/* built with Studio Sketchpad: 
 *   https://sketchpad.cc
 * 
 * observe the evolution of this sketch: 
 *   https://studio.sketchpad.cc/sp/pad/view/ro.odhT6zZbeFp/rev.807
 * 
 * authors: 
 *   
 *   Roger Allen

 * license (unless otherwise specified): 
 *   creative commons attribution-share alike 3.0 license.
 *   https://creativecommons.org/licenses/by-sa/3.0/ 
 */ 



// Pressing Control-R will render this sketch.
// inspired by
// http://patakk.tumblr.com/post/83247102946

int wr_ptr      = 0;
int FIFO_LEN    = 80;
int WIDTH       = 25;
int WIDTH_INC   = 1.5;
PVector[] xys   = new PVector[FIFO_LEN]; 
PVector[] dxdys = new PVector[FIFO_LEN]; 
float[] widths  = new float[FIFO_LEN];

void setup() {
    for(int i = 0; i < FIFO_LEN; i++) {
        xys[i] = new PVector();
        dxdys[i] = new PVector();
        widths[i] = WIDTH * sin(Math.PI*i/(FIFO_LEN-1)) + WIDTH_INC;
    } 
    size(330, 460); 
    smooth();
    frameRate(30);
} 

void draw3(PVector xy, PVector dxdy, float w)
{
    float x1 = xy.x;
    float y1 = xy.y;
    float x2 = 1.21*dxdy.x*(w-WIDTH_INC) + xy.x;
    float y2 = 1.21*dxdy.y*(w-WIDTH_INC) + xy.y;
    float x3 = 1.21*dxdy.y*(w-WIDTH_INC) + xy.x;
    float y3 = 1.21*dxdy.x*(w-WIDTH_INC) + xy.y;
    strokeWeight(1.5*(w/(WIDTH+WIDTH_INC)));
    fill(230);
    ellipse(x1,y1,w,w);
    fill(210);
    ellipse(x2,y2,w,w);
    fill(180);
    ellipse(x3,y3,w,w);
}

void draw() {  // this is run repeatedly.  
    float ms = millis()/600;
    background(230);
    stroke(0);
    translate(165,225);
    
    xys[wr_ptr].x    = 75*sin(2*ms);
    xys[wr_ptr].y    = 150*cos(1*ms);
    dxdys[wr_ptr].x = sin(3.5*ms);
    dxdys[wr_ptr].y = cos(3.5*ms);
    wr_ptr = (wr_ptr+1)%FIFO_LEN;
    
    for(int i = 0; i < FIFO_LEN; i++) {
        rd_ptr = (wr_ptr+i)%FIFO_LEN;
        draw3(xys[rd_ptr], dxdys[rd_ptr], widths[i]);
    } 
}