Files
manim/3b1b_projects/active/diffyq/part2/fourier_series.py

932 lines
26 KiB
Python

from manimlib.imports import *
# import scipy
class FourierCirclesScene(Scene):
CONFIG = {
"n_vectors": 10,
"big_radius": 2,
"colors": [
BLUE_D,
BLUE_C,
BLUE_E,
GREY_BROWN,
],
"circle_style": {
"stroke_width": 2,
},
"vector_config": {
"buff": 0,
"max_tip_length_to_length_ratio": 0.35,
"tip_length": 0.15,
"max_stroke_width_to_length_ratio": 10,
"stroke_width": 2,
},
"circle_config": {
"stroke_width": 1,
},
"base_frequency": 1,
"slow_factor": 0.25,
"center_point": ORIGIN,
"parametric_function_step_size": 0.001,
"drawn_path_color": YELLOW,
"drawn_path_stroke_width": 2,
}
def setup(self):
self.slow_factor_tracker = ValueTracker(
self.slow_factor
)
self.vector_clock = ValueTracker(0)
self.vector_clock.add_updater(
lambda m, dt: m.increment_value(
self.get_slow_factor() * dt
)
)
self.add(self.vector_clock)
def get_slow_factor(self):
return self.slow_factor_tracker.get_value()
def get_vector_time(self):
return self.vector_clock.get_value()
#
def get_freqs(self):
n = self.n_vectors
all_freqs = list(range(n // 2, -n // 2, -1))
all_freqs.sort(key=abs)
return all_freqs
def get_coefficients(self):
return [complex(0) for x in range(self.n_vectors)]
def get_color_iterator(self):
return it.cycle(self.colors)
def get_rotating_vectors(self, freqs=None, coefficients=None):
vectors = VGroup()
self.center_tracker = VectorizedPoint(self.center_point)
if freqs is None:
freqs = self.get_freqs()
if coefficients is None:
coefficients = self.get_coefficients()
last_vector = None
for freq, coefficient in zip(freqs, coefficients):
if last_vector:
center_func = last_vector.get_end
else:
center_func = self.center_tracker.get_location
vector = self.get_rotating_vector(
coefficient=coefficient,
freq=freq,
center_func=center_func,
)
vectors.add(vector)
last_vector = vector
return vectors
def get_rotating_vector(self, coefficient, freq, center_func):
vector = Vector(RIGHT, **self.vector_config)
vector.scale(abs(coefficient))
if abs(coefficient) == 0:
phase = 0
else:
phase = np.log(coefficient).imag
vector.rotate(phase, about_point=ORIGIN)
vector.freq = freq
vector.coefficient = coefficient
vector.center_func = center_func
vector.add_updater(self.update_vector)
return vector
def update_vector(self, vector, dt):
time = self.get_vector_time()
coef = vector.coefficient
freq = vector.freq
phase = np.log(coef).imag
vector.set_length(abs(coef))
vector.set_angle(phase + time * freq * TAU)
vector.shift(vector.center_func() - vector.get_start())
return vector
def get_circles(self, vectors):
return VGroup(*[
self.get_circle(
vector,
color=color
)
for vector, color in zip(
vectors,
self.get_color_iterator()
)
])
def get_circle(self, vector, color=BLUE):
circle = Circle(color=color, **self.circle_config)
circle.center_func = vector.get_start
circle.radius_func = vector.get_length
circle.add_updater(self.update_circle)
return circle
def update_circle(self, circle):
circle.set_width(2 * circle.radius_func())
circle.move_to(circle.center_func())
return circle
def get_vector_sum_path(self, vectors, color=YELLOW):
