tandon created this revision. tandon added reviewers: nienhueser, rahn. tandon added a subscriber: nienhueser. tandon set the repository for this revision to R34 Marble. tandon added a project: Marble.
REVISION SUMMARY The older buildings merger was using DBSCAN clustering algorithm to identify building clusters and was then merging all the buildings in a particular cluster into a single building. However, this approach was resulting in formation of irregular buildings/polygons. This new buildings merger, instead of finding cluster of buildings, is finding buildings which share a common boundary and all the buildings which share a common boundary are then merged into a single building. The algorithm was suggested to me by @nienhueser > The idea is to construct a graph where each node is a building and two nodes are connected by an edge in case they share a common point. This could be done by using a QHash<GeoDataCoordinates, QSet<GeoDataPlacemark*> > which would be filled by iterating over all outer boundaries of the building polygons. Afterwards this data structure would have to be converted to a graph. An adjacency matrix might be an easy way to represent/construct it. In the last step the clustering could be performed in that graph: all nodes connected by edges are a cluster. After forming the graph, the program is finding strongly connected components to identify the buildings which share a common boundary. Each graph component is then merged into a single building. This is done via edge-contraction, i.e. the program takes two adjacent nodes(buildings) of a graph and merges them into a single node. It keeps on doing this for a component till a single node/building is reached. However, some problems are still persisting- In-spite of having common boundaries, QPolygonF::united() is not merging two adjacent buildings correctly. In order to circumvent this problem, I used clipper libraries union method. This corrected the above problem, but lead to disappearance of many building blocks. Original F832602: sample.png <https://phabricator.kde.org/F832602> Merged using QPolygonF::united() Buildings not getting merged properly F832609: qpol.png <https://phabricator.kde.org/F832609> Merged using clipper library union method Buildings getting merged but some buildings disappear F832610: clipp.png <https://phabricator.kde.org/F832610> REPOSITORY R34 Marble REVISION DETAIL https://phabricator.kde.org/D3747 AFFECTED FILES tools/vectorosm-tilecreator/BuildingBlock.cpp tools/vectorosm-tilecreator/BuildingBlock.h tools/vectorosm-tilecreator/BuildingMerger.cpp tools/vectorosm-tilecreator/BuildingMerger.h tools/vectorosm-tilecreator/CMakeLists.txt tools/vectorosm-tilecreator/vectorosm-tilecreator.cpp EMAIL PREFERENCES https://phabricator.kde.org/settings/panel/emailpreferences/ To: tandon, nienhueser, rahn Cc: nienhueser, mnafees, shentey, chaz6, dkolozsvari, cmihalache, rahn, marble-devel
