Use signed int for clustering/grouping

Modify DBSCAN to use the standard ClusterID dimension, which is now
defined as int64. The Groupby filter is similarly instructed to evaluate
int64. This allows clustering algorithms like DBSCAN to use -1 to
indicate noise.

filters/DBSCANFilter.cpp

@@ -45,6 +45,8 @@
 namespace pdal
 {
 
+using namespace Dimension;
+
 static StaticPluginInfo const s_info{
     "filters.dbscan", "DBSCAN Clustering.",
     "http://pdal.io/stages/filters.dbscan.html"};
@@ -71,8 +73,7 @@ void DBSCANFilter::addArgs(ProgramArgs& args)
 
 void DBSCANFilter::addDimensions(PointLayoutPtr layout)
 {
-    m_cluster =
-        layout->registerOrAssignDim("ClusterID", Dimension::Type::Signed64);
+    layout->registerDim(Id::ClusterID);
 }
 
 void DBSCANFilter::prepared(PointTableRef table)
@@ -83,8 +84,8 @@ void DBSCANFilter::prepared(PointTableRef table)
     {
         for (std::string& s : m_dimStringList)
         {
-            Dimension::Id id = layout->findDim(s);
-            if (id == Dimension::Id::Unknown)
+            Id id = layout->findDim(s);
+            if (id == Id::Unknown)
                 throwError("Invalid dimension '" + s +
                            "' specified for "
                            "'dimensions' option.");
@@ -105,22 +106,22 @@ void DBSCANFilter::filter(PointView& view)
     for (PointId idx = 0; idx < view.size(); ++idx)
     {
         neighbors[idx] = kdfi.radius(idx, m_eps);
-        view.setField(m_cluster, idx, -2);
+        view.setField(Id::ClusterID, idx, -2);
     }
 
     // Second pass through point cloud performs DBSCAN clustering.
     int64_t cluster_label = 0;
     for (PointId idx = 0; idx < view.size(); ++idx)
     {
         // Point has already been labeled, so move on to next.
-        if (view.getFieldAs<int64_t>(m_cluster, idx) != -2)
+        if (view.getFieldAs<int64_t>(Id::ClusterID, idx) != -2)
             continue;
 
         // Density of the neighborhood does not meet minimum number of points
         // constraint, label as noise.
         if (neighbors[idx].size() < m_minPoints)
         {
-            view.setField(m_cluster, idx, -1);
+            view.setField(Id::ClusterID, idx, -1);
             continue;
         }
 
@@ -132,7 +133,7 @@ void DBSCANFilter::filter(PointView& view)
         neighbors_visited.insert(idx);
 
         // Unlabeled point encountered; assign cluster label.
-        view.setField(m_cluster, idx, cluster_label);
+        view.setField(Id::ClusterID, idx, cluster_label);
 
         // Consider all neighbors.
         while (!neighbors_next.empty())
@@ -143,15 +144,15 @@ void DBSCANFilter::filter(PointView& view)
             neighbors_visited.insert(p);
 
             // Reassign cluster label to neighbor previously marked as noise.
-            if (view.getFieldAs<int64_t>(m_cluster, p) == -1)
-                view.setField(m_cluster, p, cluster_label);
+            if (view.getFieldAs<int64_t>(Id::ClusterID, p) == -1)
+                view.setField(Id::ClusterID, p, cluster_label);
 
             // Neighbor has already been labeled, so move on to next.
-            if (view.getFieldAs<int64_t>(m_cluster, p) != -2)
+            if (view.getFieldAs<int64_t>(Id::ClusterID, p) != -2)
                 continue;
 
             // Assign cluster label to neighbor.
-            view.setField(m_cluster, p, cluster_label);
+            view.setField(Id::ClusterID, p, cluster_label);
 
             // If density of neighbor's neighborhood is sufficient, add it's
             // neighbors to the set of neighbors to consider if they are not

filters/DBSCANFilter.hpp

@@ -56,7 +56,6 @@ class PDAL_DLL DBSCANFilter : public Filter
 private:
     uint64_t m_minPoints;
     double m_eps;
-    Dimension::Id m_cluster;
     StringList m_dimStringList;
     Dimension::IdList m_dimIdList;
 

filters/GroupByFilter.cpp

@@ -77,7 +77,7 @@ PointViewSet GroupByFilter::run(PointViewPtr inView)
 
     for (PointId idx = 0; idx < inView->size(); idx++)
     {
-        uint64_t val = inView->getFieldAs<uint64_t>(m_dimId, idx);
+        int64_t val = inView->getFieldAs<int64_t>(m_dimId, idx);
         PointViewPtr& outView = m_viewMap[val];
         if (!outView)
             outView = inView->makeNew();

pdal/Dimension.json

@@ -376,7 +376,7 @@
     },
     {
     "name": "ClusterID",
-    "type": "uint64_t",
+    "type": "int64_t",
     "description": "ID assigned to a point by a point-clustering algorithm."
     },
     {