void startAnimation()
{
_nextDeltaTimeZero = true;
if (_isAnimating)
{
return;
}
// approximate frame rate
// assumes device refreshes at 60 fps
int frameInterval = Mathf.FloorToInt(_animationInterval * 60.0f);
CCDebug.Log("cocos2d: animation started with frame interval: {0:0.00}", 60.0f / frameInterval);
_displayLink.registWithTarget(this, mainLoop, OnGUI);
_isAnimating = true;
}