Transmission_line_animation_open_short2.gif (300 × 110 pixel, dimensione del file: 105 KB, tipo MIME: image/gif, ciclico, 50 frame, 2,5 s)
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Dettagli
DescrizioneTransmission line animation open short2.gif |
English: Two transmission lines, the top one terminated at an open-circuit, the bottom terminated at a short circuit. Black dots represent electrons, and the arrows show the electric field. |
Data | |
Fonte | Opera propria |
Autore | Sbyrnes321 |
Licenza
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Questo file è reso disponibile nei termini della licenza Creative Commons CC0 1.0 Universal. |
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Source code
"""
(C) Steven Byrnes, 2014-2016. This code is released under the MIT license
http://opensource.org/licenses/MIT
This code runs in Python 2.7 or 3.3. It requires imagemagick to be installed;
that's how it assembles images into animated GIFs.
"""
# Use Python 3 style division: a/b is real division, a//b is integer division
from __future__ import division
import subprocess, os
directory_now = os.path.dirname(os.path.realpath(__file__))
import pygame as pg
from numpy import pi, linspace, cos, sin
frames_in_anim = 50
animation_loop_seconds = 2.5 #time in seconds for animation to loop one cycle
bgcolor = (255,255,255) #background is white
ecolor = (0,0,0) #electrons are black
wire_color = (200,200,200) # wire color is light gray
split_line_color = (0,0,0) #line down the middle is black
arrow_color = (140,0,0) #arrows are red
# pygame draws pixel-art, not smoothed. Therefore I am drawing it
# bigger, then smoothly shrinking it down
img_height = 330
img_width = 900
final_height = 110
final_width = 300
# ~23 megapixel limit for wikipedia animated gifs
assert final_height * final_width * frames_in_anim < 22e6
# transmission line wire length and thickness, and y-coordinate of the top of
# each wire
tl_length = int(img_width * .9)
tl_thickness = 27
tl_open_top_y = 30
tl_open_bot_y = tl_open_top_y + 69
tl_short_top_y = 204
tl_short_bot_y = tl_short_top_y + 69
tl_open_center_y = int((tl_open_top_y + tl_open_bot_y + tl_thickness) / 2)
tl_short_center_y = int((tl_short_top_y + tl_short_bot_y + tl_thickness) / 2)
wavelength = 1.1 * tl_length
e_radius = 4
# dimensions of triangular arrow head (this is for the longest arrows; it's
# scaled down when the arrow is too small)
arrowhead_base = 9
arrowhead_height = 15
# width of the arrow line
arrow_width = 6
# number of electrons spread out over the transmission line (top plus bottom)
num_electrons = 100
# max_e_displacement is defined here as a multiple of the total electron path length
# (roughly twice the width of the image, because we're adding top + bottom)
max_e_displacement = 1/40
num_arrows = 20
max_arrow_halflength = 18
def tup_round(tup):
"""round each element of a tuple to nearest integer"""
return tuple(int(round(x)) for x in tup)
def draw_arrow(surf, x, tail_y, head_y):
"""
draw a vertical arrow. Coordinates do not need to be integers
"""
# calculate dimensions of the triangle; it's scaled down for short arrows
if abs(head_y - tail_y) >= 1.5 * arrowhead_height:
h = arrowhead_height
b = arrowhead_base
else:
h = abs(head_y - tail_y) / 1.5
b = arrowhead_base * h / arrowhead_height
if tail_y < head_y:
# downward arrow
triangle = [tup_round((x, head_y)),
tup_round((x - b, head_y - h)),
tup_round((x + b, head_y - h))]
triangle_middle_y = head_y - h/2
else:
# upward arrow
triangle = [tup_round((x, head_y)),
tup_round((x - b, head_y + h)),
tup_round((x + b, head_y + h))]
triangle_middle_y = head_y + h/2
pg.draw.line(surf, arrow_color, tup_round((x, tail_y)),
tup_round((x, triangle_middle_y)), arrow_width)
pg.draw.polygon(surf, arrow_color, triangle, 0)
def e_path_open(param, time):
"""
"param" is an abstract coordinate that goes from 0 to 1 as the electron
position goes right across the top wire then left across the bottom wire.
"time" goes from 0 to 2pi over the course of the animation.
This returns a dictionary: 'pos' is (x,y), the
coordinates of the corresponding point on the electron
dot path; 'displacement' is the displacement of an electron at this point
relative to its equilibrium position (between -1 and -1); and 'charge' is
the net charge at this point (between -1 and +1)
This is for the open-circuit line.
"""
# d is a vertical offset between the electrons and the wires
d = e_radius + 2
# pad is how far to extend the transmission line beyond the image borders
# (since those electrons may enter the image a bit)
pad = 36
path_length = 2 * (tl_length + pad)
howfar = param * path_length
#go right along top transmission line
if howfar < tl_length + pad:
x = howfar - pad
y = tl_open_top_y + tl_thickness - d
displacement = -sin(2 * pi * (tl_length - x) / wavelength) * cos(time)
charge = cos(2 * pi * (tl_length - x) / wavelength) * cos(time)
return {'pos':(x,y), 'displacement': displacement, 'charge': charge}
#go left along bottom transmission line
x = path_length - howfar - pad
y = tl_open_bot_y + d
displacement = -sin(2 * pi * (tl_length - x) / wavelength) * cos(time)
charge = -cos(2 * pi * (tl_length - x) / wavelength) * cos(time)
return {'pos':(x,y), 'displacement': displacement, 'charge': charge}
def e_path_short(param, time):
"""Same as e_path_open(...) above, but for the short-circuit line."""
