MovingCamera rotation squishes objects instead of rotating

[meawplex-plus]

Description of bug / unexpected behavior

When I apply the animation self.camera.frame.animate.rotate(PI/2) to the scene and compile the animation with manim scene.py -pqh myScene, all mobjects (I used a single Square mobject with default properties) are squished instead of rotated.

Expected behavior

I expected the camera to rotate by PI/2 radians (90 degrees) without squishing.

How to reproduce the issue

Code for reproducing the problem

Add to scene.py:

class CameraIssue(MovingCameraScene):
    def construct(self):
        self.add(Square())
        self.play(self.camera.frame.animate.rotate(PI/2))

Compile with manim scene.py -pqh CameraIssue.

Additional media files

Images/GIFs

CameraIssue.mp4

Logs

Terminal output

Manim Community v0.17.3

[09/20/23 15:53:42] DEBUG    Hashing ...                                             hashing.py:350
                    DEBUG    Hashing done in 0.003948 s.                             hashing.py:362
                    DEBUG    Hash generated :  1433715038_3210132319_2428177325      hashing.py:365
                    DEBUG    List of the first few animation hashes of the     cairo_renderer.py:87
                             scene: ['1433715038_3210132319_2428177325']
[09/20/23 15:53:43] INFO     Animation 0 : Partial movie file written in   scene_file_writer.py:527
                             '/my/path/media/videos/scene/1080p60/partial_movie_fi
                             les/CameraIssue/1433715038_3210132319_2428177
                             325.mp4'
                    INFO     Combining to Movie file.                      scene_file_writer.py:617
                    DEBUG    Partial movie files to combine (1 files):     scene_file_writer.py:561
                             ['/my/path/media/videos/scene/1080p60/partial_movie_f
                             iles/CameraIssue/1433715038_3210132319_242817
                             7325.mp4']
                    INFO                                                   scene_file_writer.py:736
                             File ready at
                             '/my/path/media/videos/scene/1080p60/CameraIssue.mp4'

                    INFO     Rendered CameraIssue                                      scene.py:241
                             Played 1 animations
                    INFO     Previewed File at:                                     file_ops.py:227
                             '/my/path/media/v
                             ideos/scene/1080p60/CameraIssue.mp4'

System specifications

System Details

• OS (with version, e.g., Windows 10 v2004 or macOS 10.15 (Catalina)): macOS 13.4 (Ventura)
• RAM: 16GB
• Python version (python/py/python3 --version): 3.11.4
• Installed modules (provide output from pip list):

Package                Version
---------------------- ---------
certifi                2022.9.24
chardet                3.0.4
charset-normalizer     3.2.0
click                  8.1.7
click-default-group    1.2.4
cloup                  0.13.1
colour                 0.1.5
Cython                 3.0.2
decorator              5.1.1
glcontext              2.4.0
googletrans            3.0.0
h11                    0.9.0
h2                     3.2.0
hpack                  3.0.0
hstspreload            2022.12.1
httpcore               0.9.1
httpx                  0.13.3
hyperframe             5.2.0
idna                   2.10
isosurfaces            0.1.0
manim                  0.17.3
ManimPango             0.4.3
mapbox-earcut          1.0.1
markdown-it-py         3.0.0
mdurl                  0.1.2
moderngl               5.8.2
moderngl-window        2.4.4
multipledispatch       1.0.0
networkx               2.8.8
numpy                  1.25.2
Pillow                 9.5.0
pip                    23.2.1
pycairo                1.24.0
pydub                  0.25.1
pygame                 2.5.1
pyglet                 2.0.9
Pygments               2.16.1
pyobjc-core            9.2
pyobjc-framework-Cocoa 9.2
pyrr                   0.10.3
requests               2.31.0
rfc3986                1.5.0
rich                   13.5.2
scipy                  1.11.2
screeninfo             0.8.1
setuptools             65.5.0
skia-pathops           0.7.4
sniffio                1.3.0
srt                    3.5.3
svgelements            1.9.6
tqdm                   4.66.1
urllib3                2.0.4
watchdog               2.3.1

LaTeX details

• LaTeX distribution (e.g. TeX Live 2020): MacTeX
• Installed LaTeX packages: Irrelevant; did not use LaTeX

FFMPEG

Output of ffmpeg -version:

ffmpeg version 6.0 Copyright (c) 2000-2023 the FFmpeg developers
built with Apple clang version 14.0.3 (clang-1403.0.22.14.1)
configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/6.0_1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
libavutil      58.  2.100 / 58.  2.100
libavcodec     60.  3.100 / 60.  3.100
libavformat    60.  3.100 / 60.  3.100
libavdevice    60.  1.100 / 60.  1.100
libavfilter     9.  3.100 /  9.  3.100
libswscale      7.  1.100 /  7.  1.100
libswresample   4. 10.100 /  4. 10.100
libpostproc    57.  1.100 / 57.  1.100

Additional comments

I have found that this issue persists without -qh in the command line arguments.

[DDQXZcp]

I also encountered this issue. If rotating two squares using self.camera.frame.animate.rotate, they are squished simultaneously.

Grouping all the objects and rotating works, but it is a bit tedious.

