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/********************************************************/
/* Erik Kastner. http://metaatem.net
/* Playing with processing - balls falling
/********************************************************/

import processing.opengl.*;
import javax.media.opengl.*;
PGraphicsOpenGL pgl;
GL gl;

ArrayList balls;  // The balls that wll be drawn
int yPos;  // the "bottom" of the screen
int xPos;
int vec;  // the vector of x's change

void setup() {
  size(400,400,OPENGL);
  background(0);
  yPos = height;
  xPos = width;
  vec = 1;
  
  balls = new ArrayList();
}

void draw() {
  background(0); // clear the scene each time
  lights(); // give the balls some shading
  noStroke();

  // this next group is additive blending via flight404
  pgl = (PGraphicsOpenGL) g;
  gl = pgl.gl;
  
  pgl.beginGL();
  gl.glDisable(GL.GL_DEPTH_TEST);
  gl.glEnable(GL.GL_BLEND);
  gl.glBlendFunc(GL.GL_SRC_ALPHA,GL.GL_ONE);
  pgl.endGL();
  
  // add a new ball every 5 frames
  if(frameCount % 5 == 0)
    balls.add(new Ball());
  
  // loop over all the balls and draw them to the screen
  // I had an else in here to do balls.remove(i) but it didn't work, not sure why
  for (int i=0; i<balls.size(); i++) {
    Ball ba = (Ball)balls.get(i);
    // make sure it's in the view
    if (ba.y < yPos+50) {
      pushMatrix();
      translate(ba.x, ba.y, ba.z);
      fill(ba.c);
      sphere(20);
      popMatrix();
    }
  }
  
  // move the floor up 10 lines
  yPos -= 10;
  
  // shimmy the camera left and right
  xPos += vec;
  
  // change directions - gives the camera a 50 column "sweep" from left to right
  if (xPos >= width+25 || xPos <= width-25) vec *= -1;

  // move the cammera
  camera(xPos-width/2.0, yPos-height/2, (height/2.0) / tan(PI*60.0 / 360.0), xPos-width/2.0, yPos-height/2, 0, 0, 1, 0);
  
  //saveFrame("filename-####.png");
}

class Ball {
  float x;
  float y; 
  float z;
  color c;
  Ball() {
    x = random(width);
    y = random(yPos-height*2, yPos-height*3);
    z = random(-300,300);
    c = color((int)random(255), (int)random(255), (int)random(255), (int)random(100,200));
  }
}