coefs = [v.coefficient for v in vectors]
freqs = [v.freq for v in vectors]
center = vectors[0].get_start()
path = ParametricFunction(
lambda t: center + reduce(op.add, [
complex_to_R3(
coef * np.exp(TAU * 1j * freq * t)
)
for coef, freq in zip(coefs, freqs)
]),
t_min=0,
t_max=1,
color=color,
step_size=self.parametric_function_step_size,
)
return path
# TODO, this should be a general animated mobect
def get_drawn_path_alpha(self):
return self.get_vector_time()
def get_drawn_path(self, vectors, stroke_width=None, **kwargs):
if stroke_width is None:
stroke_width = self.drawn_path_stroke_width
path = self.get_vector_sum_path(vectors, **kwargs)
broken_path = CurvesAsSubmobjects(path)
broken_path.curr_time = 0
def update_path(path, dt):
# alpha = path.curr_time * self.get_slow_factor()
alpha = self.get_drawn_path_alpha()
n_curves = len(path)
for a, sp in zip(np.linspace(0, 1, n_curves), path):
b = alpha - a
if b < 0:
width = 0
else:
width = stroke_width * (1 - (b % 1))
sp.set_stroke(width=width)
path.curr_time += dt
return path
broken_path.set_color(self.drawn_path_color)
broken_path.add_updater(update_path)
return broken_path
def get_y_component_wave(self,
vectors,
left_x=1,
color=PINK,
n_copies=2,
right_shift_rate=5):
path = self.get_vector_sum_path(vectors)
wave = ParametricFunction(
lambda t: op.add(
right_shift_rate * t * LEFT,
path.function(t)[1] * UP
),
t_min=path.t_min,
t_max=path.t_max,
color=color,
)
wave_copies = VGroup(*[
wave.copy()
for x in range(n_copies)
])
wave_copies.arrange(RIGHT, buff=0)
top_point = wave_copies.get_top()
wave.creation = ShowCreation(
wave,
run_time=(1 / self.get_slow_factor()),
rate_func=linear,
)
cycle_animation(wave.creation)
wave.add_updater(lambda m: m.shift(
(m.get_left()[0] - left_x) * LEFT
))
def update_wave_copies(wcs):
index = int(
wave.creation.total_time * self.get_slow_factor()
)
wcs[:index].match_style(wave)
wcs[index:].set_stroke(width=0)
wcs.next_to(wave, RIGHT, buff=0)
wcs.align_to(top_point, UP)
wave_copies.add_updater(update_wave_copies)
return VGroup(wave, wave_copies)
def get_wave_y_line(self, vectors, wave):
return DashedLine(
vectors[-1].get_end(),
wave[0].get_end(),
stroke_width=1,
dash_length=DEFAULT_DASH_LENGTH * 0.5,
)
# Computing Fourier series
# i.e. where all the math happens
def get_coefficients_of_path(self, path, n_samples=10000, freqs=None):
if freqs is None:
freqs = self.get_freqs()
dt = 1 / n_samples
ts = np.arange(0, 1, dt)
samples = np.array([
path.point_from_proportion(t)
for t in ts
])
samples -= self.center_point
complex_samples = samples[:, 0] + 1j * samples[:, 1]
result = []
for freq in freqs:
riemann_sum = np.array([
np.exp(-TAU * 1j * freq * t) * cs
for t, cs in zip(ts, complex_samples)
]).sum() * dt
result.append(riemann_sum)
return result
class FourierSeriesIntroBackground4(FourierCirclesScene):
CONFIG = {
"n_vectors": 4,
"center_point": 4 * LEFT,
"run_time": 30,
"big_radius": 1.5,
}
def construct(self):
circles = self.get_circles()
path = self.get_drawn_path(circles)
wave = self.get_y_component_wave(circles)
h_line = always_redraw(
lambda: self.get_wave_y_line(circles, wave)
)
