Value Tracker

The defined value tracker VMobject in value_tracker.py

• Class ValueTracker(Mobject)
• Class ExponentialValueTracker(ValueTracker)
• Class ComplexValueTracker(ValueTracker)

Class ValueTracker(Mobject)

ValueTracker is used to generate a value tracker Mobject for given parameters.

Example

Code

# folder/file: tut/manim_mobject_valuetracker_001a.py

import numpy as np
from manimlib.scene.scene import Scene
from manimlib.mobject.value_tracker import ValueTracker
from manimlib.mobject.geometry import Dot, Line
from manimlib.mobject.number_line import NumberLine
from manimlib.mobject.svg.tex_mobject import TexMobject
from manimlib.mobject.numbers import DecimalNumber, Integer

class manim_mobject_valuetracker_001a(Scene):
    def construct(self):
        def linear(t): return t
        def v_tracker(obj):
            obj.set_value(v.get_value())
            obj.set_x(v.get_value()-7)
        v=ValueTracker(1)
        self.add(NumberLine(x_min=-6,x_max=6).move_to([0,-1.5,0]))
        dotv = Dot().add_updater(lambda i: i.set_x(v.get_value()-7))
        self.add(dotv.move_to([-4,-1.5,0]))
        textv = DecimalNumber(v.get_value()).add_updater(v_tracker)
        self.add(textv.move_to([-4,-2.5,0]))
        self.play(v.set_value,13,rate_func=linear,run_time=2)
        self.wait()
        value1=ValueTracker(0.0000001)
        text1 = DecimalNumber(value1.get_value(),num_decimal_places=5).add_updater(lambda x: x.set_value(value1.get_value())).move_to([-3,3,0])
        self.add(text1)
        self.play(value1.set_value,1,run_time=2)
        self.wait()
        text2 = DecimalNumber(value1.get_value(),num_decimal_places=5)
        self.add(text2.move_to([3,3,0]))
        def update_text(obj):
            obj.set_value(np.cos(value1.get_value()))
        text2.add_updater(update_text)
        self.play(value1.set_value,0.0000001,run_time=2)
        self.wait()
        def update_tracker(obj,obj1):
            dx=x.get_value()-update_tracker.x
            obj.increment_value(-dx),
            if (x.get_value()**2+y.get_value()**2+z.get_value()**2) > 1 :
                obj.increment_value(dx)             
            update_tracker.x=x.get_value()
            z.set_value((1-x.get_value()**2-y.get_value()**2)**0.5)
            return obj.get_value()
        x=ValueTracker(1)
        update_tracker.x=x.get_value()
        y=ValueTracker(0)
        z=ValueTracker(0)
        self.add(Line((0,0,0)).move_to([-3.5,1.5,0]))
        dot1 = Dot().add_updater(lambda i: i.set_x(x.get_value()-4))
        self.add(dot1.move_to([-4,1.5,0]))
        self.add(Line((0,0,0)).move_to([-3.5,1,0]))
        dot2 = Dot().add_updater(lambda i: i.set_x(y.get_value()-4))
        self.add(dot2.move_to([-4-1,1,0]))
        self.add(Line((0,0,0)).move_to([-3.5,0.5,0]))
        dot3 = Dot().add_updater(lambda i: i.set_x(z.get_value()-4))
        self.add(dot3.move_to([-4-1,0.5,0]))
        def update_texty(obj):
            obj.set_value(update_tracker(y,x))
        textx = DecimalNumber(x.get_value(),num_decimal_places=5).add_updater(lambda i: i.set_value(x.get_value()))
        self.add(textx.move_to([-4+2,1.5,0]))
        texty = DecimalNumber(y.get_value(),num_decimal_places=5).add_updater(update_texty)
        self.add(texty.move_to([-4+2,1,0]))
        textz = DecimalNumber(z.get_value(),num_decimal_places=5).add_updater(lambda i: i.set_value(z.get_value()))
        self.add(textz.move_to([-4+2,0.5,0]))
        total = DecimalNumber(1,num_decimal_places=22).add_updater(lambda i: i.set_value((x.get_value()**2+y.get_value()**2+z.get_value()**2)))
        self.add(total.next_to(texty,buff=0.7))
        self.play(x.set_value,0.0000001,run_time=2)
        self.wait()

Output

Class ExponentialValueTracker(ValueTracker)

ExponentialValueTracker is used to generate a exponential value tracker Mobject for given parameters.

