Spherical lens effect for spinning globe

globe.pde

import processing.video.*;

PImage bg;
Movie mov;
final int w=255;

void setup() {
  size(w,w);
  frameRate(30);
  bg = loadImage("earth1024.jpg");
  mov = new Movie(this,"clouds.mov");
  mov.loop();
}

void draw() {
  background(0);
  if (mov.available()) mov.read();
  if (mov.width==1) return;
    
  for (int j=0; j<w; j++) {
    for (int i=0; i<w; i++) {
      float x=-1+2.0*i/w;
      float y=-1+2.0*j/w;
      float m=x*x+y*y;  //0..2
      float t=(3-sqrt(4-5*m))/(m+1);  //t=1...1.642
      int xx=int(map(x*w*t+frameCount,-370,370,-256,256)+512);
      int yy=int(map(y*w*t,-370,370,-256,256)+256);
      
      if (xx<0) xx+=1024;
      if (xx>1024) xx-=1024;
      if (yy<0) yy+=512;
      if (yy>512) yy-=512;
      
      if (m<.8) set(i,j,blendColor(mov.get(xx,yy), bg.get(xx,yy), SCREEN));
    }    
  }
}