# Why?
circles.update(-1 / self.camera.frame_rate)
#
self.add(circles, path, wave, h_line)
self.wait(self.run_time)
def get_ks(self):
return np.arange(1, 2 * self.n_vectors + 1, 2)
def get_freqs(self):
return self.base_frequency * self.get_ks()
def get_coefficients(self):
return self.big_radius / self.get_ks()
class FourierSeriesIntroBackground8(FourierSeriesIntroBackground4):
CONFIG = {
"n_vectors": 8,
}
class FourierSeriesIntroBackground12(FourierSeriesIntroBackground4):
CONFIG = {
"n_vectors": 12,
}
class FourierSeriesIntroBackground20(FourierSeriesIntroBackground4):
CONFIG = {
"n_vectors": 20,
}
class FourierOfPiSymbol(FourierCirclesScene):
CONFIG = {
"n_vectors": 51,
"center_point": ORIGIN,
"slow_factor": 0.1,
"n_cycles": 1,
"tex": "\\pi",
"start_drawn": False,
"max_circle_stroke_width": 1,
}
def construct(self):
self.add_vectors_circles_path()
for n in range(self.n_cycles):
self.run_one_cycle()
def add_vectors_circles_path(self):
path = self.get_path()
coefs = self.get_coefficients_of_path(path)
vectors = self.get_rotating_vectors(coefficients=coefs)
circles = self.get_circles(vectors)
self.set_decreasing_stroke_widths(circles)
# approx_path = self.get_vector_sum_path(circles)
drawn_path = self.get_drawn_path(vectors)
if self.start_drawn:
self.vector_clock.increment_value(1)
self.add(path)
self.add(vectors)
self.add(circles)
self.add(drawn_path)
self.vectors = vectors
self.circles = circles
self.path = path
self.drawn_path = drawn_path
def run_one_cycle(self):
time = 1 / self.slow_factor
self.wait(time)
def set_decreasing_stroke_widths(self, circles):
mcsw = self.max_circle_stroke_width
for k, circle in zip(it.count(1), circles):
circle.set_stroke(width=max(
# mcsw / np.sqrt(k),
mcsw / k,
mcsw,
))
return circles
def get_path(self):
tex_mob = TexMobject(self.tex)
tex_mob.set_height(6)
path = tex_mob.family_members_with_points()[0]
path.set_fill(opacity=0)
path.set_stroke(WHITE, 1)
return path
class FourierOfName(FourierOfPiSymbol, MovingCameraScene):
CONFIG = {
"n_vectors": 100,
"name_color": WHITE,
"name_text": "Abc",
"time_per_symbol": 5,
"slow_factor": 1 / 5,
"parametric_function_step_size": 0.01,
}
def construct(self):
name = TextMobject(self.name_text)
max_width = FRAME_WIDTH - 2
max_height = FRAME_HEIGHT - 2
name.set_width(max_width)
if name.get_height() > max_height:
name.set_height(max_height)
frame = self.camera.frame
frame.save_state()
vectors = VGroup(VectorizedPoint())
circles = VGroup(VectorizedPoint())
for path in name.family_members_with_points():
for subpath in path.get_subpaths():
sp_mob = VMobject()
sp_mob.set_points(subpath)
coefs = self.get_coefficients_of_path(sp_mob)
new_vectors = self.get_rotating_vectors(
coefficients=coefs
)
new_circles = self.get_circles(new_vectors)
self.set_decreasing_stroke_widths(new_circles)
drawn_path = self.get_drawn_path(new_vectors)
drawn_path.clear_updaters()
drawn_path.set_stroke(self.name_color, 3)
static_vectors = VMobject().become(new_vectors)
static_circles = VMobject().become(new_circles)
# static_circles = new_circles.deepcopy()
# static_vectors.clear_updaters()
# static_circles.clear_updaters()
self.play(
Transform(vectors, static_vectors, remover=True),
Transform(circles, static_circles, remover=True),
