matplotlib example kitti lidar (snippet)

Python matplotlib example 'kitti lidar'

Modules used in program:

import numpy as np
import os
import pykitti # install using pip install pykitti

python kitti lidar

Python matplotlib example: kitti lidar

"""
VISUALISE THE LIDAR DATA FROM THE KITTI DATASET

Based on the sample code from
    https://github.com/utiasSTARS/pykitti/blob/master/demos/demo_raw.py
And:
    http://stackoverflow.com/a/37863912

Contains two methods of visualizing lidar data interactively.
 - Matplotlib - very slow, and likely to crash, so only 1 out of every 100
                points are plotted.
              - Also, data looks VERY distorted due to auto scaling along
                each axis. (this could potentially be edited)
 - Mayavi     - Much faster, and looks nicer.
              - Preserves actual scale along each axes so items look
                recognizable
"""
import pykitti  # install using pip install pykitti
import os
import numpy as np

# Chose which visualization library to use:  "mayavi" or "matplotlib"
# VISLIB = "mayavi"
VISLIB = "matplotlib"

# Raw Data directory information
basedir = '/home/dodo_brain/kitti_data/'
date = '2011_09_26'
drive = '0005'

# Optionally, specify the frame range to load
# since we are only visualizing one frame, we will restrict what we load
# Set to None to use all the data
frame_range = range(150, 151, 1)

# Load the data
dataset = pykitti.raw(basedir, date, drive, frame_range)

# Load Lidar Data
dataset.load_velo()         # Each scan is a Nx4 array of [x,y,z,reflectance]

# Plot only the ith frame (out of what has been loaded)
i = 0
velo = dataset.velo[i]

if VISLIB == "mayavi":
    # Plot using mayavi -Much faster and smoother than matplotlib
    import mayavi.mlab

    fig = mayavi.mlab.figure(bgcolor=(0, 0, 0), size=(640, 360))
    mayavi.mlab.points3d(
        velo[:, 0],   # x
        velo[:, 1],   # y
        velo[:, 2],   # z
        velo[:, 2],   # Height data used for shading
        mode="point", # How to render each point {'point', 'sphere' , 'cube' }
        colormap='spectral',  # 'bone', 'copper',
        #color=(0, 1, 0),     # Used a fixed (r,g,b) color instead of colormap
        scale_factor=100,     # scale of the points
        line_width=10,        # Scale of the line, if any
        figure=fig,
    )
    # velo[:, 3], # reflectance values
    mayavi.mlab.show()

else:
    # Plot Using Matplotlib - Much slower than mayavi.
    # NOTE: Only 1 out of every 100 points are plotted using the matplotlib
    #       version to prevent crashing the computer
    import matplotlib.pyplot as plt
    from mpl_toolkits.mplot3d import Axes3D

    skip = 100 # plot one in every `skip` points

    fig = plt.figure()
    ax = fig.add_subplot(111, projection='3d')
    velo_range = range(0, velo.shape[0], skip) # skip points to prevent crash
    ax.scatter(velo[velo_range, 0],   # x
               velo[velo_range, 1],   # y
               velo[velo_range, 2],   # z
               c=velo[velo_range, 3], # reflectance
               cmap='gray')
    ax.set_title('Lidar scan (subsampled)')
    plt.show()

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