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add third angle to view_init() #14453
Description
Bug report
Bug summary
mpl_toolkits.mplot3d.axes3d.Axes3D.view_init
provides a means to set the elevation and the azimuth, but the z-axis is always aligned with the vertical camera axis.
A third angle would be required to permit any view.
The issue was reported on stackoverflow 3.5 years ago.
Code for reproduction
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = Axes3D(fig)
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')
plt.show()Actual outcome
Now, however hard you try to rotate the plot interactively or what angles you set in ax.view_init(), you will never be able to get the z-axis in a horizontalish position that is required to produce the plot below:
Expected outcome
By rotating interactively or via ax.view_init() one should be able to obtain this view below. Unfortunately, this is not possible.
Matplotlib version
- Operating system: Ubuntu 16.04
- Matplotlib version: 3.1.0, py37h5429711_0
- Matplotlib backend: Qt5Agg
- Python version: 3.7.3 (conda)
Activity
SReich-EMI commented on Mar 10, 2021
my searching of how this could work ends here. I would kindly ask the community to implement this third angle to complete the 3D plotting in this case.
WeatherGod commented on Mar 10, 2021
scottshambaugh commented on Oct 21, 2021
This is something I've been frustrated with pretty much every single time I need to plot something in 3D, and I'm going to take a stab at it this weekend and see how far I can get.
The missing piece is that azimuth, elevation, and radius uniquely define a viewpoint in 3D space, but you need an additional angle defining the rotation about the radius vector in order to fully capture the entire space of view orientations. If we add this 3rd angle with a default value of 0 deg, it should not break any old code.
As to naming this additional angle, I think roll is the obvious choice. It aligns with both the aerospace pith/yaw/roll convention, as well as the camera angle pan/tilt/roll convention. On the other hand I have seen tilt, twist, lean, and bank used for this angle, so if someone has a strong opinion or a source for the canonical term used in computer graphics I'm open to that. We will be jumping ahead of matlab features a bit, so if they decide to add this in the future and choose a different name there is the risk of divergence.
Really this should be done using quaternions - Euler angles are pretty much always bad. But since quaternions aren't natively in numpy we probably don't want to introduce those as a dependency just to avoid gimbal lock at the two poles.
scottshambaugh commented on Oct 21, 2021
This looks like a relevant PR to keep in mind when reworking this: #10762
timhoffm commented on Oct 21, 2021
There are two aspects to consider:
With three angles, you have to find a reasonable execution order and document that.
scottshambaugh commented on Oct 22, 2021
Finished my PR, it's ready for review.
baloe commented on Dec 3, 2021
This is brilliant, thank you so much @scottshambaugh !
baloe commented on Dec 3, 2021
I updated my answer in the SO thread: https://stackoverflow.com/a/56457693/7042795
SReich-EMI commented on Dec 6, 2021
Thanks a lot for your work! I will surely test it in the next days!