.points[0][0] - pos[0]) * (self.points[1][1] - pos[1]) - (self.points[1][0] - pos[0]) * (self.points[0][1] - pos[1]))
    area2 = abs((self.points[1][0] - pos[0]) * (self.points[2][1] - pos[1]) - (self.points[2][0] - pos[0]) * (self.points[1][1] - pos[1]))
    area3 = abs((self.points[2][0] - pos[0]) * (self.points[0][1] - pos[1]) - (self.points[0][0] - pos[0]) * (self.points[2][1] - pos[1]))
    areatotal = (area1 + area2 + area3) / 2
    if areatotal == self.area:
        return True

So yeah, this's the tip, if you want to apply more kinds of stuff, check this:

http://www.jeffreythompson.org/collision-detection/tri-point.php

This also has the explanation so you can get to see it, I'm not very good at explaining

Kirro Smith
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