Loading...
Logo
Processing Forum
Programming Questions
david-wilson
David Wil..

Flickering gap caused by Thread/Draw sync?

in Programming Questions  •  2 years ago  
Hi all,

The code below is an example of some code I'm using for a game. The problem is the 1px(?) line appearing intermittently after the last Thing in the array. I suspect that this is because  draw() is rendering what's happening irrelevant of whether or not the ThingMover (on a separate Thread) has finished updating or not, which was really the point of using the thread in the first place. 

Does anyone have any ideas on how I might get rid of the flickering gap? I've had a go at using a boolean to make sure only either draw or the ThingMover's run() method is being accessed at any one time with little success, so any help would be much appreciated.

Thanks very much

Dave

Processing user on Google Plus? http://gplus.to/calx

int numThings = 15;
int thingSize = 64;
String here = "<< here";

ThingMover thingMover;

void setup() 
{  
  size(800, 480); 

  thingMover = new ThingMover();
  thingMover.start();
  noStroke();
  noSmooth();
  frameRate(6000);
}

void draw() 
{
  background(0, 255, 0);
  thingMover.displayThings();
}

class Thing
{

  float x, y, w, h, speed;
  int id;

  Thing(float x, float y, float w, float h, float speed, int id)
  {
    this.x = x;    
    this.y = y;    
    this.w = w;
    this.h = h;
    this.speed = speed;
    this.id = id;
  }

  void move()
  {
    x+=speed;
    if (x <= -thingSize)
    {
      x = (numThings-1)*thingSize;
    }
  }

  void display()

  {  
    fill(255);
    rect(x, y, w, h);
    if (id == 0) 
    {
      fill(0);
      text(here, x, y+100);
    }
  }
}

class ThingMover extends Thread
{

  Thing[] things = new Thing[numThings];
  boolean running;

  ThingMover()
  {
    for (int i = 0; i < things.length; i++) 
    {
      things[i] = new Thing(i*thingSize, (height/2)+(i*-2), 64, 400, -1, i);
    }

    running = true;
  }

  void run() 
  { 
    while (running) 
    {
      try 
      {
        sleep(5);
      } 
      catch (Exception e) 
      {
        //one day I really will fill this out.
      }
      updateThings();
    }
  }

  void updateThings()
  {
    for (int i = 0; i < things.length; i++) 
    {
      things[i].move();
    }
  }

  void displayThings()
  {
    for (int i = 0; i < things.length; i++) 
    {
      things[i].display();
    }
  }
}

Replies(2)

quarks
quarks

Re: Flickering gap caused by Thread/Draw sync?

2 years ago
You are right in that you need a boolean (in threading this is called a semaphore) to control access  to the data. The line is caused by attempting to draw and update the things at the same time.

I have added a semaphore to your code and tested it. No flickering line now.

Copy code
  1. int numThings = 15;
  2. int thingSize = 64;
  3. String here = "<< here";
  4. ThingMover thingMover;
  5. boolean locked = false;

  7. void setup() { 
  8.   size(800, 480);
  9.   thingMover = new ThingMover();
  10.   thingMover.start();
  11.   noStroke();
  12.   noSmooth();
  13.   frameRate(6000);
  14. }

  16. void draw() {
  17.   background(0, 255, 0);
  18.   while (locked);
  19.   locked = true;
  20.   thingMover.displayThings();
  21.   locked = false;
  22. }

  24. class Thing {
  25.   float x, y, w, h, speed;
  26.   int id;
  27.   Thing(float x, float y, float w, float h, float speed, int id) {
  28.     this.x = x;   
  29.     this.y = y;   
  30.     this.w = w;
  31.     this.h = h;
  32.     this.speed = speed;
  33.     this.id = id;
  34.   }

  36.   void move() {
  37.     x+=speed;
  38.     if (x <= -thingSize) {
  39.       x = (numThings-1)*thingSize;
  40.     }
  41.   }

  43.   void display() { 
  44.     fill(255);
  45.     rect(x, y, w, h);
  46.     if (id == 0) {
  47.       fill(0);
  48.       text(here, x, y+100);
  49.     }
  50.   }
  51. }

  53. class ThingMover extends Thread {
  54.   Thing[] things = new Thing[numThings];
  55.   boolean running;
  56.   ThingMover() {
  57.     for (int i = 0; i < things.length; i++) {
  58.       things[i] = new Thing(i*thingSize, (height/2)+(i*-2), 64, 400, -1, i);
  59.     }
  60.     running = true;
  61.   }

  63.   void run() {
  64.     while (running) {
  65.       try {
  66.         sleep(5);
  67.       }
  68.       catch (Exception e) {
  69.         //one day I really will fill this out.
  70.       }
  71.       if (!locked) {
  72.         locked = true;
  73.         updateThings();
  74.       }
  75.       locked = false;
  76.     }
  77.   }

  79.   void updateThings() {
  80.     for (int i = 0; i < things.length; i++) {
  81.       things[i].move();
  82.     }
  83.   }

  85.   void displayThings() {
  86.     for (int i = 0; i < things.length; i++) {
  87.       things[i].display();
  88.     }
  89.   }
  90. }

David Wilson
David Wil..

Re: Re: Flickering gap caused by Thread/Draw sync?

2 years ago
Thankyou! The point of having updateThings() and displayThings() on separate threads was to get the smoothest possible movement, but here they are dependent on each other again, and the movement is back to stuttering as the move function waits for draw to complete.  I fixed this by switching the boolean the other way around, where displayThings() only runs if  updateThings()  has finished.

Thanks

Dave

Processing user on Google Plus? http://gplus.to/calx

int numThings = 15;
int thingSize = 64;
String here = "<< here";
ThingMover thingMover;
boolean locked = false;

void setup() { 
  size(800, 480);
  thingMover = new ThingMover();
  thingMover.start();
  noStroke();
  noSmooth();
  frameRate(6000);
}

void draw() {
  background(0, 255, 0);
  if (!locked) {
    locked = true;
    thingMover.displayThings();
  }
  locked = false;
}

class Thing {
  float x, y, w, h, speed;
  int id;
  Thing(float x, float y, float w, float h, float speed, int id) {
    this.x = x;   
    this.y = y;   
    this.w = w;
    this.h = h;
    this.speed = speed;
    this.id = id;
  }

  void move() {
    x+=speed;
    if (x <= -thingSize) {
      x = (numThings-1)*thingSize;
    }
  }

  void display() { 
    fill(255);
    rect(x, y, w, h);
    if (id == 0) {
      fill(0);
      text(here, x, y+100);
    }
  }
}

class ThingMover extends Thread {
  Thing[] things = new Thing[numThings];
  boolean running;
  ThingMover() {
    for (int i = 0; i < things.length; i++) {
      things[i] = new Thing(i*thingSize, (height/2)+(i*-2), 64, 400, -1, i);
    }
    running = true;
  }

  void run() {
    while (running) {
      try {
        sleep(5);
      }
      catch (Exception e) {
        //one day I really will fill this out.
      }
      while (locked);
      locked = true;
      updateThings();
      locked = false;
    }
  }

  void updateThings() {
    for (int i = 0; i < things.length; i++) {
      things[i].move();
    }
  }

  void displayThings() {
    for (int i = 0; i < things.length; i++) {
      things[i].display();
    }
  }
}

Top Reply

Statistics

  • 2 Replies
  • 1338  Views
  • 0 Followers

Tags

No tags available for this topic.

Actions

Related Posts