How to create TopoDS_Edge from to gp_Pnt in OpenCASCADE

OCCUtils provides a conveniece function for creating a TopoDS_Edge between two points (i.e. a straight line):

#include <occutils/Edge.hxx>

using namespace OCCUtils;

gp_Pnt p1 = /* ... */;
gp_Pnt p2 = /* ... */;

TopoDS_Edge edge = Edge::FromPoints(p1, p2);

In case you want to do it manually (i.e. without OCCUtils), use this snippet

TopoDS_Edge edge = BRepBuilderAPI_MakeEdge(p1, p2).Edge();

but be aware that you also have to handle the case of p1 == p2 i.e.

if (p1.Distance(p2) <= Precision::Confusion()) {
    // Don't try to create an Edge in this case

OCCUtil’s Edge::FromPoints handles this case by returning TopoDS_Edge() i.e. a TopoDS_Edge where edge.IsNull() == true.