frame.set_height, 1.5 * name.get_height(),
frame.move_to, path,
)
self.add(new_vectors, new_circles)
self.vector_clock.set_value(0)
self.play(
ShowCreation(drawn_path),
rate_func=linear,
run_time=self.time_per_symbol
)
self.remove(new_vectors, new_circles)
self.add(static_vectors, static_circles)
vectors = static_vectors
circles = static_circles
self.play(
FadeOut(vectors),
Restore(frame),
run_time=2
)
self.wait(3)
class FourierOfPiSymbol5(FourierOfPiSymbol):
CONFIG = {
"n_vectors": 5,
"run_time": 10,
}
class FourierOfTrebleClef(FourierOfPiSymbol):
CONFIG = {
"n_vectors": 101,
"run_time": 10,
"start_drawn": True,
"file_name": "TrebleClef",
"height": 7.5,
}
def get_shape(self):
shape = SVGMobject(self.file_name)
return shape
def get_path(self):
shape = self.get_shape()
path = shape.family_members_with_points()[0]
path.set_height(self.height)
path.set_fill(opacity=0)
path.set_stroke(WHITE, 0)
return path
class FourierOfIP(FourierOfTrebleClef):
CONFIG = {
"file_name": "IP_logo2",
"height": 6,
"n_vectors": 100,
}
# def construct(self):
# path = self.get_path()
# self.add(path)
def get_shape(self):
shape = SVGMobject(self.file_name)
return shape
def get_path(self):
shape = self.get_shape()
path = shape.family_members_with_points()[0]
path.add_line_to(path.get_start())
# path.make_smooth()
path.set_height(self.height)
path.set_fill(opacity=0)
path.set_stroke(WHITE, 0)
return path
class FourierOfEighthNote(FourierOfTrebleClef):
CONFIG = {
"file_name": "EighthNote"
}
class FourierOfN(FourierOfTrebleClef):
CONFIG = {
"height": 6,
"n_vectors": 1000,
}
def get_shape(self):
return TexMobject("N")
class FourierNailAndGear(FourierOfTrebleClef):
CONFIG = {
"height": 6,
"n_vectors": 200,
"run_time": 100,
"slow_factor": 0.01,
"parametric_function_step_size": 0.0001,
"arrow_config": {
"tip_length": 0.1,
"stroke_width": 2,
}
}
def get_shape(self):
shape = SVGMobject("Nail_And_Gear")[1]
return shape
class FourierBatman(FourierOfTrebleClef):
CONFIG = {
"height": 4,
"n_vectors": 100,
"run_time": 10,
"arrow_config": {
"tip_length": 0.1,
"stroke_width": 2,
}
}
def get_shape(self):
shape = SVGMobject("BatmanLogo")[1]
return shape
class FourierHeart(FourierOfTrebleClef):
CONFIG = {
"height": 4,
"n_vectors": 100,
"run_time": 10,
"arrow_config": {
"tip_length": 0.1,
"stroke_width": 2,
}
}
def get_shape(self):
shape = SuitSymbol("hearts")
return shape
def get_drawn_path(self, *args, **kwargs):
kwargs["stroke_width"] = 5
path = super().get_drawn_path(*args, **kwargs)
path.set_color(PINK)
return path
class FourierNDQ(FourierOfTrebleClef):
CONFIG = {
"height": 4,
"n_vectors": 1000,
"run_time": 10,
"arrow_config": {
"tip_length": 0.1,
"stroke_width": 2,
}
}
def get_shape(self):
path = VMobject()
shape = TexMobject("NDQ")
for sp in shape.family_members_with_points():
path.append_points(sp.points)
return path
class FourierGoogleG(FourierOfTrebleClef):
CONFIG = {
"n_vectors": 10,
"height": 5,
"g_colors": [
"#4285F4",
"#DB4437",
"#F4B400",
"#0F9D58",
]
}
def get_shape(self):
g = SVGMobject("google_logo")[5]
g.center()
self.add(g)
return g
def get_drawn_path(self, *args, **kwargs):
kwargs["stroke_width"] = 7
path = super().get_drawn_path(*args, **kwargs)
blue, red, yellow, green = self.g_colors
