IOS "append" function

[EvanZhang0710]

I understand that the IOS rtabmap uses loop detection to realize the "append" function. I want to play around with the "append" function and integrate new features into it. However, I am kind of confused about which file and which code chunk specifically implements this. Any suggestions?

Thanks!

[matlabbe]

The "append" mode is implicitly handled with the loop closure detector and by setting Rtabmap/StartNewMapOnLoopClosure parameter to true (set here for mobile apps) to avoid adding new data to database before a loop closure is accepted with a previous map inside it. For each new image, we update the Bayes filter for loop closure detection, and in case of Append mode, we aggressively try to close the loop on the highest hypothesis (on the mobile app _aggressiveLoopThr is zero):

rtabmap/corelib/src/Rtabmap.cpp

Lines 2123 to 2125 in 1ab0133

	// use the best hypothesis directly.
	UDEBUG("Using %s=%f", Parameters::kRGBDAggressiveLoopThr().c_str(), _aggressiveLoopThr);
	loopThr = _aggressiveLoopThr;

Computation of the loop closure constraint happens here:

rtabmap/corelib/src/Rtabmap.cpp

Lines 3007 to 3025 in 1ab0133

	//=============================================================
	// Global loop closure detection
	// (updated: place this after retrieval to be sure that neighbors of the loop closure are in RAM)
	//=============================================================
	if(_loopClosureHypothesis.first>0)
	{
	if(loopIdSuppressedByProximity==0)
	{
	//Compute transform if metric data are present
	Transform transform;
	RegistrationInfo info;
	info.covariance = cv::Mat::eye(6,6,CV_64FC1);
	if(_rgbdSlamMode)
	{
	transform = _memory->computeTransform(
	_loopClosureHypothesis.first,
	signature->id(),
	_loopClosureIdentityGuess?Transform::getIdentity():Transform(),
	&info);

If a constraint is found, rtabmap will start to appends new data to the database, otherwise the new image is discarded:

rtabmap/corelib/src/Rtabmap.cpp

Lines 4243 to 4253 in 1ab0133

	if(_startNewMapOnLoopClosure &&
	_memory->isIncremental() && // only in mapping mode
	graph::filterLinks(signature->getLinks(), Link::kSelfRefLink).size() == 0 && // alone in the current map
	(landmarksDetected.empty() || rejectedLandmark) && // if we re not seeing a landmark from a previous map
	_memory->getWorkingMem().size()>=2) // The working memory should not be empty (beside virtual signature)
	{
	UWARN("Ignoring location %d because a global loop closure is required before starting a new map!",
	signature->id());
	signaturesRemoved.push_back(signature->id());
	_memory->deleteLocation(signature->id());
	}