/*
    Multicolored Plasma for the Arduino Micro-Controller and NeoPixel Shield
    Copyright (C) 2019 John Ericksen

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see http://www.gnu.org/licenses/.
*/

#include <Adafruit_NeoPixel.h>

// Parameter 1 = number of pixels in strip
// Parameter 2 = pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_RGB     Pixels are wired for RGB bitstream
//   NEO_GRB     Pixels are wired for GRB bitstream
//   NEO_KHZ400  400 KHz bitstream (e.g. FLORA pixels)
//   NEO_KHZ800  800 KHz bitstream (e.g. High Density LED strip)
const int ROWS = 5;
const int COLS = 8;
const int NUM_LEDS = ROWS * COLS;
const int LED_PIN = 6;
const float phaseIncrement = 0.03;  // Controls the speed of the moving points. Higher == faster. I like 0.08 .
const float colorStretch = 0.3;    // Higher numbers will produce tighter color bands. I like 0.11 .

Adafruit_NeoPixel strip = Adafruit_NeoPixel(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);

// Convenient 2D point structure
struct Point {
  float x;
  float y;
};

void setup() {
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
}

float phase = 0.0;

// This function is called every frame.
void loop() {
  phase += phaseIncrement;
  
  // The two points move along Lissajious curves, see: http://en.wikipedia.org/wiki/Lissajous_curve
  // We want values that fit the LED grid: x values between 0..13, y values between 0..8 .
  // The sin() function returns values in the range of -1.0..1.0, so scale these to our desired ranges.
  // The phase value is multiplied by various constants; I chose these semi-randomly, to produce a nice motion.
  Point p1 = { (sin(phase*1.000)+1.0) * 4.5, (sin(phase*1.310)+1.0) * 4.0 };
  Point p2 = { (sin(phase*1.770)+1.0) * 4.5, (sin(phase*2.865)+1.0) * 4.0 };
  Point p3 = { (sin(phase*0.250)+1.0) * 4.5, (sin(phase*0.750)+1.0) * 4.0 };
  
  byte row, col;
  
  // For each row...
  for( row=0; row<ROWS; row++ ) {
    float row_f = float(row);  // Optimization: Keep a floating point value of the row number, instead of recasting it repeatedly.
    
    // For each column...
    for( col=0; col<COLS; col++ ) {
      float col_f = float(col);  // Optimization.
      
      // Calculate the distance between this LED, and p1.
      Point dist1 = { col_f - p1.x, row_f - p1.y };  // The vector from p1 to this LED.
      float distance1 = sqrt( dist1.x*dist1.x + dist1.y*dist1.y );
      
      // Calculate the distance between this LED, and p2.
      Point dist2 = { col_f - p2.x, row_f - p2.y };  // The vector from p2 to this LED.
      float distance2 = sqrt( dist2.x*dist2.x + dist2.y*dist2.y );
      
      // Calculate the distance between this LED, and p3.
      Point dist3 = { col_f - p3.x, row_f - p3.y };  // The vector from p3 to this LED.
      float distance3 = sqrt( dist3.x*dist3.x + dist3.y*dist3.y );
      
      // Warp the distance with a sin() function. As the distance value increases, the LEDs will get light,dark,light,dark,etc...
      // You can use a cos() for slightly different shading, or experiment with other functions. Go crazy!
      float color_1 = distance1;  // range: 0.0...1.0
      float color_2 = distance2;
      float color_3 = distance3;
      float color_4 = (sin( distance1 * distance2 * colorStretch )) + 2.0 * 0.5;
      
      // Square the color_f value to weight it towards 0. The image will be darker and have higher contrast.
      color_1 *= color_1 * color_4;
      color_2 *= color_2 * color_4;
      color_3 *= color_3 * color_4;
      color_4 *= color_4;
 
      // Scale the color up to 0..7 . Max brightness is 7.
      strip.setPixelColor(col + (COLS * row), strip.Color(color_1, color_2, color_3));
    }
  }
  strip.show();
}