path[:250].set_color(blue)
path[250:333].set_color(green)
path[333:370].set_color(yellow)
path[370:755].set_color(red)
path[755:780].set_color(yellow)
path[780:860].set_color(green)
path[860:].set_color(blue)
return path
class ExplainCircleAnimations(FourierCirclesScene):
CONFIG = {
"n_vectors": 100,
"center_point": 2 * DOWN,
"n_top_circles": 9,
"path_height": 3,
}
def construct(self):
self.add_path()
self.add_circles()
self.wait(8)
self.organize_circles_in_a_row()
self.show_frequencies()
self.show_examples_for_frequencies()
self.show_as_vectors()
self.show_vector_sum()
self.tweak_starting_vectors()
def add_path(self):
self.path = self.get_path()
self.add(self.path)
def add_circles(self):
coefs = self.get_coefficients_of_path(self.path)
self.circles = self.get_circles(coefficients=coefs)
self.add(self.circles)
self.drawn_path = self.get_drawn_path(self.circles)
self.add(self.drawn_path)
def organize_circles_in_a_row(self):
circles = self.circles
top_circles = circles[:self.n_top_circles].copy()
center_trackers = VGroup()
for circle in top_circles:
tracker = VectorizedPoint(circle.center_func())
circle.center_func = tracker.get_location
center_trackers.add(tracker)
tracker.freq = circle.freq
tracker.circle = circle
center_trackers.submobjects.sort(
key=lambda m: m.freq
)
center_trackers.generate_target()
right_buff = 1.45
center_trackers.target.arrange(RIGHT, buff=right_buff)
center_trackers.target.to_edge(UP, buff=1.25)
self.add(top_circles)
self.play(
MoveToTarget(center_trackers),
run_time=2
)
self.wait(4)
self.top_circles = top_circles
self.center_trackers = center_trackers
def show_frequencies(self):
center_trackers = self.center_trackers
freq_numbers = VGroup()
for ct in center_trackers:
number = Integer(ct.freq)
number.next_to(ct, DOWN, buff=1)
freq_numbers.add(number)
ct.circle.number = number
ld, rd = [
TexMobject("\\dots")
for x in range(2)
]
ld.next_to(freq_numbers, LEFT, MED_LARGE_BUFF)
rd.next_to(freq_numbers, RIGHT, MED_LARGE_BUFF)
freq_numbers.add_to_back(ld)
freq_numbers.add(rd)
freq_word = TextMobject("Frequencies")
freq_word.scale(1.5)
freq_word.set_color(YELLOW)
freq_word.next_to(freq_numbers, DOWN, MED_LARGE_BUFF)
self.play(
LaggedStartMap(
FadeInFromDown, freq_numbers
)
)
self.play(
Write(freq_word),
LaggedStartMap(
ShowCreationThenFadeAround, freq_numbers,
)
)
self.wait(2)
self.freq_numbers = freq_numbers
self.freq_word = freq_word
def show_examples_for_frequencies(self):
top_circles = self.top_circles
c1, c2, c3 = [
list(filter(
lambda c: c.freq == k,
top_circles
))[0]
for k in (1, 2, 3)
]
neg_circles = VGroup(*filter(
lambda c: c.freq < 0,
top_circles
))
for c in [c1, c2, c3, *neg_circles]:
c.rect = SurroundingRectangle(c)
self.play(
ShowCreation(c2.rect),
WiggleOutThenIn(c2.number),
)
self.wait(2)
self.play(
ReplacementTransform(c2.rect, c1.rect),
)
self.play(FadeOut(c1.rect))
self.wait()
self.play(
ShowCreation(c3.rect),
WiggleOutThenIn(c3.number),
)
self.play(
FadeOut(c3.rect),
)
self.wait(2)
self.play(
LaggedStart(*[
ShowCreationThenFadeOut(c.rect)
for c in neg_circles
])
)
self.wait(3)
self.play(FadeOut(self.freq_word))
def show_as_vectors(self):
top_circles = self.top_circles
top_vectors = self.get_rotating_vectors(top_circles)
top_vectors.set_color(WHITE)
