[Java-player-users] Fiducial problems

[Shane H. <sr...@ny...>]

Hi everyone -

I'm trying to get fiducials to work with stage 1.3.5, player 1.6.5, and 
the latest javaclient.  My worldfile seems to be ok, since on the stage 
GUI I can see the little numbers that come up when a fiducial comes in 
range of the laser finder, but just for reference here's a robot from 
the worldfile:

shane_pioneer( color "blue" name "robot1"
               port 6666 pose [3.753 7.901 -2.915 ]
          fiducial_id 88)


Here is the function that updates the fiducials:

    ///////////////////////////////////////////////   
    public void updateFid() {

        FiducialInterface fi = getFidInterface();
       
        int numFids = fi.getFiducialCount();
        boolean isReady = fi.isIDReady();
       
        pl("numFids is " + numFids + " isReady " + isReady);
       
        if (numFids > 0 && isReady == true) {
            PlayerFiducialItem[] fs = fi.getFiducials();
            for (PlayerFiducialItem fItem : fs) {
                if (fItem == null) {
                    pl("Null fi!");
                    break;
                } else {
                    pl (getName() + " fItem.id " + fItem.getID());
                }
            }
        }
    }

Here is an excerpt of what it outputs:

----
[Fiducial] : Error when reading payload: java.lang.NullPointerException
[Fiducial] : Error when reading payload: java.lang.NullPointerException
numFids is 2 isReady false
numFids is 2 isReady false
numFids is 2 isReady false
[Fiducial] : Error when reading payload: java.lang.NullPointerException
numFids is 2 isReady false
[Fiducial] : Error when reading payload: java.lang.NullPointerException
numFids is 2 isReady false
numFids is 2 isReady false
numFids is 2 isReady false
[Fiducial] : Error when reading payload: java.lang.NullPointerException
----

I'm at a loss for what's going on.  The numFids count is right - there 
are indeed two fiducial objects in range.  If I move the robot around 
and get it out of range - so that numFids is 0 - all these 
NullPointerExceptions go away.  (Note that these NullPointerException 
messages are coming in on stderr - it's javaclient generating them, not 
my code.)

It's weird that javaclient/player knows there are 2 fids, but none of 
them ever get returned, and isReady is always false.  (Note that if you 
take out the isReady == true test it prints out "Null fi!" every time - 
there's no fiducial info there.)

Does anyone have any clue about what's going on?  Advice of what I can 
try next?  Working code samples that show how to work with the fiducial 
interface?

Thanks a lot.

Shane

PS: In the interest of science, or karma, I'll donate all of my code to 
the javaclient project when I'm done with it, so newbies can have some 
working examples to look at.  It's been really frustrating that there's 
so little actual working code available that does anything, not just for 
javaclient but for player/stage in general.  I don't get it; this is 
open source, is it not?  We're all about sharing here?