function loop() {
			if(gl.destroyed) //to stop rendering once it is destroyed
				return;

			context._requestFrame_id = post(loop); //do it first, in case it crashes

			var now = getTime();
			var dt = (now - time) * 0.001;
			if(context.mouse)
				context.mouse.last_buttons = last_mouse_buttons;
			last_mouse_buttons = context.mouse.buttons;
			if (context.onupdate) 
				context.onupdate(dt);
			LEvent.trigger( context, "update", dt);
			if (context.ondraw)
			{
				//make sure the ondraw is called using this gl context (in case there is more than one)
				var old_gl = global.gl;
				global.gl = context;
				//call ondraw
				context.ondraw();
				LEvent.trigger(context,"draw");
				//restore old context
				global.gl = old_gl;
			}
			time = now;
		}
Launch animation loop (calls gl.onupdate and gl.ondraw every frame)
example: gl.ondraw = function(){ ... }   or  gl.onupdate = function(dt) { ... }
@method animate