How to reproduce the issue

Code for reproducing the problem

%%manim -qm CircleToSquare

class CircleToSquare(MovingCameraScene):
    def construct(self):
        green_square = Square(color=GREEN, fill_opacity=0.8).move_to(2 * LEFT)
        red_square = Square(color=RED, fill_opacity=0.8).move_to(2 * RIGHT)

        self.play(Create(green_square))
        self.play(Create(red_square))
        self.wait()
        
        # Working
        all_objects = VGroup(green_square, red_square)
        self.play(all_objects.animate.rotate(PI/2))  # Rotate all objects by 90 degrees
        self.wait()

        # Not Working
        self.play(self.camera.frame.animate.rotate(PI*1/2))
        self.wait()
        self.play(self.camera.frame.animate.rotate(PI*1/2))
        self.wait()
        
        # Not Working
        self.play(Rotate(self.camera.frame, angle=2*PI, rate_func=linear),)
        self.wait()

Additional media files

Images/GIFs

CircleToSquare@2023-10-21@10-18-23.mp4

[wengkeii]

Hi, could I please be assigned to work on this issue?

I think that the unexpected behavior is caused by the default perspective projection of the camera, which distort objects when the camera is rotated.

I have been able to work around this issue using the following code as an example:

from manim import *

class CameraIssue(MovingCameraScene):
    def construct(self):
        square = Square()
        self.play(Create(square))
        self.wait(2)

        all_objects = VGroup(square)
        self.play(all_objects.animate.rotate(PI/2))
        self.wait(2)

In this code, I create a VGroup to group the objects and then apply the rotation to that group. This works as expected and rotates the objects without distortion.

However, I do acknowledge that this does not solve the issue from its root and this issue could possibly be caused by the frame rotation of the camera not being fully implemented yet as mentioned.

[DDQXZcp]

I am also trying to fix it. I think the frame rotation is not yet implemented I think? I found a TODO tag here moving_camera.py line 57.
This is what the structure looks like in my mind. I think the frame rotation should be independent of object rotation.

[amt1510]

class CameraSolution(MovingCameraScene):

def construct(self):
    s1 = Square()
    s2 = Square()
    s1.set_fill(RED, opacity=0.5).shift(2 * LEFT)
    s2.set_fill(GREEN, opacity=0.5).shift(2 * RIGHT)
    self.add(s1)
    self.add(s2)
    self.rotate_frame(PI / 2)

def rotate_frame(self, angle):
    all_objs = [
        obj for obj in self.mobjects if not isinstance(obj, ScreenRectangle)
    ]
    group = Group(*all_objs).set_x(0).arrange(buff=1.0)
    self.add(group)
    self.play(group.animate.rotate(angle))

This is what I have tried so far. It works for n objects but the code only works in Scene

[meawplex-plus]

Thank you, all. I had no idea that frame rotation was unfinished. I will look into the VGrouping/Custom self.camera.frame.animate.rotate methods.

[DDQXZcp]

I have some idea of what is going wrong. The video is a standard 16:9 rectangle, as well as the frame. If we rotate the frame, the frame height and width change (this is not expected, rotating the view should not affect height and width). Then the frame is auto-zoom to fit the video.

Here I rotate the frame by 1/4*pi, and the frame is expanded from (8.0, 14.222222222222221) to (15.713484026367722,
15.713484026367723). That is 16:9 -> 1:1. Then imagine a square frame is compressed back into a flat frame. That explains why the objects are squished vertically.

How to reproduce the issue

Code for reproducing the problem

%%manim -qm CircleToSquare

class CircleToSquare(MovingCameraScene):
    def construct(self):
        green_square = Square(color=GREEN, fill_opacity=0.8).move_to(2 * LEFT)
        red_square = Square(color=RED, fill_opacity=0.8).move_to(2 * RIGHT)

        self.play(Create(green_square))
        self.play(Create(red_square))
        self.wait()
        
        # Check frame shape
        print(self.camera.frame.height)
        print(self.camera.frame.width)
        
        # Rotate frame
        self.play(self.camera.frame.animate.rotate(PI*1/4))
        self.wait()
        
        # Check frame shape
        print(self.camera.frame.height)
        print(self.camera.frame.width)

It prints out

8.0
14.222222222222221
15.713484026367722
15.713484026367723

[DDQXZcp]

The camera frame rotation is working perfectly in 3D Scene. No manual grouping is needed. The animation is exactly the same as 2D.

Code for Alternative Solution

Code for Alternative Solution

%%manim -qm My3DScene

class My3DScene(ThreeDScene):
    def construct(self):
        # Create a rectangle
        green_square = Square(color=GREEN, fill_opacity=0.8).move_to(2 * LEFT+2 * DOWN)
        red_square = Square(color=RED, fill_opacity=0.8).move_to(2 * RIGHT + 2 * DOWN)
        blue_square = Square(color=BLUE, fill_opacity=0.8).move_to(2 * UP)
        self.play(Create(green_square), Create(red_square), Create(blue_square))
        self.wait()
        
        # Rotate the camera along theta
        self.move_camera(phi=0, theta=0)
        self.wait()
        self.move_camera(phi=0, theta=PI/2)
        self.wait()
        self.move_camera(phi=0, theta=PI)
        self.wait()
        self.move_camera(phi=0, theta=1.5*PI)
        self.wait()
        self.move_camera(phi=0, theta=-PI/2)
        self.wait()
        
        # Rotate the camera alogn phi
        self.move_camera(phi=PI/2, theta=-PI/2)
        self.wait()
        self.move_camera(phi=PI, theta=-PI/2)
        self.wait()
        self.move_camera(phi=1.5*PI, theta=-PI/2)
        self.wait()
        self.move_camera(phi=2*PI, theta=-PI/2)
        self.wait()
        self.move_camera(phi=0, theta=-PI/2)
        self.wait()

Additional media files

Images/GIFs

My3DScene@2023-10-27@05-26-29.mp4