kociemba

This project implements the solution for a Rubik's Cube using C++ and OpenCV. It may be used in certain Rubik's Cube robots in the future. The algorithm used for solving the Rubik's Cube is the Kociemba two-phase algorithm. You can find more details about it on the official website: http://kociemba.org.

Usage

here is a short demonstration video. Once cmake is compiled, you can run the project.

mkdir build && cd build
cmake ..
make
./src/main 1  # The parameter is the camera number, which is 0 by default

After the camera recognizes the color stability, you can press the corresponding button to save the state of the Rubik's Cube, for example, press U to save the color of the upper layer, and press F to save the color of the previous part. When the colors of the six faces have been saved, press Enter to solve the Rubik's Cube.

The cppkociemba folder contains the program for the algorithm, which can be used independently. Here is an example:

#include <iostream>
#include "kociemba.h"

int main() {

    std::string cube = "DRURUFBBDBDFRRLUFDRULLFUURLLDFUDLRFRLBUDLBDLBRFFDBBFUB";

    //kociemba(std::string cube, int maxDepth = 24, int timeOut = 1000, std::filesystem::path cachePath = "./cache)
    std::string solution = kociemba(cube, 24, 1000, "./cache");
    
    //output：R L2 F B U' F' D F' U B2 L' U2 B2 U D' B2 U2 L2 D' R2 D2 
    std::cout << solution << std::endl;

    return 0;
}

After the program is run, it will generate some file storage pruning lookup table (about 7 Mb) in the cache directory, and read the cache file directly to speed up the solution of the Rubik's cube next time.

Cube string notation

The names of the facelet positions of the cube (letters stand for Up, Left, Front, Right, Back, and Down):

             |************|
             |*U1**U2**U3*|
             |************|
             |*U4**U5**U6*|
             |************|
             |*U7**U8**U9*|
             |************|
 ************|************|************|************
 *L1**L2**L3*|*F1**F2**F3*|*R1**R2**R3*|*B1**B2**B3*
 ************|************|************|************
 *L4**L5**L6*|*F4**F5**F6*|*R4**R5**R6*|*B4**B5**B6*
 ************|************|************|************
 *L7**L8**L9*|*F7**F8**F9*|*R7**R8**R9*|*B7**B8**B9*
 ************|************|************|************
             |************|
             |*D1**D2**D3*|
             |************|
             |*D4**D5**D6*|
             |************|
             |*D7**D8**D9*|
             |************|

A cube definition string "UBL..." means that in position U1 we have the U-color, in position U2 we have the B-color, in position U3 we have the L color etc. according to the order U1, U2, U3, U4, U5, U6, U7, U8, U9, R1, R2, R3, R4, R5, R6, R7, R8, R9, F1, F2, F3, F4, F5, F6, F7, F8, F9, D1, D2, D3, D4, D5, D6, D7, D8, D9, L1, L2, L3, L4, L5, L6, L7, L8, L9, B1, B2, B3, B4, B5, B6, B7, B8, B9.

So, for example, a definition of a solved cube would be UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB

Solution string consists of space-separated parts, each of them represents a single move:

• A single letter by itself means to turn that face clockwise 90 degrees.
• A letter followed by an apostrophe means to turn that face counterclockwise 90 degrees.
• A letter with the number 2 after it means to turn that face 180 degrees.

e.g. R U R' U R U2 R' U

Performance

No systematic tests have been done, but solving a common Rubik's cube takes about 10 milliseconds.

Testing

Reference library

Here are some of the libraries used in this project:

• muodov/kociemba - A pure Python and pure C ports of Kociemba's algorithm for solving Rubik's cube
• nicpatel963/CubeSolvingScript - In this script I have implemented a code for detection of cube and solving it.(also GUI based solution)