hmz007
36ed224bac
Signed-off-by: hmz007 <hmz007@gmail.com> Change-Id: Ib87fdbe7a0be7dc961af3500fe9ea4589a127f9f
113 lines
2.8 KiB
Python
Executable File
113 lines
2.8 KiB
Python
Executable File
#!/usr/bin/env python
|
|
""" 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
|
|
from time import sleep
|
|
|
|
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
|
|
|
|
## create compound yellow/blue turtleshape for planets
|
|
|
|
def main():
|
|
s = Turtle()
|
|
s.reset()
|
|
s.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.tracer(1,0)
|
|
|
|
## setup gravitational system
|
|
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()
|