PSE Traffic Simulation Visualizer

Script to easily visualize traffic simulations (made for the PSE course) via plain text data output.

Requirements

This script requires Python 3 and Pygame.

Tested with:

Python 3.8.10
Pygame 2.1.2
Ubuntu 20.04

You can install Pygame using pip3 install pygame or similar.

Usage

The script reads its data from stdin before launching the visualization. The text data format is described below.

You can use the following command to pipe the output of your simulation to the visualizer (assuming ./trafficsimulation runs the simulation and writes its output to stdout):

./trafficsimulation | python3 visualize.py

Use --help to get an overview of all available options:

usage: visualize.py [-h] [-s SPEED] [--dark]

Traffic Simulation Visualizer

optional arguments:
  -h, --help            show this help message and exit
  -s SPEED, --speed SPEED
                        set the playback rate to the given factor (>= 1)
  --dark                use dark mode

Additional settings can be configured in the script (initial window dimensions, custom colors, etc.).

Controls

Press space to toggle play/pause
When paused, press (or hold down)
- ← to step one frame backward
- → to step one frame forward
Hold shift while doing the above to step by the configured speed
Press r to reset the visualization to the first frame

Data format

The visualizer reads the data from stdin line by line, where each line should contain the next simulation ‘frame’. Here is an example of what such a frame should look like:

{
  "time": 0.0166,
  "roads": [
    {
      "name": "Arcade Street",
      "length": 500,
      "cars": [ {"x": 20}, {"x": 0} ],
      "lights": [ {"x": 300, "green": 0, "xs": 50, "xs0", 15} ]
    },
    {
      "name": "Gold Avenue",
      "length": 400,
      "cars": [ {"x": 0} ],
      "lights": [ {"x": 200, "green": 0, "xs": 50, "xs0": 15} ]
    }
  ]
}

Note that each frame should be on its own single line. The example is split over multiple lines for readability only.

The "time" is the current frame’s ‘timestamp’. For now, it is only shown but has no further semantic value. The "x" in cars and traffic lights are their positions. And "green" tells the current color of a certain traffic light: 1 means green, 0 means red. "xs" is the deceleration distance and "xs0" is the stopping distance before the traffic light. Both "xs" and "xs0" are optional, but the other will be ignored if one of them is left out.