Scene Updater and Mobject Updater different behaviour

[Pasquale19]

Hey I was working on an animation involving a ValueTracker. I noticed a little ankward behaviour because it seems like the updating doesn’t work as expected. I was using a Scene updater to change many mobjects like Dot, Arrow …. I was using the VsCode Manim Sideview and it looked like the Value Tracker doesn’t get animated and just jumps to the value defined by valueTracker.set_value(). Then I tried to create a minimal example and discovered if I add the updater to the mobject everything works as expected. When I added the updater to the Scene the animation didn’t work properly. Can you explain me why this is happening? Do you get the same behaviour?

Here is an example with a Mobject Updater:
`

class ValueTrackerScene(Scene):
    '''object update example'''
    def construct(self):
        value_tracker = ValueTracker(0)

        moving_point = Dot(color=BLUE).move_to(LEFT * 3)

        value_text = Text("Value: 0").next_to(moving_point, UP)

        arrow = Arrow(start=ORIGIN, end=moving_point.get_center(), color=RED)

        # Update function to change the position of the point, text, and arrow
        def update_objects(mob):
            new_x = value_tracker.get_value()
            moving_point.move_to(LEFT * 3 + RIGHT * new_x)
            
            new_text = Text(f"Value: {value_tracker.get_value()}")
            value_text.become(new_text)  # Replace the old text with new text

            arrow.put_start_and_end_on(ORIGIN, moving_point.get_center())

        # Add updater to update objects whenever the ValueTracker changes
        self.add(moving_point, value_text, arrow)
        moving_point.add_updater(update_objects)
        #value_text.add_updater(update_objects)
        #arrow.add_updater(update_objects)
        #self.add_updater(update_objects)
    
        self.play(value_tracker.animate.set_value(5), run_time=3)  # Move to 5
        self.wait(1)
        self.play(value_tracker.animate.set_value(-3), run_time=3)  # Move to -3
        self.wait(1)

`
The example with a Scene Updater:

`

class ValueTrackerScene2(Scene):
    def construct(self):
        value_tracker = ValueTracker(0)

        # Create a point that will move based on the ValueTracker
        moving_point = Dot(color=BLUE).move_to(LEFT * 3)

        # Create an initial text object to display the current value
        value_text = Text("Value: 0").next_to(moving_point, UP)

        # Create an arrow that will point from the origin to the moving point
        arrow = Arrow(start=ORIGIN, end=moving_point.get_center(), color=RED)

        # Update function to change the position of the point, text, and arrow
        def update_objects(mob):
            new_x = value_tracker.get_value()
            moving_point.move_to(LEFT * 3 + RIGHT * new_x)
            
            new_text = Text(f"Value: {value_tracker.get_value()}")
            value_text.become(new_text)  # Replace the old text with new text
            
            arrow.put_start_and_end_on(ORIGIN, moving_point.get_center())

        # Add updater to update objects whenever the ValueTracker changes
        self.add(moving_point, value_text, arrow)
        #moving_point.add_updater(update_objects)
        #value_text.add_updater(update_objects)
        #arrow.add_updater(update_objects)
        self.add_updater(update_objects)
        self.play(value_tracker.animate.set_value(5), run_time=3)  # Move to 5
        self.wait(1)
        
        self.play(value_tracker.animate.set_value(-3), run_time=3)  # Move to -3
        self.wait(1)

`