Quote:

You should get a more stable pose when multiple targets are in view

...

Just be careful with the relative placement of your printed targets, multi target stability depends on the physical object matching the tracker's expectations.

So is the tracker refining the pose calculation based on the known offsets of multiple targets?

I think this is a good situation in which to use multi targets. You should get a more stable pose when multiple targets are in view, the transition between targets will be much faster (if the user pans across the plane), and you won't have to do any extra math to bring the targets into a unified coordinate system. Just be careful with the relative placement of your printed targets, multi target stability depends on the physical object matching the tracker's expectations.

You shouldn't need to play with those hints for tracking a single multi target object.

- Kim

Ok, that was what I suspected, but didn't know if lines like:

QCAR::setHint(QCAR::HINT_MAX_SIMULTANEOUS_IMAGE_TARGETS, 2);
QCAR::setHint(QCAR::HINT_IMAGE_TARGET_MULTI_FRAME_ENABLED, 1);

would change anything.

So I guess the best stability would come from drawing lines between ImageTargets like here: http://ar.qualcomm.at/node/2000410
?

Quote:

Rephrasing: Does a MultiTarget only track one of its ImageTarget children at a time, or does it look for multiple, and build a more stable pose matrix off of the maximum number it can discover?

The implementations that I've seen (e.g. MultiTargets.cpp in the sample ) employ one target at a time.

e.g.

...

int numTrackables=state.getNumActiveTrackables();

        // Browse trackables searching for the MultiTarget
        for (int j=0;j<numTrackables;j++)
        {
            trackable = state.getActiveTrackable(j);
            if (trackable->getType() == QCAR::Trackable::MULTI_TARGET) break;
            trackable=NULL;
        }

        // If it was not found exit
        if (trackable==NULL)
        {
            // Clean up and leave
            glDisable(GL_BLEND);
            glDisable(GL_DEPTH_TEST);

            QCAR::Renderer::getInstance().end();
            return;
        }


        QCAR::Matrix44F modelViewMatrix =
            QCAR::Tool::convertPose2GLMatrix(trackable->getPose());
...
 

So the pose is derived from the first MULTI_TARGET trackable that's found.