Benjamin Peterson | 90f5ba5 | 2010-03-11 22:53:45 +0000 | [diff] [blame] | 1 | #!/usr/bin/env python3 |
Martin v. Löwis | 97cf99f | 2008-06-10 04:44:07 +0000 | [diff] [blame] | 2 | """ turtle-example-suite: |
| 3 | |
| 4 | tdemo_planets_and_moon.py |
| 5 | |
| 6 | Gravitational system simulation using the |
| 7 | approximation method from Feynman-lectures, |
| 8 | p.9-8, using turtlegraphics. |
| 9 | |
| 10 | Example: heavy central body, light planet, |
| 11 | very light moon! |
| 12 | Planet has a circular orbit, moon a stable |
| 13 | orbit around the planet. |
| 14 | |
| 15 | You can hold the movement temporarily by pressing |
| 16 | the left mouse button with mouse over the |
| 17 | scrollbar of the canvas. |
| 18 | |
| 19 | """ |
Martin v. Löwis | 60ebb8b | 2008-09-21 07:32:10 +0000 | [diff] [blame] | 20 | from turtle import Shape, Turtle, mainloop, Vec2D as Vec |
Martin v. Löwis | 97cf99f | 2008-06-10 04:44:07 +0000 | [diff] [blame] | 21 | from time import sleep |
| 22 | |
| 23 | G = 8 |
| 24 | |
| 25 | class GravSys(object): |
| 26 | def __init__(self): |
| 27 | self.planets = [] |
| 28 | self.t = 0 |
| 29 | self.dt = 0.01 |
| 30 | def init(self): |
| 31 | for p in self.planets: |
| 32 | p.init() |
| 33 | def start(self): |
| 34 | for i in range(10000): |
| 35 | self.t += self.dt |
| 36 | for p in self.planets: |
| 37 | p.step() |
| 38 | |
| 39 | class Star(Turtle): |
| 40 | def __init__(self, m, x, v, gravSys, shape): |
| 41 | Turtle.__init__(self, shape=shape) |
| 42 | self.penup() |
| 43 | self.m = m |
| 44 | self.setpos(x) |
| 45 | self.v = v |
| 46 | gravSys.planets.append(self) |
| 47 | self.gravSys = gravSys |
| 48 | self.resizemode("user") |
| 49 | self.pendown() |
| 50 | def init(self): |
| 51 | dt = self.gravSys.dt |
| 52 | self.a = self.acc() |
| 53 | self.v = self.v + 0.5*dt*self.a |
| 54 | def acc(self): |
| 55 | a = Vec(0,0) |
| 56 | for planet in self.gravSys.planets: |
| 57 | if planet != self: |
| 58 | v = planet.pos()-self.pos() |
| 59 | a += (G*planet.m/abs(v)**3)*v |
| 60 | return a |
| 61 | def step(self): |
| 62 | dt = self.gravSys.dt |
| 63 | self.setpos(self.pos() + dt*self.v) |
| 64 | if self.gravSys.planets.index(self) != 0: |
| 65 | self.setheading(self.towards(self.gravSys.planets[0])) |
| 66 | self.a = self.acc() |
| 67 | self.v = self.v + dt*self.a |
| 68 | |
| 69 | ## create compound yellow/blue turtleshape for planets |
| 70 | |
| 71 | def main(): |
| 72 | s = Turtle() |
| 73 | s.reset() |
| 74 | s.getscreen().tracer(0,0) |
| 75 | s.ht() |
| 76 | s.pu() |
| 77 | s.fd(6) |
| 78 | s.lt(90) |
| 79 | s.begin_poly() |
| 80 | s.circle(6, 180) |
| 81 | s.end_poly() |
| 82 | m1 = s.get_poly() |
| 83 | s.begin_poly() |
| 84 | s.circle(6,180) |
| 85 | s.end_poly() |
| 86 | m2 = s.get_poly() |
| 87 | |
| 88 | planetshape = Shape("compound") |
| 89 | planetshape.addcomponent(m1,"orange") |
| 90 | planetshape.addcomponent(m2,"blue") |
| 91 | s.getscreen().register_shape("planet", planetshape) |
| 92 | s.getscreen().tracer(1,0) |
| 93 | |
| 94 | ## setup gravitational system |
| 95 | gs = GravSys() |
| 96 | sun = Star(1000000, Vec(0,0), Vec(0,-2.5), gs, "circle") |
| 97 | sun.color("yellow") |
| 98 | sun.shapesize(1.8) |
| 99 | sun.pu() |
| 100 | earth = Star(12500, Vec(210,0), Vec(0,195), gs, "planet") |
| 101 | earth.pencolor("green") |
| 102 | earth.shapesize(0.8) |
| 103 | moon = Star(1, Vec(220,0), Vec(0,295), gs, "planet") |
| 104 | moon.pencolor("blue") |
| 105 | moon.shapesize(0.5) |
| 106 | gs.init() |
| 107 | gs.start() |
| 108 | return "Done!" |
| 109 | |
| 110 | if __name__ == '__main__': |
| 111 | msg = main() |
| 112 | print(msg) |
| 113 | #mainloop() |