| | |
| | """ turtle-example-suite: |
| | |
| | tdemo_planets_and_moon.py |
| | |
| | Gravitational system simulation using the |
| | approximation method from Feynman-lectures, |
| | p.9-8, using turtlegraphics. |
| | |
| | Example: heavy central body, light planet, |
| | very light moon! |
| | Planet has a circular orbit, moon a stable |
| | orbit around the planet. |
| | |
| | You can hold the movement temporarily by |
| | pressing the left mouse button with the |
| | mouse over the scrollbar of the canvas. |
| | |
| | """ |
| | from turtle import Shape, Turtle, mainloop, Vec2D as Vec |
| |
|
| | G = 8 |
| |
|
| | class GravSys(object): |
| | def __init__(self): |
| | self.planets = [] |
| | self.t = 0 |
| | self.dt = 0.01 |
| | def init(self): |
| | for p in self.planets: |
| | p.init() |
| | def start(self): |
| | for i in range(10000): |
| | self.t += self.dt |
| | for p in self.planets: |
| | p.step() |
| |
|
| | class Star(Turtle): |
| | def __init__(self, m, x, v, gravSys, shape): |
| | Turtle.__init__(self, shape=shape) |
| | self.penup() |
| | self.m = m |
| | self.setpos(x) |
| | self.v = v |
| | gravSys.planets.append(self) |
| | self.gravSys = gravSys |
| | self.resizemode("user") |
| | self.pendown() |
| | def init(self): |
| | dt = self.gravSys.dt |
| | self.a = self.acc() |
| | self.v = self.v + 0.5*dt*self.a |
| | def acc(self): |
| | a = Vec(0,0) |
| | for planet in self.gravSys.planets: |
| | if planet != self: |
| | v = planet.pos()-self.pos() |
| | a += (G*planet.m/abs(v)**3)*v |
| | return a |
| | def step(self): |
| | dt = self.gravSys.dt |
| | self.setpos(self.pos() + dt*self.v) |
| | if self.gravSys.planets.index(self) != 0: |
| | self.setheading(self.towards(self.gravSys.planets[0])) |
| | self.a = self.acc() |
| | self.v = self.v + dt*self.a |
| |
|
| | |
| |
|
| | def main(): |
| | s = Turtle() |
| | s.reset() |
| | s.getscreen().tracer(0,0) |
| | s.ht() |
| | s.pu() |
| | s.fd(6) |
| | s.lt(90) |
| | s.begin_poly() |
| | s.circle(6, 180) |
| | s.end_poly() |
| | m1 = s.get_poly() |
| | s.begin_poly() |
| | s.circle(6,180) |
| | s.end_poly() |
| | m2 = s.get_poly() |
| |
|
| | planetshape = Shape("compound") |
| | planetshape.addcomponent(m1,"orange") |
| | planetshape.addcomponent(m2,"blue") |
| | s.getscreen().register_shape("planet", planetshape) |
| | s.getscreen().tracer(1,0) |
| |
|
| | |
| | gs = GravSys() |
| | sun = Star(1000000, Vec(0,0), Vec(0,-2.5), gs, "circle") |
| | sun.color("yellow") |
| | sun.shapesize(1.8) |
| | sun.pu() |
| | earth = Star(12500, Vec(210,0), Vec(0,195), gs, "planet") |
| | earth.pencolor("green") |
| | earth.shapesize(0.8) |
| | moon = Star(1, Vec(220,0), Vec(0,295), gs, "planet") |
| | moon.pencolor("blue") |
| | moon.shapesize(0.5) |
| | gs.init() |
| | gs.start() |
| | return "Done!" |
| |
|
| | if __name__ == '__main__': |
| | main() |
| | mainloop() |
| |
|