original_circles = top_circles.copy()
self.play(
FadeIn(top_vectors),
top_circles.set_opacity, 0,
)
self.wait(3)
self.play(
top_circles.match_style, original_circles
)
self.remove(top_vectors)
self.top_vectors = top_vectors
def show_vector_sum(self):
trackers = self.center_trackers.copy()
trackers.sort(
submob_func=lambda t: abs(t.circle.freq - 0.1)
)
plane = self.plane = NumberPlane(
x_min=-3,
x_max=3,
y_min=-2,
y_max=2,
axis_config={
"stroke_color": LIGHT_GREY,
}
)
plane.set_stroke(width=1)
plane.fade(0.5)
plane.move_to(self.center_point)
self.play(
FadeOut(self.drawn_path),
FadeOut(self.circles),
self.slow_factor_tracker.set_value, 0.05,
)
self.add(plane, self.path)
self.play(FadeIn(plane))
new_circles = VGroup()
last_tracker = None
for tracker in trackers:
if last_tracker:
tracker.new_location_func = last_tracker.circle.get_start
else:
tracker.new_location_func = lambda: self.center_point
original_circle = tracker.circle
tracker.circle = original_circle.copy()
tracker.circle.center_func = tracker.get_location
new_circles.add(tracker.circle)
self.add(tracker, tracker.circle)
start_point = tracker.get_location()
self.play(
UpdateFromAlphaFunc(
tracker, lambda t, a: t.move_to(
interpolate(
start_point,
tracker.new_location_func(),
a,
)
),
run_time=2
)
)
tracker.add_updater(lambda t: t.move_to(
t.new_location_func()
))
self.wait(2)
last_tracker = tracker
self.wait(3)
self.clear()
self.slow_factor_tracker.set_value(0.1)
self.add(
self.top_circles,
self.freq_numbers,
self.path,
)
self.add_circles()
for tc in self.top_circles:
for c in self.circles:
if c.freq == tc.freq:
tc.rotate(
angle_of_vector(c.get_start() - c.get_center()) -
angle_of_vector(tc.get_start() - tc.get_center())
)
self.wait(10)
def tweak_starting_vectors(self):
top_circles = self.top_circles
circles = self.circles
path = self.path
drawn_path = self.drawn_path
new_path = self.get_new_path()
new_coefs = self.get_coefficients_of_path(new_path)
new_circles = self.get_circles(coefficients=new_coefs)
new_top_circles = VGroup()
new_top_vectors = VGroup()
for top_circle in top_circles:
for circle in new_circles:
if circle.freq == top_circle.freq:
new_top_circle = circle.copy()
new_top_circle.center_func = top_circle.get_center
new_top_vector = self.get_rotating_vector(
new_top_circle
)
new_top_circles.add(new_top_circle)
new_top_vectors.add(new_top_vector)
self.play(
self.slow_factor_tracker.set_value, 0,
FadeOut(drawn_path)
)
self.wait()
self.play(
ReplacementTransform(top_circles, new_top_circles),
ReplacementTransform(circles, new_circles),
FadeOut(path),
run_time=3,
)
new_drawn_path = self.get_drawn_path(
new_circles, stroke_width=4,
)
self.add(new_drawn_path)
self.slow_factor_tracker.set_value(0.1)
self.wait(20)
#
def configure_path(self, path):
path.set_stroke(WHITE, 1)
path.set_fill(BLACK, opacity=1)
path.set_height(self.path_height)
path.move_to(self.center_point)
return path
def get_path(self):
tex = TexMobject("f")
path = tex.family_members_with_points()[0]
self.configure_path(path)
return path
# return Square().set_height(3)
def get_new_path(self):
shape = SVGMobject("TrebleClef")
path = shape.family_members_with_points()[0]
self.configure_path(path)
path.scale(1.5, about_edge=DOWN)
return path