line.put_start_and_end_on()

[juanwinograd]

Description of bug / unexpected behavior

line method put_start_and_end_on(start,end) raises an excpetion when start == end

Expected behavior

I think it should just draw one point

How to reproduce the issue

Code for reproducing the problem

line = DashedLine(np.zeros(3),np.zeros(3))
line.put_start_and_end_on(np.zeros(3),np.array([1,0,0]))

System specifications

System Details

• OS (with version, e.g., Windows 10 v2004 or macOS 10.15 (Catalina)): Windows 10
• RAM: 8GB
• Python version (python/py/python3 --version): 3.10.8
• Installed modules (provide output from pip list):

appdirs                1.4.4
asttokens              2.1.0
attrs                  18.2.0
backcall               0.2.0
certifi                2022.9.24
charset-normalizer     2.1.1
click                  8.1.3
click-default-group    1.2.2
cloup                  0.13.1
colorama               0.4.6
colour                 0.1.5
commonmark             0.9.1
contourpy              1.0.6
cycler                 0.11.0
debugpy                1.6.3
decorator              5.1.1
entrypoints            0.4
et-xmlfile             1.1.0
executing              1.2.0
fonttools              4.38.0
glcontext              2.3.7
idna                   3.4
imageio                2.27.0
ipykernel              6.17.1
ipython                8.6.0
isosurfaces            0.1.0
jedi                   0.18.2
jupyter_client         7.4.7
jupyter_core           5.0.0
kiwisolver             1.4.4
manim                  0.17.2
manim-fonts            0.2.0
ManimPango             0.4.2
mapbox-earcut          1.0.1
matplotlib             3.6.2
matplotlib-inline      0.1.6
matplotlib-label-lines 0.6.0
moderngl               5.7.2
moderngl-window        2.4.2
more-itertools         10.0.0
multipledispatch       0.6.0
nest-asyncio           1.5.6
networkx               2.8.8
numpy                  1.23.5
openpyxl               3.0.10
ordered-set            4.1.0
packaging              21.3
pandas                 1.5.2
parso                  0.8.3
pdflatex               0.1.3
pickleshare            0.7.5
Pillow                 9.3.0
pip                    23.2.1
platformdirs           2.5.4
prompt-toolkit         3.0.33
psutil                 5.9.4
pure-eval              0.2.2
pycairo                1.22.0
pydub                  0.25.1
pyglet                 2.0.0
Pygments               2.13.0
PyLaTeX                1.4.1
pyparsing              3.0.9
pyrr                   0.10.3
python-dateutil        2.8.2
pytz                   2022.6
pywin32                305
pyzmq                  24.0.1
requests               2.28.1
rich                   12.6.0
scipy                  1.9.3
screeninfo             0.8.1
setuptools             63.2.0
six                    1.16.0
skia-pathops           0.7.4
srt                    3.5.2
stack-data             0.6.1
svgelements            1.9.0
tornado                6.2
tqdm                   4.64.1
traitlets              5.5.0
typing_extensions      4.5.0
urllib3                1.26.13
watchdog               2.1.9
wcwidth                0.2.5
wheel                  0.38.4```
</details>

[MrDiver]

Maybe attaching a screenshot would be a good idea!

[MrDiver]

╭───────────────────── Traceback (most recent call last) ──────────────────────╮
│ /usr/local/lib/python3.8/site-packages/manim/cli/render/commands.py:115 in   │
│ render                                                                       │
│                                                                              │
│   112 │   │   │   try:                                                       │
│   113 │   │   │   │   with tempconfig({}):                                   │
│   114 │   │   │   │   │   scene = SceneClass()                               │
│ ❱ 115 │   │   │   │   │   scene.render()                                     │
│   116 │   │   │   except Exception:                                          │
│   117 │   │   │   │   error_console.print_exception()                        │
│   118 │   │   │   │   sys.exit(1)                                            │
│                                                                              │
│ /usr/local/lib/python3.8/site-packages/manim/scene/scene.py:223 in render    │
│                                                                              │
│    220 │   │   """                                                           │
│    221 │   │   self.setup()                                                  │
│    222 │   │   try:                                                          │
│ ❱  223 │   │   │   self.construct()                                          │
│    224 │   │   except EndSceneEarlyException:                                │
│    225 │   │   │   pass                                                      │
│    226 │   │   except RerunSceneException as e:                              │
│                                                                              │
│ /manim/script.py:5 in construct                                              │
│                                                                              │
│   2 class Manimation(Scene):                                                 │
│   3 │   def construct(self):                                                 │
│   4 │     line = DashedLine(np.zeros(3),np.zeros(3))                         │
│ ❱ 5 │     line.put_start_and_end_on(np.zeros(3),np.array([1,0,0]))           │
│   6                                                                          │
│                                                                              │
│ /usr/local/lib/python3.8/site-packages/manim/mobject/geometry/line.py:146 in │
│ put_start_and_end_on                                                         │
│                                                                              │
│    143 │   │   │   self.start = start                                        │
│    144 │   │   │   self.end = end                                            │
│    145 │   │   │   self.generate_points()                                    │
│ ❱  146 │   │   return super().put_start_and_end_on(start, end)               │
│    147 │                                                                     │
│    148 │   def get_vector(self):                                             │
│    149 │   │   return self.get_end() - self.get_start()                      │
│                                                                              │
│ /usr/local/lib/python3.8/site-packages/manim/mobject/mobject.py:1669 in      │
│ put_start_and_end_on                                                         │
│                                                                              │
│   1666 │   │   curr_start, curr_end = self.get_start_and_end()               │
│   1667 │   │   curr_vect = curr_end - curr_start                             │
│   1668 │   │   if np.all(curr_vect == 0):                                    │
│ ❱ 1669 │   │   │   raise Exception("Cannot position endpoints of closed loop │
│   1670 │   │   target_vect = np.array(end) - np.array(start)                 │
│   1671 │   │   axis = (                                                      │
│   1672 │   │   │   normalize(np.cross(curr_vect, target_vect))               │
╰──────────────────────────────────────────────────────────────────────────────╯
Exception: Cannot position endpoints of closed loop

[MrDiver]

I think instead of drawing a point it should draw nothing, because you're trying to convince multiple lines to be in the same singular spot which is not really possible to draw because a line needs a direction.

[juanwinograd]

It's a good option too.

I was drawing a DashedLine from some point to the axes and then updating the line as the point moves. So, both options would work for me. The line should disappear just a moment while the dot cross the axis and reappear in the next frame.