def __init__(self, astronomical_object, initial_distance=1000):
'''
Initializes the FreeFallSimulation instance.
@precondition: none.
@postcondition: The instance is ready to use. You should
bind_to_root though before you use the object.
@param initial_distance: The initial distance of the falling
object in meters. Defaults to 1000m.
@param astronomical_object: The astronomical object the
falling_object will free fall toward.
'''
self._canvas = None
self._velocity = None
self._velocity_label = None
self.falling_object = \
CanvasedFallingObject(FreeFallSimulation.WIDTH,
FreeFallSimulation.FREE_FALL_HEIGHT,
initial_distance=initial_distance)
self.astronomical_object = astronomical_object
class FreeFallSimulation(object):
'''
A representation of a free fall Simulation.
Represents a free fall simulation for a single falling object and
astronomical object.
'''
'''The height of the Free Fall part of the canvas.'''
FREE_FALL_HEIGHT = 400
'''The height of the planet part of the canvas.'''
PLANET_IMG_HEIGHT = 150
'''The width of the entire canvas.'''
WIDTH = 150
def __init__(self, astronomical_object, initial_distance=1000):
'''
Initializes the FreeFallSimulation instance.
@precondition: none.
@postcondition: The instance is ready to use. You should
bind_to_root though before you use the object.
@param initial_distance: The initial distance of the falling
object in meters. Defaults to 1000m.
@param astronomical_object: The astronomical object the
falling_object will free fall toward.
'''
self._canvas = None
self._velocity = None
self._velocity_label = None
self.falling_object = \
CanvasedFallingObject(FreeFallSimulation.WIDTH,
FreeFallSimulation.FREE_FALL_HEIGHT,
initial_distance=initial_distance)
self.astronomical_object = astronomical_object
def _kaboom(self):
'''
Displays the kaboom image if it is not shown.
@precondition: none.
@postcondition: The kaboom image is displayed over the planet
image if it is not already there.
'''
if not self._kaboom_image.on_canvas():
height = FreeFallSimulation.FREE_FALL_HEIGHT
self._kaboom_image.add_to_canvas(self._canvas,
0,
height,
anchor=tkinter.NW)
def _unkaboom(self):
'''
Removes the kaboom image if it is not shown.
@precondition: none.
@postcondition: The kaboom image is removed over the planet
image if it is there.
'''
if self._kaboom_image.on_canvas():
self._kaboom_image.remove_from_canvas(self._canvas)
def bind_to_root(self, root, row, col):
'''
binds this instances canvas and labels to the given root and
sets them up.
@precondition: none.
@postcondition: A canvas object is place under the root widget
using a grid and is placed in col, row.
@param root: The root tkinter widget that this canvas will
attach to.
@param col: The column number in the root's grid where this
canvas should be place.
@param row: The row number in the root's grid where this
canvas should be placed.
'''
# Create a label with the astronomical object name.
self._label = tkinter.Label(root, text=self.astronomical_object.name)
self._label.grid(column=col, row=row, sticky=(tkinter.W, tkinter.E))
# Create the canvas and add it to the grid expanding to all
# four corners.
height = (FreeFallSimulation.FREE_FALL_HEIGHT +
FreeFallSimulation.PLANET_IMG_HEIGHT)
self._canvas = tkinter.Canvas(root,
width=FreeFallSimulation.WIDTH,
height=height,
bg='black')
self._canvas.grid(column=col,
row=row + 1,
sticky=(tkinter.N, tkinter.W, tkinter.E, tkinter.S))
self.falling_object.add_to_canvas(self._canvas)
# Add the planet image at the bottom
height = FreeFallSimulation.FREE_FALL_HEIGHT
self.astronomical_object.image.add_to_canvas(self._canvas,
0,
height,
anchor=tkinter.NW)
# Add a label for the gravitational force just below the
# canvas. We use a StringVar because it will update the label
# automatically.
self._g = tkinter.StringVar()
self._g.set("{0:.3f}".format(self.astronomical_object.gravity))
self._g_label = tkinter.Label(root, textvariable=self._g)
self._g_label.grid(column=col, row=row + 2,
sticky=(tkinter.N, tkinter.W, tkinter.E, tkinter.S))
# Add a label for the velocity just below the canvas. We use a
# StringVar because it will update the label automatically.
self._velocity = tkinter.StringVar()
self._velocity.set('0.0')
self._velocity_label = tkinter.Label(root, textvariable=self._velocity)
self._velocity_label.grid(column=col, row=row + 3,
sticky=(tkinter.N, tkinter.W,
tkinter.E, tkinter.S))
# Add a label for the time to land below the canvas. We use a
# StringVar because it will update the label automatically.
self._ttl = tkinter.StringVar()
self._ttl.set('0.0')
self._ttl_label = tkinter.Label(root, textvariable=self._ttl)
self._ttl_label.grid(column=col, row=row + 4,
sticky=(tkinter.N, tkinter.W,
tkinter.E, tkinter.S))
# Add a label for the distance to land below the canvas. We
# use a StringVar because it will update the label
# automatically.
self._d = tkinter.StringVar()
self._d.set('0.0')
self._d_label = tkinter.Label(root, textvariable=self._d)
self._d_label.grid(column=col, row=row + 5,
sticky=(tkinter.N, tkinter.W,
tkinter.E, tkinter.S))
self._kaboom_image = FreeFallCanvasImage('kaboom', 'kaboom.gif')
def move_falling_object(self, time=0):
'''
Move the falling object to the position at the specified time.
Moves the falling object to its proper position at the given
time and updates all the associated calculations.
@precondition: none.
@postcondition: The falling object is moved on the canvas to
its position at the given time and the other calculates are
updated to represent its new location.
@param time: The time in seconds to where the ball should be
moved.
@raise FreeFallException: If the canvas is not initialized,
this is thrown. Calling 'bind_to_root' first will solve this
problem.
'''
# We need a canvas to do anything.
if self._canvas is None:
from freefallsimulator import FreeFallException
raise FreeFallException("Tkinter objects not initialized. " +
"Call 'bind_to_root' first.")
if self.has_collided(time):
# If it's collided, set the time to 0. The resolution may not
# be sufficient to show an exact 0.
self._ttl.set('{0:.3f}'.format(float(0.0)))
self._d.set('{0:.3f}'.format(float(0.0)))
self._kaboom()
self.falling_object.remove_object()
else:
# Prepare some calculations for display.
g = self.astronomical_object.gravity
t = time
v = self.falling_object.calculate_velocity_at_time(gravity=g,
time=t)
t0 = self.falling_object.calculate_time_to_surface(gravity=g)
d = self.falling_object.calculate_distance_to_planet(time=t,
gravity=g)
# Move it.
self.falling_object.create_object()
self.falling_object.move_object(gravity=g, time=t)
self._velocity.set('{0:.3f}'.format(v))
self._ttl.set('{0:.3f}'.format(t0))
self._d.set('{0:.3f}'.format(d))
# We aren't at the end, so make sure we aren't displaying
# the kaboom.
self._unkaboom()
def has_collided(self, time=0):
'''
Determines if a collision has occurred at the given time.
@precondition: none.
@postcondition: none.
@param time: The time in seconds to where the ball should be
checked for a collision.
@return: True if a collision has occurred at or before the
given time, False otherwise.
'''
i = self.falling_object.initial_distance
g = self.astronomical_object.gravity
tts = self.falling_object.calculate_time_to_surface(distance=i,
gravity=g)
return tts <= time
