Add ability to get the original vertex index from the convex hull (#3018)

This makes it possible to know which input verticies were picked to
to define the hull.

With this information it is much easier to map certain features from the
input mesh/point cloud to the output convex hull.

2 files changed, 5 insertions, 0 deletions

diff --git a/src/LinearMath/btConvexHullComputer.cpp b/src/LinearMath/btConvexHullComputer.cpp
index 8bbfdc5f2..fe1981a9a 100644
--- a/src/LinearMath/btConvexHullComputer.cpp
+++ b/src/LinearMath/btConvexHullComputer.cpp
@@ -2673,6 +2673,7 @@ btScalar btConvexHullComputer::compute(const void* coords, bool doubleCoords, in
 	}
 
 	vertices.resize(0);
+	original_vertex_index.resize(0);
 	edges.resize(0);
 	faces.resize(0);
 
@@ -2683,6 +2684,7 @@ btScalar btConvexHullComputer::compute(const void* coords, bool doubleCoords, in
 	{
 		btConvexHullInternal::Vertex* v = oldVertices[copied];
 		vertices.push_back(hull.getCoordinates(v));
+		original_vertex_index.push_back(v->point.index);
 		btConvexHullInternal::Edge* firstEdge = v->edges;
 		if (firstEdge)
 		{
diff --git a/src/LinearMath/btConvexHullComputer.h b/src/LinearMath/btConvexHullComputer.h
index cba684f2d..18b26eea9 100644
--- a/src/LinearMath/btConvexHullComputer.h
+++ b/src/LinearMath/btConvexHullComputer.h
@@ -66,6 +66,9 @@ public:
 	// Vertices of the output hull
 	btAlignedObjectArray<btVector3> vertices;
 
+	// The original vertex index in the input coords array
+	btAlignedObjectArray<int> original_vertex_index;
+
 	// Edges of the output hull
 	btAlignedObjectArray<Edge> edges;