Finished giant PiecewiseConstantPlot scene

This commit is contained in:
Grant Sanderson 2017-04-12 17:16:20 -07:00
parent d30c77c78d
commit 326e7fc76f

View file

@ -570,7 +570,6 @@ class ConstantVelocityPlot(PlotVelocity):
self.comment_on_area_wierdness()
self.note_units()
def draw_graph(self):
graph = self.get_graph(
lambda t : 10,
@ -674,6 +673,27 @@ class ConstantVelocityPlot(PlotVelocity):
for axis in self.x_axis, self.y_axis
])
lines.highlight(TIME_COLOR)
square = Square(
stroke_color = BLACK,
stroke_width = 1,
fill_color = PINK,
fill_opacity = 1,
)
square.replace(
VGroup(*[
VectorizedPoint(self.coords_to_point(i, i))
for i in 0, 1
]),
stretch = True
)
units_of_area = VGroup(*[
square.copy().move_to(
self.coords_to_point(x, y),
DOWN+LEFT
)
for x in range(8)
for y in range(10)
])
self.play(ShowCreation(x_line))
self.play(Indicate(self.x_axis_label_mob))
@ -684,29 +704,625 @@ class ConstantVelocityPlot(PlotVelocity):
)
self.play(Indicate(self.y_axis_label_mob))
self.play(FadeOut(y_line))
self.dither()
for direction in UP, DOWN:
for FadeClass in FadeIn, FadeOut:
self.play(
ApplyWave(
self.area_rect,
run_time = 1,
direction = direction,
amplitude = MED_SMALL_BUFF,
FadeClass(
units_of_area,
submobject_mode = "lagged_start",
run_time = 3
),
*map(Animation, self.get_mobjects()) + [
Animation(self.s_label),
self.randy.look_at, self.area_rect
)
self.play(Blink(self.randy))
self.dither()
class PiecewiseConstantCar(Scene):
def construct(self):
car = Car()
start_point = 5*LEFT
car.move_to(start_point)
self.add(car)
self.dither()
for shift in 2, 6, 12:
car.randy.rotate_in_place(np.pi/8)
anim = MoveCar(
car, start_point+shift*RIGHT,
rate_func = None
)
anim.target_mobject[0].rotate_in_place(-np.pi/8)
# for mob in anim.starting_mobject, anim.mobject:
# mob.randy.rotate_in_place(np.pi/6)
self.play(anim)
self.dither()
class PiecewiseConstantPlot(PlotVelocity):
CONFIG = {
"y_axis_label" : "",
"min_graph_proportion" : 0.1,
"max_graph_proportion" : 0.8,
"num_riemann_approximations" : 7, ##TODO
"riemann_rect_fill_opacity" : 0.75,
"tick_size" : 0.2,
}
def construct(self):
self.setup_graph()
self.always_changing()
self.show_piecewise_constant_graph()
self.compute_distance_on_each_interval()
self.approximate_original_curve()
self.revert_to_specific_approximation()
self.show_specific_rectangle()
self.show_v_dt_for_all_rectangles()
self.write_integral_symbol()
self.roles_of_dt()
self.what_does_sum_approach()
def setup_graph(self):
self.setup_axes()
self.add(*self.get_v_graph_and_label())
def always_changing(self):
dot = Dot()
arrow = Arrow(LEFT, RIGHT)
words = TextMobject("Always changing")
group = VGroup(dot, arrow, words)
def update_group(group, alpha):
dot, arrow, words = group
prop = interpolate(
self.min_graph_proportion,
self.max_graph_proportion,
alpha
)
graph_point = self.v_graph.point_from_proportion(prop)
dot.move_to(graph_point)
x_val = self.x_axis.point_to_number(graph_point)
angle = self.angle_of_tangent(x_val, self.v_graph)
angle += np.pi/2
vect = rotate_vector(RIGHT, angle)
arrow.rotate(angle - arrow.get_angle() + np.pi)
arrow.shift(
graph_point + MED_SMALL_BUFF*vect - arrow.get_end()
)
words.next_to(arrow.get_start(), UP)
return group
update_group(group, 0)
self.play(
Write(words),
ShowCreation(arrow),
DrawBorderThenFill(dot),
run_time = 1
)
self.play(UpdateFromAlphaFunc(
group, update_group,
rate_func = there_and_back,
run_time = 5
))
self.dither()
self.play(FadeOut(group))
def show_piecewise_constant_graph(self):
pw_constant_graph = self.get_pw_constant_graph()
alt_lines = [
line.copy().highlight(YELLOW)
for line in pw_constant_graph[:4]
]
