Qbr

Qbr, pronounced as Cuber, is a webcam-based 3x3x3 rubik's cube solver written in Python 3 and OpenCV.

• 🌈 Accurate color detection
• 🔍 Accurate 3x3x3 rubik's cube detection
• 🔠 Multilingual

Solve mode

Calibrate mode

Isn't the default color detection working out for you? Use the calibrate mode to let Qbr be familiar with your cube's color scheme. If your room has proper lighting then this will give you a 99.9% guarantee that your colors will be detected properly.

Simply follow the on-screen instructions and you're ready to go.

Table of Contents

• Qbr
  • Solve mode
  • Calibrate mode
• Table of Contents
• Introduction
• Installation
• Usage
  • The first 9-sticker display (upper left corner)
  • The second 9-sticker display (upper left corner)
  • Amount of sides scanned - text (bottom left corner)
  • Full 2D cube state visualization (bottom right corner)
  • Interface language (top right corner)
  • Calibrate mode
• Getting the solution
  • How to scan your cube properly?
• Keybindings
• Parameters
• Example runs
• Inspirational sources
• License

Introduction

The idea to create this came personally to mind when I started solving rubik's cubes. There were already so many professional programmers around the world who created robots that solve a rubik's cube in an ETA of 5 seconds and since 2016 in 1 second (link). That inspired me to create my own. I started using images only and eventually switched to webcam.

Installation

For linux users, make sure to install the following prerequisites:

$ sudo apt-get install python3-dev build-essential

Then, continue to install the project:

$ git clone --depth 1 https://github.com/kkoomen/qbr.git
$ cd qbr
$ python3 -m venv env
$ source ./env/bin/activate
$ pip3 install -r requirements.txt

Usage

Make sure you run source ./env/bin/activate every time you want to run the program.

Run Qbr:

$ ./src/qbr.py

This opens a webcam interface with the following things:

The first 9-sticker display (upper left corner)

This is live preview mode displaying the detected colors.

The second 9-sticker display (upper left corner)

This is the snapshot state. When pressing SPACE it will create a snapshot in order to show you what state it has saved. You can press SPACE as many times as you'd like if it has been detected wrong. The center piece color is used to detect which side to save.

Amount of sides scanned - text (bottom left corner)

The bottom left corner shows the amount of sides scanned. This is so you know if you've scanned in all sides before pressing ESC.

Full 2D cube state visualization (bottom right corner)

This visualization represents the whole cube state that is being saved and can be used to confirm whether the whole cube state has been scanned successfully.

Interface language (top right corner)

In the top right corner you can see the current interface language. If you want to change the interface language you can press l to cycle through them. Continue to press l until you've found the right language.

Default language is set to English.

Available languages are:

• English
• Hungarian
• Deutsch
• French
• Spanish
• Dutch
• 简体中文
• 台灣繁體中文

Calibrate mode

The default color scheme contains the most prominent colors for white, yellow, red, orange, blue and green. If this can't detect your cube its colors properly then you can use calibrate mode.

Press c to go into calibrate mode in order to let Qbr be familiar with your cube's color scheme. Simply follow the on-screen instructions and you're ready to go.

Note: Your calibrated settings are automatically saved after you've calibrated your cube successfully. The next time you start Qbr it will automatically load it.

Tip: If you've scanned wrong, simple go out of calibrate mode by pressing c and go back into calibrate by pressing c again.

Getting the solution

Qbr checks if you have filled in all 6 sides when pressing ESC. If so, it'll calculate a solution if you've scanned it correctly.

You should now see a solution (or an error if you did it wrong).

How to scan your cube properly?

There is a strict way of scanning in the cube. Qbr will detect the side automatically, but the way you rotate the cube during the time you're scanning it is crucial in order for Qbr to properly calculate a solution. Make sure to follow the steps below properly:

• Start off with the green side facing the camera and white on top, green being away from you. Start by scanning in the green side at this point.
• After you've scanned in the green side, rotate the cube 90 or -90 degrees horizontally. It doesn't matter if you go clockwise or counter-clockwise. Continue to do this for the green, blue, red and orange sides until you are back at the green side.
• You should now be in the same position like you started, having green facing the camera and white on top. Rotate the cube forward 90 degrees, resulting in green at the bottom and white facing the camera. Start scanning in the white side.
• After you've scanned the white side, turn the cube back to how you started, having green in front again and white on top. Now rotate the cube backwards 90 degrees, resulting in green on top and yellow facing the camera. Now you can scan in the last yellow side.

If you've done the steps above correctly, you should have a solution from Qbr.

Keybindings

• SPACE for saving the current state

• ESC quit

• c toggle calibrate mode

• l switch interface language

Parameters

You can use -n or --normalize to also output the solution in a "human-readable" format.

For example:

• R will be: Turn the right side a quarter turn away from you.
• F2 will be: Turn the front face 180 degrees.

Example runs

$ ./qbr.py
Starting position:
front: green
top: white

Moves: 20
Solution: U2 R D2 L2 F2 L U2 L F' U L U R2 B2 U' F2 D2 R2 D2 R2

$ ./qbr.py -n
Starting position:
front: green
top: white

Moves: 20
Solution: B2 U2 F' R U D' L' B' U L F U F2 R2 F2 D' F2 D R2 D2
1. Turn the back side 180 degrees.
2. Turn the top layer 180 degrees.
3. Turn the front side a quarter turn to the left.
4. Turn the right side a quarter turn away from you.
5. Turn the top layer a quarter turn to the left.
6. Turn the bottom layer a quarter turn to the left.
7. Turn the left side a quarter turn away from you.
8. Turn the back side a quarter turn to the right.
9. Turn the top layer a quarter turn to the left.
10. Turn the left side a quarter turn towards you.
11. Turn the front side a quarter turn to the right.
12. Turn the top layer a quarter turn to the left.
13. Turn the front side 180 degrees.
14. Turn the right side 180 degrees.
15. Turn the front side 180 degrees.
16. Turn the bottom layer a quarter turn to the left.
17. Turn the front side 180 degrees.
18. Turn the bottom layer a quarter turn to the right.
19. Turn the right side 180 degrees.
20. Turn the bottom layer 180 degrees.

Inspirational sources

Special thanks to HaginCodes for the main inspiration on how to improve my color detection.

https://github.com/HaginCodes/3x3x3-Rubiks-Cube-Solver

http://programmablebrick.blogspot.com/2017/02/rubiks-cube-tracker-using-opencv.html

https://gist.github.com/flyboy74/2cc3097f784c8c236a1a85278f08cddd

https://github.com/dwalton76/rubiks-color-resolver

License

Qbr is licensed under the MIT License.