8000 Fix mplot3d projection by eric-wieser · Pull Request #8896 · matplotlib/matplotlib · GitHub
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Fix mplot3d projection #8896

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Merged
merged 9 commits into from
Feb 7, 2020
Merged

Fix mplot3d projection #8896

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64f197b
BUG: Fix the aspect ratio of 3d plots
eric-wieser Mar 28, 2019
c765493
Update images from the changes in the previous commit
Mar 28, 2019
58e961d
ENH: Set the default plotbox aspect to match how renders looked previ…
eric-wieser Mar 28, 2019
c95fea3
Update images from the changes in the previous commit
Mar 28, 2019
c641607
TST: Change tests to use default styles
eric-wieser Jun 24, 2019
7f1732e
Update images from the changes in the previous commit
Jun 24, 2019
e601965
Update 2019-03-25-mplot3d-projection.rst
eric-wieser Oct 23, 2019
0848bd1
Merge branch 'master' into fix-mplot3d-projection
eric-wieser Dec 3, 2019
0492b88
Fix baseline images and whatsnew note.
anntzer Dec 14, 2019
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BUG: Fix the aspect ratio of 3d plots 
Fixes gh-8894, by always using a "position" that maintains a uniform coordinate system.

Test added - when viewed from above, the plot should be square not rhombic.
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@eric-wieser
eric-wieser committed Jun 24, 2019
commit 64f197b9269a141991e8370865231804d4aa19eb
5 changes: 5 additions & 0 deletions doc/users/next_whats_new/2019-03-25-mplot3d-projection.rst
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@@ -0,0 +1,5 @@
``Axes3D`` now preserves right angles when rotating
---------------------------------------------------

:class:`~mpl_toolkits.mplot3d.Axes3D` no longer stretches the plot in the x
axis after projecting.
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This is a bit misleading. It isn't always a stretch in the x axis. Look at some of the image diffs, particularly the bar3d rotated one, and sometimes the stretching was in other directions. This is also misleading to some users because they may not be explicitly rotating the figure, but this still impacts them. This impacts just about anybody who has used mplot3d.

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It's a stretch in the window x axis (ie, the axis used after projection). You're right though, the wording is bad.

6 changes: 3 additions & 3 deletions lib/matplotlib/axes/_base.py
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Expand Up @@ -1467,9 +1467,9 @@ def apply_aspect(self, position=None):
"""
Adjust the Axes for a specified data aspect ratio.

Depending on `.get_adjustable` this will modify either the Axes box
(position) or the view limits. In the former case, `.get_anchor`
will affect the position.
Depending on `.get_adjustable` this will modify either the
Axes box (position) or the view limits. In the former case,
`~matplotlib.axes.Axes.get_anchor` will affect the position.

Notes
-----
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14 changes: 14 additions & 0 deletions lib/mpl_toolkits/mplot3d/axes3d.py
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Expand Up @@ -265,6 +265,20 @@ def tunit_edges(self, vals=None, M=None):
(tc[7], tc[4])]
return edges

def apply_aspect(self, position=None):
if position is None:
position = self.get_position(original=True)

# in the superclass, we would go through and actually deal with axis
# scales and box/datalim. Those are all irrelevant - all we need to do
# is make sure our coordinate system is square.
figW, figH = self.get_figure().get_size_inches()
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Why use the figure's aspect ratio? What if the figure has 3 subplots all in a row?

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@eric-wieser eric-wieser Aug 2, 2017 •
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Because all sizes in matplotlib are relative to the figure. pb.shrunk_to_aspect seems to take the ratio of the top-level parent (the figure), and the desired ratio. This is because the end result is the size relative to the parent, as all objects in matplotlib seem to be sized - so to ensure a given aspect ratio, you need to account for that of the parent

Note that this is the same as the normal aspect=equal code, so is presumably correct.

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Ping @efiring, as I think you are the resident expert on all the ways this could possibly go wrong.

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I think it makes sense. I have no intention of spending the time required to understand mplot3d well enough to make a detailed review, but in the absence of any such review I am inclined to trust that this PR is a major improvement, as it appears to be fixing a basic design flaw.

fig_aspect = figH / figW
box_aspect = 1
pb = position.frozen()
pb1 = pb.shrunk_to_aspect(box_aspect, pb, fig_aspect)
self.set_position(pb1.anchored(self.get_anchor(), pb), 'active')

@artist.allow_rasterization
def draw(self, renderer):
# draw the background patch
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7 changes: 7 additions & 0 deletions lib/mpl_toolkits/tests/test_mplot3d.py
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Expand Up @@ -478,6 +478,13 @@ def test_axes3d_cla():
ax.cla() # make sure the axis displayed is 3D (not 2D)


@image_comparison(['axes3d_rotated.png'])
def test_axes3d_rotated():
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1, projection='3d')
ax.view_init(90, 45) # look down, rotated. Should be square


def test_plotsurface_1d_raises():
x = np.linspace(0.5, 10, num=100)
y = np.linspace(0.5, 10, num=100)
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