Changing position of vertical (z) axis of 3D plot (Matplotlib)?

Question

I'm doing some 3D surface plots using Matplotlib in Python and have noticed an annoying phenomenon. Depending on how I set the viewpoint (camera location), the vertical (z) axis moves between the left and right side. Here are two examples: Example 1, Axis left, Example 2, Axis right. The first example has ax.view_init(25,-135) while the second has ax.view_init(25,-45).

I would like to keep the viewpoints the same (best way to view the data). Is there any way to force the axis to one side or the other?

Answer 1

I needed something similar: drawing the zaxis on both sides. Thanks to the answer by @crayzeewulf I came to following workaround (for left, righ, or both sides):

First plot your 3d as you need, then before you call show() wrap the Axes3D with a Wrapper class that simply overrides the draw() method.

The Wrapper Class calls simply sets the visibility of some features to False, it draws itself and finally draws the zaxis with modified PLANES. This Wrapper Class allows you to draw the zaxis on the left, on the rigth or on both sides.

import matplotlib
matplotlib.use('QT4Agg')
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import axes3d

class MyAxes3D(axes3d.Axes3D):

    def __init__(self, baseObject, sides_to_draw):
        self.__class__ = type(baseObject.__class__.__name__,
                              (self.__class__, baseObject.__class__),
                              {})
        self.__dict__ = baseObject.__dict__
        self.sides_to_draw = list(sides_to_draw)
        self.mouse_init()

    def set_some_features_visibility(self, visible):
        for t in self.w_zaxis.get_ticklines() + self.w_zaxis.get_ticklabels():
            t.set_visible(visible)
        self.w_zaxis.line.set_visible(visible)
        self.w_zaxis.pane.set_visible(visible)
        self.w_zaxis.label.set_visible(visible)

    def draw(self, renderer):
        # set visibility of some features False 
        self.set_some_features_visibility(False)
        # draw the axes
        super(MyAxes3D, self).draw(renderer)
        # set visibility of some features True. 
        # This could be adapted to set your features to desired visibility, 
        # e.g. storing the previous values and restoring the values
        self.set_some_features_visibility(True)

        zaxis = self.zaxis
        draw_grid_old = zaxis.axes._draw_grid
        # disable draw grid
        zaxis.axes._draw_grid = False

        tmp_planes = zaxis._PLANES

        if 'l' in self.sides_to_draw :
            # draw zaxis on the left side
            zaxis._PLANES = (tmp_planes[2], tmp_planes[3],
                             tmp_planes[0], tmp_planes[1],
                             tmp_planes[4], tmp_planes[5])
            zaxis.draw(renderer)
        if 'r' in self.sides_to_draw :
            # draw zaxis on the right side
            zaxis._PLANES = (tmp_planes[3], tmp_planes[2], 
                             tmp_planes[1], tmp_planes[0], 
                             tmp_planes[4], tmp_planes[5])
            zaxis.draw(renderer)

        zaxis._PLANES = tmp_planes

        # disable draw grid
        zaxis.axes._draw_grid = draw_grid_old

def example_surface(ax):
    """ draw an example surface. code borrowed from http://matplotlib.org/examples/mplot3d/surface3d_demo.html """
    from matplotlib import cm
    import numpy as np
    X = np.arange(-5, 5, 0.25)
    Y = np.arange(-5, 5, 0.25)
    X, Y = np.meshgrid(X, Y)
    R = np.sqrt(X**2 + Y**2)
    Z = np.sin(R)
    surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, cmap=cm.coolwarm, linewidth=0, antialiased=False)

if __name__ == '__main__':
    fig = plt.figure(figsize=(15, 5))
    ax = fig.add_subplot(131, projection='3d')
    ax.set_title('z-axis left side')
    ax = fig.add_axes(MyAxes3D(ax, 'l'))
    example_surface(ax) # draw an example surface
    ax = fig.add_subplot(132, projection='3d')
    ax.set_title('z-axis both sides')
    ax = fig.add_axes(MyAxes3D(ax, 'lr'))
    example_surface(ax) # draw an example surface
    ax = fig.add_subplot(133, projection='3d')
    ax.set_title('z-axis right side')
    ax = fig.add_axes(MyAxes3D(ax, 'r'))
    example_surface(ax) # draw an example surface
    plt.show()

Answer 2

As pointed out in a comment below by OP, the method suggested below did not provide adequate answer to the original question.

As mentioned in this note, there are lots of hard-coded values in axis3d that make it difficult to customize its behavior. So, I do not think there is a good way to do this in the current API. You can "hack" it by modifying the _PLANES parameter of the zaxis as shown below:

tmp_planes = ax.zaxis._PLANES 
ax.zaxis._PLANES = ( tmp_planes[2], tmp_planes[3], 
                     tmp_planes[0], tmp_planes[1], 
                     tmp_planes[4], tmp_planes[5])
view_1 = (25, -135)
view_2 = (25, -45)
init_view = view_2
ax.view_init(*init_view)

Now the z-axis will always be on the left side of the figure no matter how you rotate the figure (as long as positive-z direction is pointing up). The x-axis and y-axis will keep flipping though. You can play with _PLANES and might be able to get the desired behavior for all axes but this is likely to break in future versions of matplotlib.