Example

Code

# folder/file: tut/manim_mobject_ExponentialValueTracker_001a.py

import numpy as np
from manimlib.scene.scene import Scene
from manimlib.mobject.value_tracker import ExponentialValueTracker
from manimlib.mobject.geometry import Dot, Line
from manimlib.mobject.number_line import NumberLine
from manimlib.mobject.svg.tex_mobject import TexMobject
from manimlib.mobject.numbers import DecimalNumber, Integer

class manim_mobject_ExponentialValueTracker_001a(Scene):
    def construct(self):
        def linear(t): return t
        def e_tracker(obj):
            obj.set_value(e.get_value())
            obj.set_x(e.get_value()-7)
            textv.set_x(np.log(e.get_value())*12/np.log(13)-6)
        e=ExponentialValueTracker(1)
        self.add(NumberLine(x_min=-6,x_max=6).move_to([0,-1.5,0]))
        dotv = Dot(radius=0.15,color="#FF3300").add_updater(lambda i: i.set_x(np.log(e.get_value())*12/np.log(13)-6))
        self.add(dotv.move_to([-4,-1.5,0]))
        textv = DecimalNumber(e.get_value()).add_updater(lambda i: i.set_value(np.log(e.get_value())*12/np.log(13)+1))
        self.add(textv.move_to([-4,-0.5,0]))
        dote = Dot().add_updater(lambda i: i.set_x(e.get_value()-7))
        self.add(dote.move_to([-4,-1.5,0]))
        texte = DecimalNumber(e.get_value()).add_updater(e_tracker)
        self.add(texte.move_to([-4,-2.5,0]))
        self.play(e.set_value,13,rate_func=linear,run_time=2)
        self.wait()
        value1=ExponentialValueTracker(0.0000001)
        text1 = DecimalNumber(value1.get_value(),num_decimal_places=5).add_updater(lambda x: x.set_value(value1.get_value())).move_to([-3,3,0])
        self.add(text1)
        self.play(value1.set_value,1,run_time=2)
        self.wait()
        text2 = DecimalNumber(value1.get_value(),num_decimal_places=5)
        self.add(text2.move_to([3,3,0]))
        def update_text(obj):
            obj.set_value(np.cos(value1.get_value()))
        text2.add_updater(update_text)
        self.play(value1.set_value,0.0000001,run_time=2)
        self.wait()
        def update_tracker(obj,obj1):
            dx=x.get_value()-update_tracker.x
            obj.increment_value(-dx),
            if (x.get_value()**2+y.get_value()**2+z.get_value()**2) > 1 :
                obj.increment_value(dx)             
            update_tracker.x=x.get_value()
            z.set_value((1-x.get_value()**2-y.get_value()**2)**0.5)
            return obj.get_value()
        x=ExponentialValueTracker(1)
        update_tracker.x=x.get_value()
        y=ExponentialValueTracker(0)
        z=ExponentialValueTracker(0)
        self.add(Line((0,0,0)).move_to([-3.5,1.5,0]))
        dot1 = Dot().add_updater(lambda i: i.set_x(x.get_value()-4))
        self.add(dot1.move_to([-4,1.5,0]))
        self.add(Line((0,0,0)).move_to([-3.5,1,0]))
        dot2 = Dot().add_updater(lambda i: i.set_x(y.get_value()-4))
        self.add(dot2.move_to([-4-1,1,0]))
        self.add(Line((0,0,0)).move_to([-3.5,0.5,0]))
        dot3 = Dot().add_updater(lambda i: i.set_x(z.get_value()-4))
        self.add(dot3.move_to([-4-1,0.5,0]))
        def update_texty(obj):
            obj.set_value(update_tracker(y,x))
        textx = DecimalNumber(x.get_value(),num_decimal_places=5).add_updater(lambda i: i.set_value(x.get_value()))
        self.add(textx.move_to([-4+2,1.5,0]))
        texty = DecimalNumber(y.get_value(),num_decimal_places=5).add_updater(update_texty)
        self.add(texty.move_to([-4+2,1,0]))
        textz = DecimalNumber(z.get_value(),num_decimal_places=5).add_updater(lambda i: i.set_value(z.get_value()))
        self.add(textz.move_to([-4+2,0.5,0]))
        total = DecimalNumber(1,num_decimal_places=22).add_updater(lambda i: i.set_value((x.get_value()**2+y.get_value()**2+z.get_value()**2)))
        self.add(total.next_to(texty,buff=0.7))
        self.play(x.set_value,0.0000001,run_time=2)
        self.wait()