for line in alt_lines:
line.start_dot = Dot(line.get_start())
line.end_dot = Dot(line.get_end())
VGroup(line.start_dot, line.end_dot).highlight(line.get_color())
line = alt_lines[0]
faders = [self.v_graph, self.v_graph_label]
for mob in faders:
mob.save_state()
mob.generate_target()
mob.target.fade(0.7)
self.play(*map(MoveToTarget, faders))
self.play(ShowCreation(pw_constant_graph, run_time = 2))
self.dither()
self.play(ShowCreation(line))
self.dither()
for new_line in alt_lines[1:]:
for mob in line.end_dot, new_line.start_dot, new_line:
self.play(Transform(
line, mob,
run_time = 1./3
))
self.remove(line)
self.add(new_line)
self.dither(2)
line = new_line
self.play(FadeOut(line))
self.pw_constant_graph = pw_constant_graph
def compute_distance_on_each_interval(self):
rect_list = self.get_riemann_rectangles_list(
self.v_graph, self.num_riemann_approximations,
max_dx = 1,
x_min = 0,
x_max = 8,
)
for rects in rect_list:
rects.set_fill(opacity = self.riemann_rect_fill_opacity)
flat_rects = self.get_riemann_rectangles(
self.get_graph(lambda t : 0),
x_min = 0, x_max = 8, dx = 1
)
rects = rect_list[0]
rect = rects[1]
flat_rects.submobjects[1] = rect.copy()
right_brace = Brace(rect, RIGHT)
top_brace = Brace(rect, UP)
right_brace.label = right_brace.get_text("$7\\frac{\\text{m}}{\\text{s}}$")
top_brace.label = top_brace.get_text("$1$s")
self.play(FadeIn(rect))
for brace in right_brace, top_brace:
self.play(
GrowFromCenter(brace),
Write(brace.label, run_time = 1),
)
brace.add(brace.label)
self.dither()
self.play(
ReplacementTransform(
flat_rects, rects,
run_time = 2,
submobject_mode = "lagged_start",
),
Animation(right_brace)
)
self.play(*map(FadeOut, [top_brace, right_brace]))
self.dither()
self.rects = rects
self.rect_list = rect_list
def approximate_original_curve(self):
rects = self.rects
self.play(
FadeOut(self.pw_constant_graph),
*[
m.restore
for m in self.v_graph, self.v_graph_label
]+[Animation(self.rects)]
)
for new_rects in self.rect_list[1:]:
rects.align_submobjects(new_rects)
for every_other_rect in rects[::2]:
every_other_rect.set_fill(opacity = 0)
self.play(Transform(
rects, new_rects,
run_time = 2,
submobject_mode = "lagged_start"
))
self.dither()
def revert_to_specific_approximation(self):
rects = self.rects
rects.save_state()
target_rects = self.rect_list[2]
target_rects.set_fill(opacity = 1)
ticks = self.get_ticks(target_rects)
tick_pair = VGroup(*ticks[4:6])
brace = Brace(tick_pair, DOWN, buff = 0)
dt_label = brace.get_text("$dt$", buff = SMALL_BUFF)
example_text = TextMobject(
"For example, \\\\",
"$dt$", "$=0.25$"
)
example_text.to_corner(UP+RIGHT)
example_text.highlight_by_tex("dt", YELLOW)
self.play(ReplacementTransform(
rects, target_rects,
run_time = 2,
submobject_mode = "lagged_start"
))
rects.restore()
self.dither()
self.play(
ShowCreation(ticks),
FadeOut(self.x_axis.numbers)
)
self.play(
GrowFromCenter(brace),
Write(dt_label)
)
self.dither()
self.play(
FadeIn(
example_text,
run_time = 2,
submobject_mode = "lagged_start",
),
ReplacementTransform(
dt_label.copy(),
example_text.get_part_by_tex("dt")
)
)
self.dither()
self.rects = rects = target_rects
self.ticks = ticks
self.dt_brace = brace
self.dt_label = dt_label
self.dt_example_text = example_text
def show_specific_rectangle(self):
rects = self.rects
rect = rects[4].copy()
rect_top = Line(
rect.get_corner(UP+LEFT),
rect.get_corner(UP+RIGHT),
color = self.v_graph.get_color()
)
t_vals = [1, 1.25]
t_labels = VGroup(*[
TexMobject("t=%s"%str(t))
for t in t_vals
])
t_labels.scale(0.7)
t_labels.next_to(rect, DOWN)
for vect, label in zip([LEFT, RIGHT], t_labels):
label.shift(1.5*vect)
