/*
    Written by Alex Young

    Based on:
        http://en.wikipedia.org/wiki/Aurora_borealis
        http://astronomy.swin.edu.au/~pbourke/fractals/peterdejong/
*/

int width = 400, height = 400;
int iterations;
int colour_rate = 10;
int defaultHeight = 20;

color defaultColour;
color colour;

float x, y, x2, y2, lineHeight = 0;
int px, py;
float a, b, c, d;

void setup()
{
    defaultColour = color(100, 100, 140);

    iterations = 10000;
    
    x = 0;
    y = 0;
    x2 = 0;
    y2 = 0;
    lineHeight = 0;

    size(width, height);
    colorMode(RGB, 255);
    stroke(defaultColour);

    // Make a nice gradient    
    for (y = 0; y < height; y++)
    {
        stroke(red(defaultColour) - (y / 3), green(defaultColour) - (y / 3), blue(defaultColour) - (y / 3));
        line(0, y, width, y);
    }
    
    a = random_coord();
    b = random_coord();
    c = random_coord();
    d = random_coord();
}

void loop()
{
    for (int f = 0; f < 14; f++)
    {
        if (mousePressed == true)
	    {
		    setup();
	    }

        if (iterations > 0)
        {
            if (int(lineHeight) < 1)
            {
                lineHeight = defaultHeight;
            }
            
            iterations--;
            
            x2 = cos(a * x) - sin(c * y);
            y2 = sin(b * x) - cos(d * y);
      
            // Convert to screen co-ords
            px = int((x2 + 1) * 70) + 70;
            py = int((y2 + 1) * 70) + 70;
      
            // Get the colour of the pixel
            colour = get(px, py);
                    
            for (int i = 0; i < int(lineHeight); i++)
            {
                set(px, py + i, colour);
                colour = color(red(colour) + (i / 2), green(colour) + (i / 2), blue(colour) + (i / 2));
            }
            
            lineHeight -= 0.1;
            
            x = x2;
            y = y2;
         }
    }
}

float random_coord()
{
    if (random(1) > 0.7)
    {
        return random(3)  * -1;
    }
    else
    {
        return random(3);
    }
}