Problems with cached data in a scene with .add_updater [SCENE CACHING]

[kolibril13]

class UpdaterExample(Scene):
    def construct(self):
        path = VMobject()
        dot = Dot()
        path.set_points_as_corners([dot.get_center(), dot.get_center()])

        def update_path(path):
            previus_path = path.copy()
            previus_path.add_points_as_corners([dot.get_center()])
            path.become(previus_path)

        path.add_updater(update_path)
        self.add(path, dot)
        self.play(Rotating(dot, radians=PI, about_point=RIGHT, run_time=2))
        self.play(dot.shift, UP)
        self.play(dot.shift, LEFT)

When I run this script the first time, I get this:

However, when I run it again, without any changes, I get this:

and the following output in the terminal:

INFO      Animation 0 : Using cached data (hash :                   scene.py:807
          64312035_2472655632_2531679001)                                       
INFO                                                    scene_file_writer.py:616
          File ready at /home/kolibril/Downloads/Upd                         
          aterExample.gif                                                       
                                                                                
INFO      Rendered UpdaterExample                                   scene.py:120
          Played 3 animations    

[huguesdevimeux]

This bug is really wierd and seems to be related to the partial movies files (i.e manim does use the right ones, in the right order).

One question tho : There is actually 4 scene.play invocation but on the log there is only Animations 0. What does happen the first render ? is there only Animation 0 (and not Animation 1, etc) And with --disable_caching ?

[kolibril13]

When I run it with --disable_caching everything is fine.
Log is then:

Animation 0: RotatingDot: 100%|██████████| 60/60 [00:02<00:00, 23.70it/s]
Animation 1: MoveToTargetDot: 100%|██████████| 30/30 [00:02<00:00, 10.25it/s]
Animation 2: MoveToTargetDot: 100%|██████████| 30/30 [00:04<00:00,  6.85it/s]
INFO                                                    scene_file_writer.py:616
          File ready at /home/jan-hendrik/projects/mani                         
          m-community/example_scenes/media/videos/testi                         
          ng/720p30/UpdaterExampleXX.mp4                                        
                                                                                
INFO      Rendered UpdaterExampleXX                                 scene.py:120
          Played 3 animations                                                   

Process finished with exit code 0

When I run it the first time with cashing
the log looks like this:

Animation 0: RotatingDot: 100%|██████████| 60/60 [00:02<00:00, 24.67it/s]
Animation 1: MoveToTargetDot: 100%|██████████| 30/30 [00:02<00:00, 10.53it/s]
Animation 2: MoveToTargetDot: 100%|██████████| 30/30 [00:04<00:00,  6.75it/s]
INFO                                                    scene_file_writer.py:616
          File ready at /home/jan-hendrik/projects/mani                         
          m-community/example_scenes/media/videos/testi                         
          ng/720p30/UpdaterExampleXXX.mp4                                       
                                                                                
INFO      Rendered UpdaterExampleXXX                                scene.py:120
          Played 3 animations                                                   

Process finished with exit code 0

When I run it a second time with cashing, it looks like this:

INFO      Animation 0 : Using cached data (hash :                   scene.py:807
          3360453466_2472655632_2531679001)                                     
Animation 0: RotatingDot: 100%|██████████| 1/1 [00:00<00:00, 115.10it/s]
Animation 1: MoveToTargetDot: 100%|██████████| 30/30 [00:00<00:00, 38.36it/s]
Animation 2: MoveToTargetDot: 100%|██████████| 30/30 [00:01<00:00, 17.36it/s]
INFO                                                    scene_file_writer.py:616
          File ready at /home/jan-hendrik/projects/mani                         
          m-community/example_scenes/media/videos/testi                         
          ng/720p30/UpdaterExampleXXX.mp4                                       
                                                                                
INFO      Rendered UpdaterExampleXXX                                scene.py:120
          Played 3 animations                                                   

Process finished with exit code 0

[leotrs]

I'm trying to make sense of the second output. How is it possible that the curved line is being replaced by a straight line at the same endpoints?

[Aathish04]

My hunch is that the scene cacher only saw the positions of the Dot before and after, not taking into consideration the path that it travelled.

[leotrs]

Right, but I thought the scene cacher just used a previously rendered scene. No previously rendered scene had a straight line.

[Aathish04]

When I did the same test, the caching mechanism didn't use a cached file. It rerendered the file corresponding to the self.play(dot.shift, UP), and self.play(dot.shift, LEFT).

It's not recognising that nothing actually changed, for some reason...

[huguesdevimeux]

Right, but I thought the scene cacher just used a previously rendered scene. No previously rendered scene had a straight line.

You're right, so this is a very strange issue. scene-cacher never creates new partial-movie-files but uses some old ones.

@kolibril13 Could you try to flush the cash ? Use --flush_cache flag.

[kolibril13]

When I run it once with --flush_cache flag, the next one is ok, but the 2nd one has the same problem.

And when I run it with the -s flag, it always gives this result:

[huguesdevimeux]

Could you show what you get with --disable_caching ?

[kolibril13]

[huguesdevimeux]

(COuld you show the gif with --disable_caching please) (edit your answer, so we will have a clear discussion)

[huguesdevimeux]

You didn't render it with --disable_caching, didn't you? (and just send the resulting render gif :D)

[kolibril13]

Sorry, I made it with --flush_cache.
When I render it with --disable_caching, it looks like it should look, all the time