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patquem opened this issue Feb 28, 2022 · 4 comments · Fixed by #23409
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[ENH]: Provide axis('equal') for Axes3D. #22570

patquem opened this issue Feb 28, 2022 · 4 comments · Fixed by #23409
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New feature topic: mplot3d topic: ticks axis labels
Milestone
v3.6.0

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@patquem
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patquem commented Feb 28, 2022

Bug summary

In the example below, I wish to observe a unitary 3D cube in its diagonal axis (1, 1, 1).
azimut and elevation angle should be both 45°, normally.
Why do I need to set elevation = 28° ????
Thanks,
Patrick

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots(1, 3, figsize=(15, 5),
                       subplot_kw=dict(projection="3d",
                                       proj_type='ortho'))

ax[0].voxels(np.ones((1, 1, 1)), facecolors=[0, 0, 0, 0], edgecolors='k')
ax[0].quiver(0, 0, 0, 1, 1, 1, color='r', linewidth=5)

ax[1].set_title("azim=45°, elev=45°")
ax[1].voxels(np.ones((1, 1, 1)), facecolors=[0, 0, 0, 0], edgecolors='k')
ax[1].view_init(azim=45, elev=45)
ax[1].quiver(0, 0, 0, 1, 1, 1, color='r', linewidth=5)

ax[2].set_title("azim=45°, elev=28°")
ax[2].voxels(np.ones((1, 1, 1)), facecolors=[0, 0, 0, 0], edgecolors='k')
ax[2].view_init(azim=45, elev=28)
ax[2].quiver(0, 0, 0, 1, 1, 1, color='r', linewidth=5)

plt.show()

Actual outcome

image

Expected outcome

view_init(azim=45, elev=45) and not view_init(azim=45, elev=28) to have the expected 3D representation

Additional information

No response

Operating system

Windows

Matplotlib Version

3.4.2

Matplotlib Backend

No response

Python version

Python 3.7.7

Jupyter version

No response

Installation

pip
@oscargus
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oscargus commented Feb 28, 2022 •
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Ideally, it should be possible to do ax[1].axis('equal') to obtain what you are looking for (see https://matplotlib.org/stable/gallery/subplots_axes_and_figures/axis_equal_demo.html). However, Axes3D does not (yet) support that:

Traceback (most recent call last):

  Input In [18] in <module>
    ax[1].axis('equal')

  File /local/data1/miniconda3/lib/python3.8/site-packages/matplotlib/axes/_base.py:2047 in axis
    self.set_aspect('equal', adjustable='datalim')

  File /local/data1/miniconda3/lib/python3.8/site-packages/mpl_toolkits/mplot3d/axes3d.py:311 in set_aspect
    raise NotImplementedError(

NotImplementedError: Axes3D currently only supports the aspect argument 'auto'. You passed in 'equal'.

So, basically, there is a different scaling for the z-axis compared to the x- and y-axes. You can see that from the grid blocks being rectangles (rather than squares, as for the bottom surface).

@oscargus oscargus changed the title [Bug]: elevation angle not correct with view_init() ? [ENH]: Provide axis('equal') for Axes3D. Feb 28, 2022
@oscargus
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You can get a bit closer by using: ax[1].set_box_aspect((4, 4, 4)), but it is still not exact. (Of course, you can probably find a better value for the last number, but that is about as bad as 28 degrees...) Now it at least looks like a cube.

@patquem
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patquem commented Feb 28, 2022 •
edited
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Hi @oscargus,
Thanks for your reply.
using ax[1].set_box_aspect((1, 1, 1)), the elevation angle is now 35°.
That is the correct elevation angle (atan(1/sqrt(2) ~35°) and not 45° as I have previously written.
Thanks.

@patquem patquem mentioned this issue Mar 25, 2022
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@patquem patquem mentioned this issue May 9, 2022
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@scottshambaugh scottshambaugh mentioned this issue Jul 9, 2022
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@jondo
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jondo commented Aug 2, 2022

B.t.w., this is a successor of #1077.

@QuLogic QuLogic added this to the v3.6.0 milestone Aug 3, 2022
@liuzhenqi77 liuzhenqi77 mentioned this issue Nov 17, 2022
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New feature topic: mplot3d topic: ticks axis labels
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