NaviTrack Tutorial:Integrating:Passing coordinates data

What you need to do

1. Create NaviTrack module to provide a node that can be accessed by you application.
2. Modify your application to push and pull NaviTrack events cyclically with certain interval.
3. Create NaviTrack configuration XML file to build tree structure of data flow.

Sending side

Modify MyTutorialModule

To send data through NaviTrack, it is necessary to generate a new event, which contains the data. The following code is implemented into MyTutorialModule to be called from your application.

void MyTutorialModule::setTracker(std::vector<float> pos,std::vector<float> quat)
{
  if (pos.size() != 3 || quat.size() != 4) {
    std::cout << "MyTutorialModule::setTracker(): illegal vector size." << std::endl;
    return;
  }

  if(source!=NULL)
    {
      ot::Event *event = new ot::Event();
      event->setAttribute("position",pos);
      event->setAttribute("orientation",quat);
      event->timeStamp();
      source->updateObservers( *event );
    }
}

pushpos.cxx

The core part for sending coordinate data is as follows:

 MyTutorialModule* mtm = (MyTutorialModule*) context.getModule("MyTutorialConfig");
 
 while (stopflag == 0) {
   
   // set coordinate data (pos, quat) here
   
   ....
   
   if (mtm) {
     mtm->setTracker(pos, quat);   // call NaviTrack module member function to set data
   }
   
   stopflag = context.loopOnce();  // push and pull evets for NaviTrack
   usleep(rate);
 }

Receiving side

Modify MyTutorialSink and MyTutorialModule

An event to pull coordinate data is handled in onEventGenerated() function in MyTutorialSink. There are two steps to pass the coordinate data to your application: STEP 1) onEventGenerated() stores the data into member variables in MyTutorialSinke; STEP 2) your application fetch the data from MyTutorialSink through MyTutorialModule.

Bellows are examples to implement STEP 1 and STEP 2.

MyTutorialSink.h: Add member variables to hold the coordinate data:

 private:
   std::vector<float> position;
   std::vector<float> orientation;

MyTutorialSink.cxx:

 void MyTutorialSink::onEventGenerated( Event& event, Node& generator)
 {
   if (event.hasAttribute("position"))
     for(int i = 0; i < 3; i ++)
       position[i]=event.getPosition()[i];
   else
     {
       position[0]=0.0;
       position[1]=0.0;
       position[2]=0.0;
     }
 
   if (event.hasAttribute("orientation"))
     {
       for  (int i = 0; i < 4; i ++) {
         orientation[i]= event.getOrientation()[i];
       }
       std::cout << "orientation !!!" << std::endl;
     }
   else
     {
       orientation[0]=0.0;
       orientation[1]=0.0;
       orientation[2]=0.0;
       orientation[3]=0.0;
     }
 }

MyTutorialModule.cxx (and .h): add the follwing function:

 void MyTutorialModule::getTracker(std::vector<float>& pos,std::vector<float>& quat)
 {
   //std::cout << "MyTutorialModule::getTracker() is called." << std::endl;
 
   if(sink!=NULL)
     {
       sink->getTracker(pos, quat);
     }
 }

pullpos.cxx

The core part for receiving coordinate is as follows:

 MyTutorialModule* mtm = (MyTutorialModule*) context.getModule("MyTutorialConfig");
 int i = 0;
 
 while (stopflag == 0) {
   
   stopflag = context.loopOnce();   // push and pull events for NaviTrack
   
   if (mtm) {
     Image img;
     int w, h;
     
     mtm->getImage(img, w, h);       // get data from NaviTrack module
     
     if (img.size() != 0) {
       // Process received image here.
       ...
       
     }
   }
   usleep(rate);
 }

Testing

Let's try to send position data from pushpos to pullpos program through network.

Configure NaviTrack XML files

tutorial_source.xml (for pushpos)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE OpenTracker SYSTEM "../share/navitrack.dtd">
<OpenTracker> 

  <configuration>
    <MyTutorialConfig name="MyModule"/>
    <NetworkSourceConfig name="Network"/>
  </configuration> 

  <NetworkSink mode="unicast" number="1"  port="12345">
    <MyTutorialSource/>
  </NetworkSink>

</OpenTracker>

tutorial_sink.xml (for pullpos)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE OpenTracker SYSTEM "../share/navitrack.dtd">
<OpenTracker>

  <configuration>
    <MyTutorialConfig name="MyModule"/>
    <NetworkConfig name="Network"/>
  </configuration> 

  <MyTutorialSink>
    <NetworkSource mode="unicast" number="1"  address="b2_d4_8" port="12345"/>
  </MyTutorialSink> 

</OpenTracker>

Run the programs

Open two terminals and go to the directory where the programs exists.

Terminal 1 (pushpos: sending side)

$ ./pushpos tutorial_source.xml

Terminal 2 (pullpos: receiving side)

$ ./pullpos tutorial_sink.xml

Back to Integrating into your application.