label.add(Arrow(
label.get_edge_center(-vect),
rect.get_corner(DOWN+vect),
buff = SMALL_BUFF,
tip_length = 0.15,
color = WHITE
))
v_lines = VGroup()
h_lines = VGroup()
height_labels = VGroup()
for t in t_vals:
v_line = self.get_vertical_line_to_graph(
t, self.v_graph,
color = YELLOW
)
y_axis_point = self.graph_origin[0]*RIGHT
y_axis_point += v_line.get_end()[1]*UP
h_line = DashedLine(v_line.get_end(), y_axis_point)
label = TexMobject("%.1f"%v_func(t))
label.scale(0.5)
label.next_to(h_line, LEFT, SMALL_BUFF)
v_lines.add(v_line)
h_lines.add(h_line)
height_labels.add(label)
circle = Circle(radius = 0.25, color = WHITE)
circle.move_to(rect.get_top())
self.play(
rects.set_fill, None, 0.25,
Animation(rect)
)
self.dither()
for label in t_labels:
self.play(FadeIn(label))
self.dither()
for v_line, h_line, label in zip(v_lines, h_lines, height_labels):
self.play(ShowCreation(v_line))
self.play(ShowCreation(h_line))
self.play(Write(label, run_time = 1))
self.dither()
self.dither()
t_label_copy = t_labels[0].copy()
self.play(
t_label_copy.scale, 1./0.7,
t_label_copy.next_to, self.v_graph_label, DOWN+LEFT, 0
)
self.dither()
self.play(FadeOut(t_label_copy))
self.dither()
self.play(ShowCreation(circle))
self.play(ShowCreation(rect_top))
self.play(FadeOut(circle))
rect.add(rect_top)
self.dither()
for x in range(2):
self.play(
rect.scale_to_fit_height, v_lines[1].get_height(),
rect.move_to, rect.get_bottom(), DOWN,
run_time = 4,
rate_func = there_and_back
)
self.play(*map(FadeOut, [
group[1]
for group in v_lines, h_lines, height_labels
]))
self.play(
v_lines[0].highlight, RED,
rate_func = there_and_back,
)
self.dither()
area = TextMobject(
"7$\\frac{\\text{m}}{\\text{s}}$",
"$\\times$",
"0.25s",
"=",
"1.75m"
)
area.next_to(rect, RIGHT, LARGE_BUFF)
arrow = Arrow(
area.get_left(), rect.get_center(),
buff = 0,
color = WHITE
)
area.shift(SMALL_BUFF*RIGHT)
self.play(
Write(area),
ShowCreation(arrow)
)
self.dither(2)
self.play(*map(FadeOut, [
area, arrow,
v_lines[0], h_lines[0], height_labels[0],
rect, t_labels
]))
def show_v_dt_for_all_rectangles(self):
dt_brace_group = VGroup(self.dt_brace, self.dt_label)
rects_subset = self.rects[10:15]
last_rect = None
for rect in rects_subset:
brace = Brace(rect, LEFT, buff = 0)
v_t = TexMobject("v(t)")
v_t.next_to(brace, LEFT, SMALL_BUFF)
anims = [
rect.set_fill, None, 1,
dt_brace_group.next_to, rect, DOWN, SMALL_BUFF
]
if last_rect is not None:
anims += [
last_rect.set_fill, None, 0.25,
ReplacementTransform(last_brace, brace),
ReplacementTransform(last_v_t, v_t),
]
else:
anims += [
GrowFromCenter(brace),
Write(v_t)
]
self.play(*anims)
self.dither()
last_rect = rect
last_brace = brace
last_v_t = v_t
self.v_t = last_v_t
self.v_t_brace = last_brace
def write_integral_symbol(self):
integral = TexMobject(
"\\int", "^8", "_0", "v(t)", "\\,dt"
)
integral.to_corner(UP+RIGHT)
int_copy = integral.get_part_by_tex("int").copy()
bounds = map(integral.get_part_by_tex, ["0", "8"])
sum_word = TextMobject("``Sum''")
sum_word.next_to(integral, DOWN, MED_LARGE_BUFF, LEFT)
alt_sum_word = sum_word.copy()
int_symbol = TexMobject("\\int")
int_symbol.replace(alt_sum_word[1], dim_to_match = 1)
alt_sum_word.submobjects[1] = int_symbol
self.play(FadeOut(self.dt_example_text))
self.play(Write(integral.get_part_by_tex("int")))
self.dither()
self.play(Transform(int_copy, int_symbol))
self.play(Write(alt_sum_word), Animation(int_copy))
self.remove(int_copy)
self.play(ReplacementTransform(alt_sum_word, sum_word))
self.dither()
for bound in bounds:
self.play(Write(bound))
self.dither()
for bound, num in zip(bounds, [0, 8]):
bound_copy = bound.copy()
