3D Plot Projection Types

Introduction

This lab demonstrates the different camera projections for 3D plots, and the effects of changing the focal length for a perspective projection using Python Matplotlib.

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Import Libraries

First, import the necessary libraries, including Matplotlib and Axes3D from mpl_toolkits.mplot3d.

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import axes3d

Get Data

Get the test data for the 3D plot.

X, Y, Z = axes3d.get_test_data(0.05)

Create a Figure with Subplots

Create a figure with three subplots using plt.subplots.

fig, axs = plt.subplots(1, 3, subplot_kw={'projection': '3d'})

Plot the Data

Plot the data on each of the three subplots using plot_wireframe.

for ax in axs:
    ax.plot_wireframe(X, Y, Z, rstride=10, cstride=10)

Set the Orthographic Projection

Set the first subplot to use an orthographic projection with a FOV of 0 degrees and a focal_length of infinity.

axs[0].set_proj_type('ortho')  ## FOV = 0 deg
axs[0].set_title("'ortho'\nfocal_length = ∞", fontsize=10)

Set the Perspective Projections

Set the second subplot to use a perspective projection with the default FOV of 90 degrees and a focal_length of 1.

axs[1].set_proj_type('persp')  ## FOV = 90 deg
axs[1].set_title("'persp'\nfocal_length = 1 (default)", fontsize=10)

Set the third subplot to use a perspective projection with a FOV of 157.4 degrees and a focal_length of 0.2.

axs[2].set_proj_type('persp', focal_length=0.2)  ## FOV = 157.4 deg
axs[2].set_title("'persp'\nfocal_length = 0.2", fontsize=10)

Show the Plot

Display the plot using plt.show().

plt.show()

Summary

This lab demonstrated how to create a 3D plot using Python Matplotlib and how to change the projection type and focal length of the plot. The orthographic projection flattens the image while the perspective projection exaggerates the perspective and gives the image more apparent depth. The default focal length of 1 corresponds to a Field of View (FOV) of 90 deg.