iPhone是否有帧频限制？

Question

I as a test, setup my opengl game's update() and render() functions in a while loop on a separate NSThread. It runs at exactly 60FPS. How is this possible? It's what I want actually, but why is it doing that? I thought an NSThread would run as fast as it could...? It seems V-synced.

 func setupGL(){
        glThread = NSThread(target: self, selector: "glRun", object: nil);
        glThread.start();
    }


 func glRun(){
        //Start and run Opengl on a separate Thread
        setupLayer();
        setupContext();
        setupRenderBuffer();
        //setupDepthBuffer();
        setupFrameBuffer();
        engine.setupEngine(GLfloat(self.frame.size.width) * GLfloat(scale), screenHeight: GLfloat(self.frame.size.height) * GLfloat(scale));
        //setupDisplayLink();
        print("THREAD STARTED!");
        while(true){
            update()
            render();
            logger.logFrame();
        }
    }

Answer 1

It's because the iOS reduces usage of the hardware to reasonable levels. The truth is you do not need more than 60fps because the screen will not refresh faster, so the frame rate is limited. In this way the battery life is significantly extended.

Your use of NSThread does not matter in this case because the limits are in the OpenGL layer.

You can control frame rate by setting CADisplayLink and it's frameInterval value.

Answer 2

Yes, there is a frame rate limit on iOS. All iOS devices (as of this writing) refresh the screen at most 60 times per second. See, for example, WWDC 2015 Session 233: Advanced Touch Input on iOS , at 4m20s:

Our products refresh the screen at 60 hertz or 60 times per second.

The iOS OpenGL ES implementation knows this, and synchronizes to the window server's screen refresh.