Output

Class ComplexValueTracker(ValueTracker)

ComplexValueTracker is used to generate a complex value tracker Mobject for given parameters.

Example

Code

# folder/file: tut/manim_mobject_ComplexValueTracker_001a.py

import numpy as np
from manimlib.scene.scene import Scene
from manimlib.mobject.value_tracker import ComplexValueTracker, ValueTracker
from manimlib.mobject.geometry import Dot, Line, Circle
from manimlib.mobject.number_line import NumberLine
from manimlib.mobject.svg.tex_mobject import TexMobject
from manimlib.mobject.numbers import DecimalNumber, Integer

class manim_mobject_ComplexValueTracker_001a(Scene):
    def construct(self):
        def linear(t): return t
        def v_tracker(obj):
            obj.set_value(v.get_value())
            p_tracker(obj)
        def p_tracker(obj):
            obj.set_x(v.get_value().real)
            obj.set_y(v.get_value().imag)
        v=ComplexValueTracker(complex(5.5,3.5))
        self.add(NumberLine(x_min=-6,x_max=6))
        self.add(NumberLine(x_min=-4,x_max=4).rotate(1.5708))
        dotv = Dot(color="#FF3300").add_updater(p_tracker)
        self.add(dotv.move_to([5.5,3.5,0]))
        textv = DecimalNumber(v.get_value()).add_updater(v_tracker)
        self.add(textv.move_to([5.5,3.5,0]))
        self.play(v.set_value,complex(-5.5,-3.5),rate_func=linear,run_time=2)
        self.wait()
        def s_tracker(obj):
            obj.set_value(np.abs(s.get_value())**0.5)
            obj.set_y(np.abs(s.get_value())**0.5)
        s=ComplexValueTracker(complex(5.5,3.5))
        dots = Dot(color="#FF3300").add_updater(lambda x: x.set_y(np.abs(s.get_value())**0.5))
        self.add(dots.move_to([0,0,0]))
        texts = DecimalNumber(s.get_value()).add_updater(s_tracker)
        self.add(texts.next_to(dots,buff=1))
        self.play(s.set_value,complex(-3.5,-3.5),rate_func=linear,run_time=2)
        self.wait()
        s.set_value(complex(5.5,3.5))
        circle1=Circle()
        self.add(circle1)        
        circle1.i=circle1.copy()
        def a_tracker(obj):
            obj.become(Circle())
            obj.scale(np.abs(s.get_value())**0.5)
        circle1.add_updater(a_tracker)
        self.add(circle1)
        self.play(s.set_value,complex(-3.5,-3.5),rate_func=linear,run_time=2)
        self.wait()
        i=ComplexValueTracker(complex(5.5,3.5))
        circle1=Circle()
        self.add(circle1)        
        circle1.i=circle1.copy()
        def i_tracker(obj):
            obj.become(Circle())
            obj.scale(i.get_value().real)
        circle1.add_updater(i_tracker)
        self.add(circle1)
        self.play(i.set_value,complex(-3.5,-3.5),rate_func=linear,run_time=2)
        self.wait()

Output