[marker management]
every frame, detector returns a list of active markers.
compare each against markers from last frame.
comparison:
	for each detectedMarker {
		closestMarker = null;
		for each activeMarker {
			if (detectedMarker.codeId == activeMarker.codeId) {
				if detectedMarker.position is closer than closestMarker.position
				(or closestMarker == null) {
					store activeMarker as closest marker.
				}
			}
		}
		if (closestMarker) {
			if within threshold, it's the same marker, so update it.
			add to updatedMarkers list (local, not member).
			--MARKER_UPDATED--
			continue;
		}
		
		(else)
		detectedMarker is new marker.
		--MARKER_ADDED--
	}
	
	for each (activeMarker) {
		if activeMarker is not in updatedMarkers list, remove it.
		--MARKER_REMOVED--
	}

member vars:
	activeMarkers
	position threshold
	transformation threshold(s)




posted here:
http://www.mikkoh.com/blog/?p=182


SOC: note also that i can test without a camera;
load a bitmap image from file instead of from a camera stream.
in mikko's example, dump the loaded image as a BitmapData into the 'capture' var.
FLAR__MarkerDetector.detectMarkerLite accepts a FLARRgbRaster_BitmapData, which just wraps a BitmapData instance. 



i haven't tried this yet, but looking through FLARMultiMarkerDetector, it looks like the way to use it is basically:

create multiple .patt files, and embed them in your Main.as file.
note that they must all be the same size! (we're using 16x16)

instantiate a FLARMultiMarkerDetector (instead of a FLARSingleMarkerDetector).

create an Array of N FLARTransMatResult instances (instead of just one).

call FLARMultiMarkerDetector.detectMarkerLite(); this will return the amount of detected markers.  let's call this amount N.

loop through that Array, and call FLARMultiMarkerDetector.getTransmationMatrix() for each FLARTransMatResult.

call setTransformationMatrix on all of your FLARBaseNodes.

the one thing i'm not yet sure about is how to tell which detected marker is which.  ah wait.  looks like each detected marker has a property called 'codeId', and you can find the codeId of each of FLARMultiMarkerDetector's results with FLARMultiMarkerDetector.getARCodeIndex().  however, it's referencing a variable that doesn't exist.  in FLARMultiMarkerDetector, change this line:
return this._result_holder.result_array[i_index].arcode_id;

to this:
return this._result_holder.result_array[i_index].codeId;

also, note that FLARMultiMarkerDetector has a bunch of trace statements in it that will likely slow down the application; it's best to comment these out.


phew.  sorry about the brain dump.  here's a code example.  it's *very* untested and incomplete, and only shows changes from mikko's code.


[Embed(source="../lib/mikko01.pat", mimeType="application/octet-stream")]
private var MarkerPattern01:Class;

[Embed(source="../lib/mikko02.pat", mimeType="application/octet-stream")]
private var MarkerPattern02:Class;

[Embed(source="../lib/mikko03.pat", mimeType="application/octet-stream")]
private var MarkerPattern03:Class;


public function Main () :void {
	// init patterns and multi-marker detector
	var patternClasses:Array = {MarkerPattern01, MarkerPattern02, MarkerPattern03};
	markerPatterns = new Array(patternClasses);
	for (var i:int=0; i<patternClasses.length; i++) {
		markerPatterns[i] = new FlarCode(16, 16);
		markerPattern[i].loadARPatt(new (patternClasses[i] as Class)());
	}
	detector = new FLARMultiMarkerDetector(cameraParameters, markerPatterns, 80, markerPatterns.length);
	
	// init transformation matrices, used to report the results of marker(s) detection
	transMats = new Array(markerPatterns.length);
	for (var i:int=0; i<markerPatterns.length; i++) {
		transMats[i] = new FLARTransMatResult();
	}
	
	// init base nodes
	baseNodes = new Array(markerPatterns.length);
	for (var i:int=0; i<markerPatterns.length; i++) {
		baseNodes[i] = new FLARBaseNode();
	}
}	

private function mainEnter (e:Event) :void {
	capture.draw(vid);
	
	var numDetectedMarkers:int = detector.detectMarkerLite(raster, 100);
	var markerId:int;
	for (var i:int=0; i<numDetectedMarkers; i++) {
		// ignore detected markers with low confidence
		if (detector.getConfidence(i) < 0.5) { return; }
		
		// figure out which marker we're looking at
		markerId = detector.getARCodeIndex(i);
		
		// set the transformation matrix accordingly
		detector.getTransmationMatrix(i, transMats[markerId]);
	}
	
	// apply transformation matrices to base nodes
	for (i=0; i<baseNodes.length; i++) { 
		baseNodes[i].setTransformMatrix(transMats[i]);
	}
	
	//Render the papervision scene
	renderer.render();
}