3D plot aspect ratio [matplotlib]

Question

I am using the code written here to make a plot like this one below.

The problem is, that I want to adjust an aspect ratio, namely, to stretch it along the z-axis, so that all the stacked images are more or less visible. Is there an easy way of doing that?

Answer 1

Looks like there is no “proper” way to do it, but we can try monkey-patching our way around the problem. Here’s the best kludge I could do:

from mpl_toolkits.mplot3d import proj3d

def make_get_proj(self, rx, ry, rz):
    '''
    Return a variation on :func:`~mpl_toolkit.mplot2d.axes3d.Axes3D.getproj` that
    makes the box aspect ratio equal to *rx:ry:rz*, using an axes object *self*.
    '''

    rm = max(rx, ry, rz)
    kx = rm / rx; ky = rm / ry; kz = rm / rz;

    # Copied directly from mpl_toolkit/mplot3d/axes3d.py. New or modified lines are
    # marked by ##
    def get_proj():
        relev, razim = np.pi * self.elev/180, np.pi * self.azim/180

        xmin, xmax = self.get_xlim3d()
        ymin, ymax = self.get_ylim3d()
        zmin, zmax = self.get_zlim3d()

        # transform to uniform world coordinates 0-1.0,0-1.0,0-1.0
        worldM = proj3d.world_transformation(xmin, xmax,
                                             ymin, ymax,
                                             zmin, zmax)

        # adjust the aspect ratio                          ##
        aspectM = proj3d.world_transformation(-kx + 1, kx, ##
                                              -ky + 1, ky, ##
                                              -kz + 1, kz) ##

        # look into the middle of the new coordinates
        R = np.array([0.5, 0.5, 0.5])

        xp = R[0] + np.cos(razim) * np.cos(relev) * self.dist
        yp = R[1] + np.sin(razim) * np.cos(relev) * self.dist
        zp = R[2] + np.sin(relev) * self.dist
        E = np.array((xp, yp, zp))

        self.eye = E
        self.vvec = R - E
        self.vvec = self.vvec / proj3d.mod(self.vvec)

        if abs(relev) > np.pi/2:
            # upside down
            V = np.array((0, 0, -1))
        else:
            V = np.array((0, 0, 1))
        zfront, zback = -self.dist, self.dist

        viewM = proj3d.view_transformation(E, R, V)
        perspM = proj3d.persp_transformation(zfront, zback)
        M0 = np.dot(viewM, np.dot(aspectM, worldM)) ##
        M = np.dot(perspM, M0)
        return M
    return get_proj

# and later in the code:
ax.get_proj = make_get_proj(ax, 1, 1, 2)
ax.set_aspect(1.0)

Answer 2

As of matplotlib 3.3.0, Axes3D.set_box_aspect seems to be the recommended approach.

import matplotlib.pyplot as plt

ax = plt.axes(projection='3d')

N = 10  # some number > 1 that stretches z axis as you desire
ax.set_box_aspect((1, 1, N))  # xy aspect ratio is 1:1, but stretches z axis