mixster

#!/usr/bin/python
import sys, pygame
from pygame.locals import *
import math

class Point(object):
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

class Body(object):
    def __init__(self, mass=1, pos=(0, 0), vel=Point(0, 0), radius=0):
        self.pos = pos
        self.radius = radius
        self.acc = Point(0, 0)
        self.vel = vel
        self.mass = mass

    def move(self, dx, dy):
        self.pos.x += dx
        self.pos.y += dy

    def resetForce(self):
        self.acc = Point(0, 0)

    def applyForce(self, force):
        self.acc.x += force.x / self.mass
        self.acc.y += force.y / self.mass

    def update(self):
        self.vel.x += self.acc.x# * 10000
        self.vel.y += self.acc.y# * 10000
        self.move(self.vel.x, self.vel.y)

    def draw(self, screen, color=(0, 0, 0), width=1):
        pygame.draw.circle(screen, color, (int(self.pos.x), int(self.pos.y)), self.radius, width)

def getEvents():
    for event in pygame.event.get():
        if event.type == KEYDOWN:
            if event.key == K_UP:
                planetC.move(0, -5)
            if event.key == K_DOWN:
                planetC.move(0, 5)
            if event.key == K_LEFT:
                planetC.move(-5, 0)
            if event.key == K_RIGHT:
                planetC.move(5, 0)
            if event.key == ord('q'):
                return False
    return True

def getGravity(bodyA, bodyB):
    dx = bodyA.pos.x - bodyB.pos.x
    dy = bodyA.pos.y - bodyB.pos.y
    d = dx**2 + dy**2

    if d == 0:
        return Point(0, 0)
    else:
        f = ((6.673*(10**-11)) * bodyA.mass * bodyB.mass) / d
        a = math.atan2(dy, dx)
        fx = f * -math.cos(a)
        fy = f * -math.sin(a)

        #print('dx: ' + str(int(dx)) + '; dy: ' + str(int(dy)))
        #print('fx: ' + str(int(fx)) + '; fy: ' + str(int(fy)))
        #print('f:  ' + str(int(f))  + '; a:  ' + str(int(a * (math.pi/180.0))))

        return Point(fx, fy)

def invertForce(force):
    return Point(-force.x, -force.y)

pygame.init()
screen = pygame.display.set_mode((600, 400))
pygame.display.set_caption('Gravity simulator')
pygame.mouse.set_visible(0)

clock = pygame.time.Clock()
planetA = Body(10**8, Point(200, 200), Point(0, 0.065), 25)
planetB = Body(10**8, Point(400, 200), Point(0, -0.065), 25)
planetC = Body(5*10**9, Point(300, 200), Point(0, 0), 10)

running = True
while running:
    running = getEvents()
    for i in range(1, 500):
        planetA.resetForce()
        planetB.resetForce()
        planetC.resetForce()

        f = getGravity(planetA, planetB)
        planetA.applyForce(f)
        planetB.applyForce(invertForce(f))

        f = getGravity(planetC, planetA)
        planetC.applyForce(f)
        planetA.applyForce(invertForce(f))

        f = getGravity(planetC, planetB)
        planetC.applyForce(f)
        planetB.applyForce(invertForce(f))

        planetA.update()
        planetB.update()
        planetC.update()

    pygame.draw.rect(screen, (0, 0, 0), pygame.Rect(0, 0, 600, 400))
    planetA.draw(screen, (255, 0, 0), 5)
    planetB.draw(screen, (0, 255, 0), 5)
    planetC.draw(screen, (0, 0, 255), 3)

    clock.tick(15)
    pygame.display.flip()
print('Terminating')