diff --git a/lib/torque/renderer/ball.js b/lib/torque/renderer/ball.js
index 2f4404b..4e55750 100644
--- a/lib/torque/renderer/ball.js
+++ b/lib/torque/renderer/ball.js
@@ -21,17 +21,27 @@ function BallRenderer(thecanvas){
 	this.availableWorkers = 10;
 	this.mode = "heat";
 	this.cachedBalls = [];
+	this.initialize();
 }
 BallRenderer.prototype = {
+	initialize: function(){
+		var self = this;
+		this.torqueLayer._map.on("movestart", function(){ 
+			self.transit = true
+		});
+		this.torqueLayer._map.on("moveend", function(){ 
+			self.transit = false
+		});
+	},
 	getBallIndices: function(x, y){
 		var indices = new Int8Array(2*r+1);
-
 		return indices;
 	},
 	addBall: function(x0, y0, st){
 		this.radius = st["marker-width"];
 		this.RW4 = this.radius * this.width *4;
 		if(this.cachedBalls[this.radius]){
+			if(x0 < 0 || y0 < 0 || x0 > this.width || y0 > this.height) return;
 			var startingPoint = this.getRIndexPos(x0, y0) - this.RW4 - this.radius*4;
 			var i = 0, 
 			pointer = startingPoint,