// simple project with rotating 3D cube using Arduino UNO and Transparent 128x64 OLED Display, 
// Original project by upir, 2022
// youtube channel: https://www.youtube.com/upir_upir
// full tutoral is here: https://youtu.be/kBAcaA7NAlA
// Code amelioration & optimization by: jmdeejay, 2023

// Turbo pressure gauge tutorial: https://youtu.be/JXmw1xOlBdk
// Transparent OLED tutorial: https://youtu.be/hIFDcksXgBk
// Knob + OLED tutorial: https://youtu.be/NPfaLKKsf_Q

// useful links:
// u8g documentation: https://github.com/olikraus/u8glib/wiki/userreference
// Wokwi starting project: https://wokwi.com/arduino/projects/300867986768527882
// Arduino UNO: http://store.arduino.cc/products/arduino-uno-rev3
// Arduino UNO MINI: https://store.arduino.cc/products/uno-mini-le
// Multidimensional arrays: https://www.tutorialspoint.com/arduino/arduino_multi_dimensional_arrays.htm
// 2D Rotation: https://en.wikipedia.org/wiki/Rotation_(mathematics)
// Normal OLED Display: https://www.aliexpress.com/item/4001051535838.html
// Transparent OLED Display: https://a.aliexpress.com/_mKGmhKg
// Big OLED Display: https://www.aliexpress.com/item/1005003091769556.html
// Arduino breadboard prototyping shield: https://www.adafruit.com/product/2077

#include "U8glib.h" // u8g library, note there is a newer version u8g2, please use the older one

const uint8_t upir_logo[] U8G_PROGMEM = { // another simple way how to define pictures for u8g library
B00010101, B11010111,     //  ░░░█░█░███░█░███
B00010101, B01000101,     //  ░░░█░█░█░█░░░█░█
B00010101, B10010110,     //  ░░░█░█░██░░█░██░
B00011001, B00010101      //  ░░░██░░█░░░█░█░█
};

U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_DEV_0 | U8G_I2C_OPT_NO_ACK | U8G_I2C_OPT_FAST); // Fast I2C / TWI

int points[8][2]; // Eight 2D points for the cube, values will be calculated in the code

int orig_points [8][3] = { // Eight 3D points - set values for 3D cube
  {-1,-1, 1},
  {1,-1,1},
  {1,1,1},
  {-1,1,1},
  {-1,-1,-1},
  {1,-1,-1},
  {1,1,-1},
  {-1,1,-1}
};

float rotated_3d_points [8][3]; // eight 3D points - rotated around Y axis
float angle_deg = 60.0;         // rotation around the Y axis
float z_offset = -4.0;          // offset on Z axis
float cube_size = 70.0;         // cube size (multiplier)
float time_frame;               // ever increasing time value

void setup() {
  u8g.setColorIndex(1); // set color to white
}

void loop() {
  time_frame++;                              // increase the time frame value by 1
  cube_size = 50 + sin(time_frame * 0.1)*20; // oscilate cube size between values 50 - 70

  rotateCube();
  calculate3DCube();

  u8g.firstPage();
  do {
    drawCube();
    // draw upir logo 
    u8g.drawBitmapP(112, 0, 2, 4, upir_logo); 
  } while ( u8g.nextPage() );   // u8g library specific, has to be there
}

void rotateCube() {
  // Increase the angle by 1° increments
  if (angle_deg < 90-1) {
    angle_deg = angle_deg + 1;
  } else {
    angle_deg = 0;
  }
}

void calculate3DCube() {
  // Calculate the points
  for (int i=  0; i < 8; i++) {
    // Rotate 3d points around the Y axis (rotating X nad Z positions)
    rotated_3d_points[i][0] = orig_points[i][0] * cos(radians(angle_deg)) - orig_points[i][2] * sin(radians(angle_deg));
    rotated_3d_points[i][1] = orig_points[i][1];
    rotated_3d_points[i][2] = orig_points[i][0] * sin(radians(angle_deg)) + orig_points[i][2] * cos(radians(angle_deg)) + z_offset;  

    // Project 3d points into 2d space with perspective divide -- 2D x = x/z,   2D y = y/z
    points[i][0] = round(64 + rotated_3d_points[i][0] / rotated_3d_points[i][2] * cube_size);
    points[i][1] = round(32 + rotated_3d_points[i][1] / rotated_3d_points[i][2] * cube_size);    
  }
}

void drawCube() {
  // Connect the lines between the individual points.
  u8g.drawLine(points[0][0], points[0][1], points[1][0], points[1][1]); // connect points 0-1
  u8g.drawLine(points[1][0], points[1][1], points[2][0], points[2][1]); // connect points 1-2  
  u8g.drawLine(points[2][0], points[2][1], points[3][0], points[3][1]); // connect points 2-3      
  u8g.drawLine(points[3][0], points[3][1], points[0][0], points[0][1]); // connect points 3-0      

  u8g.drawLine(points[4][0], points[4][1], points[5][0], points[5][1]); // connect points 4-5
  u8g.drawLine(points[5][0], points[5][1], points[6][0], points[6][1]); // connect points 5-6  
  u8g.drawLine(points[6][0], points[6][1], points[7][0], points[7][1]); // connect points 6-7      
  u8g.drawLine(points[7][0], points[7][1], points[4][0], points[4][1]); // connect points 7-4  

  u8g.drawLine(points[0][0], points[0][1], points[4][0], points[4][1]); // connect points 0-4
  u8g.drawLine(points[1][0], points[1][1], points[5][0], points[5][1]); // connect points 1-5  
  u8g.drawLine(points[2][0], points[2][1], points[6][0], points[6][1]); // connect points 2-6      
  u8g.drawLine(points[3][0], points[3][1], points[7][0], points[7][1]); // connect points 3-7  
}