Fast, Real-time plotting of points using pyqtgraph and a LiDAR

Question

I want to create a real-time, point plotting GUI. I am using the Scanse Sweep LiDAR, and at each sweep of this LiDAR (working between 1 - 10Hz) I receive approximately 1000 points (x, y) describing the LiDARs surrounding. This is a 2D LiDAR.

I have looked everywhere and tried countless of code snippets for pyqtgraph, but either it crashes, is super slow or doesn't work at all.

Is there a straight-forward way of creating a plotter window and upon each new scan/data delivery, push those points to the plotter window?

Thankful for any kind of help

Answer 1

It is unclear to me what exactly you want to do, so I assume that you want to make a scatter plot with a 1000 points that are refreshed 10 times a second. Next time please include your code so that we can reproduce your issues and see what you want to achieve.

In my experience PyQtGraph is the fastest option in Python. It can easily plot a 1000 points at 10 Hz. See the example below.

#!/usr/bin/env python

from PyQt5 import QtCore, QtWidgets
import pyqtgraph as pg
import numpy as np


class MyWidget(pg.GraphicsWindow):

    def __init__(self, parent=None):
        super().__init__(parent=parent)

        self.mainLayout = QtWidgets.QVBoxLayout()
        self.setLayout(self.mainLayout)

        self.timer = QtCore.QTimer(self)
        self.timer.setInterval(100) # in milliseconds
        self.timer.start()
        self.timer.timeout.connect(self.onNewData)

        self.plotItem = self.addPlot(title="Lidar points")

        self.plotDataItem = self.plotItem.plot([], pen=None, 
            symbolBrush=(255,0,0), symbolSize=5, symbolPen=None)


    def setData(self, x, y):
        self.plotDataItem.setData(x, y)


    def onNewData(self):
        numPoints = 1000  
        x = np.random.normal(size=numPoints)
        y = np.random.normal(size=numPoints)
        self.setData(x, y)


def main():
    app = QtWidgets.QApplication([])

    pg.setConfigOptions(antialias=False) # True seems to work as well

    win = MyWidget()
    win.show()
    win.resize(800,600) 
    win.raise_()
    app.exec_()

if __name__ == "__main__":
    main()

The way it works is as follows. By plotting an empty list a PlotDataItem is created. This represents a collection of points. When new data points arrive, the setData method is used to set them as the data of the PlotDataItem, which removes the old points.