# d is a vertical offset between the electrons and the wires
d = e_radius + 2
# pad is how far to extend the transmission line beyond the image borders
# (since those electrons may enter the image a bit)
pad = 36
path_length = (2 * (tl_length + pad) + 4*d
+ (tl_short_bot_y - tl_short_top_y - tl_thickness))
howfar = param * path_length
#at the beginning, go right along top wire
if howfar < tl_length + pad:
x = howfar - pad
y = tl_short_top_y + tl_thickness - d
displacement = cos(2 * pi * (tl_length - x) / wavelength) * cos(time)
charge = sin(2 * pi * (tl_length - x) / wavelength) * cos(time)
return {'pos':(x,y), 'displacement': displacement, 'charge': charge}
#at the end, go left along bottom wire
if (path_length - howfar) < tl_length + pad:
x = path_length - howfar - pad
y = tl_short_bot_y + d
displacement = cos(2 * pi * (tl_length - x) / wavelength) * cos(time)
charge = -sin(2 * pi * (tl_length - x) / wavelength) * cos(time)
return {'pos':(x,y), 'displacement': displacement, 'charge': charge}
#in the middle...
charge = 0
displacement = cos(time)
#top part of short...
if tl_length + pad < howfar < tl_length + pad + d:
x = howfar - pad
y = tl_short_top_y + tl_thickness - d
#bottom part of short...
elif tl_length + pad < (path_length - howfar) < tl_length + pad + d:
x = path_length - howfar - pad
y = tl_short_bot_y + d
#vertical part of short...
else:
x = tl_length + d
y = (tl_short_top_y + tl_thickness - d) + ((howfar-pad) - (tl_length + d))
return {'pos': (x,y), 'displacement': displacement, 'charge': charge}
def e_path(param, time, which):
return e_path_open(param, time) if which == 'open' else e_path_short(param, time)
def main():
#Make and save a drawing for each frame
filename_list = [os.path.join(directory_now, 'temp' + str(n) + '.png')
for n in range(frames_in_anim)]
for frame in range(frames_in_anim):
time = 2 * pi * frame / frames_in_anim
#initialize surface
surf = pg.Surface((img_width,img_height))
surf.fill(bgcolor);
#draw transmission line
pg.draw.rect(surf, wire_color, [0, tl_open_top_y, tl_length, tl_thickness])
pg.draw.rect(surf, wire_color, [0, tl_open_bot_y, tl_length, tl_thickness])
pg.draw.rect(surf, wire_color, [0, tl_short_top_y, tl_length, tl_thickness])
pg.draw.rect(surf, wire_color, [0, tl_short_bot_y, tl_length, tl_thickness])
pg.draw.rect(surf, wire_color, [tl_length,
tl_short_top_y,
tl_thickness,
tl_short_bot_y - tl_short_top_y + tl_thickness])
#draw line down the middle
pg.draw.line(surf,split_line_color, (0,img_height//2),
(img_width,img_height//2), 12)
#draw electrons. Remember, "param" is an abstract coordinate that goes
#from 0 to 1 as the electron position goes right across the top wire
#then left across the bottom wire
equilibrium_params = linspace(0, 1, num=num_electrons)
for which in ['open', 'short']:
for eq_param in equilibrium_params:
temp = e_path(eq_param, time, which)
param_now = eq_param + max_e_displacement * temp['displacement']
xy_now = e_path(param_now, time, which)['pos']
pg.draw.circle(surf, ecolor, tup_round(xy_now), e_radius)
#draw arrows
arrow_params = linspace(0, 0.49, num=num_arrows)
for which in ['open', 'short']:
center_y = tl_open_center_y if which == 'open' else tl_short_center_y
for i in range(len(arrow_params)):
a = arrow_params[i]
arrow_x = e_path(a, time, which)['pos'][0]
charge = e_path(a, time, which)['charge']
head_y = center_y + max_arrow_halflength * charge
tail_y = center_y - max_arrow_halflength * charge
draw_arrow(surf, arrow_x, tail_y, head_y)
#shrink the surface to its final size, and save it
shrunk_surface = pg.transform.smoothscale(surf, (final_width, final_height))
pg.image.save(shrunk_surface, filename_list[frame])
seconds_per_frame = animation_loop_seconds / frames_in_anim
frame_delay = str(int(seconds_per_frame * 100))
# Use the "convert" command (part of ImageMagick) to build the animation
command_list = ['convert', '-delay', frame_delay, '-loop', '0'] + filename_list + ['anim.gif']
subprocess.call(command_list, cwd=directory_now)
# Earlier, we saved an image file for each frame of the animation. Now
# that the animation is assembled, we can (optionally) delete those files
if True:
for filename in filename_list:
os.remove(filename)
main()
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11 nov 2014
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Data/Ora | Miniatura | Dimensioni | Utente | Commento | |
---|---|---|---|---|---|
attuale | 04:10, 29 mag 2016 | ![]() | 300 × 110 (105 KB) | Sbyrnes321 | all arrows are now red, to reduce image complexity |
06:12, 12 nov 2014 | ![]() | 300 × 110 (155 KB) | Sbyrnes321 | User created page with UploadWizard |
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