code: public void updateBackground(MotionModel homeToCurrent, T frame) {
  		worldToHome.concat(homeToCurrent, worldToCurrent);
  		worldToCurrent.invert(currentToWorld);
  
  		// find the distorted polygon of the current image in the "home" background reference frame
  		transform.setModel(currentToWorld);
  		transform.compute(0, 0, corners[0]);
  		transform.compute(frame.width-1,0,corners[1]);
  		transform.compute(frame.width-1,frame.height-1,corners[2]);
  		transform.compute(0, frame.height-1, corners[3]);
  
  		// find the bounding box
  		int x0 = Integer.MAX_VALUE;
  		int y0 = Integer.MAX_VALUE;
  		int x1 = -Integer.MAX_VALUE;
  		int y1 = -Integer.MAX_VALUE;
  
  		for (int i = 0; i < 4; i++) {
  			Point2D_F32 p = corners[i];
  			int x = (int)p.x;
  			int y = (int)p.y;
  
  			if( x0 > x ) x0 = x;
  			if( y0 > y ) y0 = y;
  			if( x1 < x ) x1 = x;
  			if( y1 < y ) y1 = y;
  		}
  		x1++;y1++;
  
  		if( x0 < 0 ) x0 = 0;
  		if( x1 > backgroundWidth ) x1 = backgroundWidth;
  		if( y0 < 0 ) y0 = 0;
  		if( y1 > backgroundHeight ) y1 = backgroundHeight;
  
  		updateBackground(x0,y0,x1,y1,frame);
  	}
docs: Updates the background with new image information.
  
  @param homeToCurrent Transform from home image to the current image
  @param frame The current image in the sequence