Skip to content

Running the Simulator

Run your autons on a computer and watch a replay, no robot needed. The simulator runs your real RW code with a simulated robot, sensors, and Override field, and writes a replay page showing where the robot really went next to where RW thought it was.

One-time setup: install a C++ compiler

Open Terminal and run:

xcode-select --install

The simulator runs in WSL (Linux inside Windows). Some school laptops block WSL.

  1. Open PowerShell as administrator, run this, and restart:

    wsl --install

  2. Finish the Ubuntu setup that opens

  3. In VS Code's terminal, type wsl. The terminal is now Linux, still in your project folder
  4. Run:
sudo apt update && sudo apt install -y g++

Install g++, e.g.:

sudo apt install g++

Run an auton

From the project folder (on Windows, type wsl in VS Code's terminal first):

sh sim/run-sim.sh "Async Example"

Use the name you gave addAuton(). To list them:

sh sim/run-sim.sh --list

It builds your current code (everything in src/ and custom/, minus src/vexcode/main.cpp), runs runPreAutonomous() and then your auton on a simulated robot, and writes a replay such as sim/out/Async-Example.html. In a PROS project it builds your src/ files and runs initialize() and autonomous() instead (see Using PROS).

Open the replay in any browser to play it back. In VS Code, right-click it and choose Reveal in Finder or Reveal in File Explorer, then double-click it. It shows the field, the path the robot really drove, the path RW thought it drove, and the error between them. The terminal prints the same summary.

Options

Option What it does
--list List the autons added with addAuton()
--start X,Y,HEADING Where the robot starts, in field-centered inches and compass degrees (default -35,-60,0). Use the same spot your auton assumes
--time SECONDS Stop after this long (default 15; use 60 for skills)
--ideal No wheel slip, IMU error, or sensor noise
--walls Empty field without Override's goals, loaders, and stacks
--size INCHES, --seed N, --out FILE Field size, random seed, and where to write the replay

What it simulates

  • Robot: your drive (tank, X-drive, mecanum or H-drive) with the measurements in robot-config.cpp (rw-config.cpp on PROS), with motor lag, wheel slip, turning scrub, and sideways skid. To match your robot exactly, calibrate it
  • Walls: the robot stops at the perimeter but its wheels keep spinning, so odometry drifts like it does on a real field
  • Sensors:
    • IMU with a small scale error and drift
    • tracking wheels
    • the four reset distance sensors, which update every 33 ms, lag about 40 ms, and see the walls, goals, loaders, and stacks
  • Code: all of your code runs unchanged, including threads, wait(), MCL, and the auton selector

Limitations

  • The robot drives through goals and game elements; only the walls stop it
  • Mechanisms just spin, controller inputs read as zero, and the Brain screen draws nothing
  • The SD card is the folder sim/out/sdcard. The Drive Calibration auton saves its log there if you give it time: --time 20
  • Distance sensors other than the four reset sensors read "nothing detected"

If your code uses a VEX or PROS function the simulator doesn't have yet, the build error names it. Add it to sim/vex/v5_vcs.h (sim/pros/pros-sim.h on PROS), or ask on Discord.