Elastic camera code

elastic-camera.ts

var cameraVel = new ex.Vector(0, 0);
engine.on('update', function(){
  
  // Calculate the center of mass between the players on screen
  // this is sort of a naive way to do co-op camera but works for now
	var playerAvg = players.reduce(function(last, current, i){
		return new ex.Vector(last.x + current.x, last.y + current.y);
	}, ex.Vector.Zero.clone()).scale(1/players.length);
	
	// Grab the current focus of the camper
	var focus = engine.currentScene.camera.getFocus().toVector();
	
	// Grab the "destination" position, in the spring equation the displacement location
	var position = new ex.Vector(playerAvg.x, playerAvg.y);
	
	// Calculate the strech vector, using the spring equation
	// F = kX
	// https://en.wikipedia.org/wiki/Hooke's_law
	// Apply to the current camera velocity
	var stretch = position.minus(focus).scale(Config.CameraElasticity);
	cameraVel = cameraVel.plus(stretch);
	
	// Calculate the friction (-1 to apply a force in the opposition of motion)
	// Apply to the current camera velocity
	var friction = cameraVel.scale(-1).scale(Config.CameraFriction);
	cameraVel = cameraVel.plus(friction);
	
	// Update position by velocity deltas
	focus = focus.plus(cameraVel);
	
	// Set new position on camera
	engine.currentScene.camera.setFocus(focus.x, focus.y);
	
});