point = self.coords_to_point(num, 0)
self.play(
bound_copy.scale, 1.5,
bound_copy.next_to, point, DOWN, MED_LARGE_BUFF
)
self.play(ApplyWave(self.ticks, direction = UP))
self.dither()
for mob, tex in (self.v_t, "v(t)"), (self.dt_label, "dt"):
self.play(ReplacementTransform(
mob.copy().highlight(YELLOW),
integral.get_part_by_tex(tex),
run_time = 2
))
self.dither()
self.integral = integral
self.sum_word = sum_word
def roles_of_dt(self):
rects = self.rects
next_rects = self.rect_list[3]
morty = Mortimer().flip()
morty.to_corner(DOWN+LEFT)
int_dt = self.integral.get_part_by_tex("dt")
dt_copy = int_dt.copy()
self.play(FadeIn(morty))
self.play(
morty.change_mode, "raise_right_hand",
morty.look, UP+RIGHT,
dt_copy.next_to, morty.get_corner(UP+RIGHT), UP,
dt_copy.highlight, YELLOW
)
self.play(Blink(morty))
self.play(
ReplacementTransform(
dt_copy.copy(), int_dt,
run_time = 2
),
morty.look_at, int_dt
)
self.dither(2)
self.play(
ReplacementTransform(dt_copy.copy(), self.dt_label),
morty.look_at, self.dt_label
)
self.play(*[
ApplyMethod(
tick.shift, tick.get_height()*UP/2,
run_time = 2,
rate_func = squish_rate_func(
there_and_back,
alpha, alpha+0.2,
)
)
for tick, alpha in zip(
self.ticks,
np.linspace(0, 0.8, len(self.ticks))
)
])
self.dither()
#Shrink dt just a bit
self.play(
morty.change_mode, "pondering",
rects.set_fill, None, 0.75,
*map(FadeOut, [
dt_copy, self.v_t, self.v_t_brace
])
)
rects.align_submobjects(next_rects)
for every_other_rect in rects[::2]:
every_other_rect.set_fill(opacity = 0)
self.play(
self.dt_brace.stretch, 0.5, 0,
self.dt_brace.move_to, self.dt_brace, LEFT,
ReplacementTransform(
rects, next_rects,
run_time = 2,
submobject_mode = "lagged_start"
),
Transform(
self.ticks, self.get_ticks(next_rects),
run_time = 2,
submobject_mode = "lagged_start",
),
)
self.rects = rects = next_rects
self.dither()
self.play(Blink(morty))
self.play(*[
ApplyFunction(
lambda r : r.shift(0.2*UP).set_fill(None, 1),
rect,
run_time = 2,
rate_func = squish_rate_func(
there_and_back,
alpha, alpha+0.2,
)
)
for rect, alpha in zip(
rects,
np.linspace(0, 0.8, len(rects))
)
]+[
morty.change_mode, "thinking",
])
self.dither()
self.morty = morty
def what_does_sum_approach(self):
morty = self.morty
rects = self.rects
cross = TexMobject("\\times")
cross.replace(self.sum_word, stretch = True)
cross.highlight(RED)
brace = Brace(self.integral, DOWN)
dt_to_0 = brace.get_text("$dt \\to 0$")
self.play(PiCreatureSays(
morty, "Why not $\\Sigma$?",
target_mode = "sassy"
))
self.play(Blink(morty))
self.dither()
self.play(Write(cross))
self.dither()
self.play(
RemovePiCreatureBubble(morty, target_mode = "plain"),
*map(FadeOut, [
cross, self.sum_word, self.ticks,
self.dt_brace, self.dt_label,
])
)
self.play(FadeIn(brace), FadeIn(dt_to_0))
for new_rects in self.rect_list[4:]:
rects.align_submobjects(new_rects)
for every_other_rect in rects[::2]:
every_other_rect.set_fill(opacity = 0)
self.play(
Transform(
rects, new_rects,
run_time = 2,
submobject_mode = "lagged_start"
),
morty.look_at, rects,
)
self.dither()
#####
def get_pw_constant_graph(self):
result = VGroup()
for left_x in range(8):
xs = [left_x, left_x+1]
y = self.v_graph.underlying_function(left_x)
line = Line(*[
self.coords_to_point(x, y)
for x in xs
])
line.highlight(self.v_graph.get_color())
result.add(line)
return result
def get_ticks(self, rects):
ticks = VGroup(*[
Line(
point+self.tick_size*UP/2,
point+self.tick_size*DOWN/2
)
for t in np.linspace(0, 8, len(rects)+1)
for point in [self.coords_to_point(t, 0)]
])
ticks.highlight(YELLOW)
return ticks
class CarJourneyApproximations(Scene):
def construct(self):
pass