From 77097029db4599f5b4f2f9a8c788f6e7d717b4cb Mon Sep 17 00:00:00 2001
From: alemuntoni <muntoni.alessandro@gmail.com>
Date: Mon, 25 Oct 2021 10:41:58 +0200
Subject: [PATCH] add export eigen edge matrix from CMesh

---
 .../utilities/eigen_mesh_conversions.cpp      | 26 +++++++++++++++++++
 src/common/utilities/eigen_mesh_conversions.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/src/common/utilities/eigen_mesh_conversions.cpp b/src/common/utilities/eigen_mesh_conversions.cpp
index d20f934ed..3b894d8fc 100644
--- a/src/common/utilities/eigen_mesh_conversions.cpp
+++ b/src/common/utilities/eigen_mesh_conversions.cpp
@@ -555,6 +555,32 @@ Eigen::MatrixX3i meshlab::faceMatrix(const CMeshO& mesh)
 	return faces;
 }
 
+/**
+ * @brief Get a #E*2 Eigen matrix of integers containing the vertex indices of
+ * the edges of a CMeshO.
+ * The edges in the mesh must be compact (no deleted edges).
+ * If the mesh is not compact, a vcg::MissingCompactnessException will be thrown.
+ *
+ * @param mesh: input mesh
+ * @return #E*2 matrix of integers (vertex indices composing the edges)
+ */
+Eigen::MatrixX2i meshlab::edgeMatrix(const CMeshO& mesh)
+{
+	vcg::tri::RequireEdgeCompactness(mesh);
+
+	// create eigen matrix of edges
+	Eigen::MatrixXi edges(mesh.EN(), 2);
+
+	// copy faces
+	for (int i = 0; i < mesh.EN(); i++) {
+		for (int j = 0; j < 2; j++) {
+			edges(i, j) = (int) vcg::tri::Index(mesh, mesh.edge[i].V(j));
+		}
+	}
+
+	return edges;
+}
+
 /**
  * @brief Get a #F list of Eigen vectors of integers containing the vertex indices of
  * the polygonal mesh contained in the CMeshO mesh.
diff --git a/src/common/utilities/eigen_mesh_conversions.h b/src/common/utilities/eigen_mesh_conversions.h
index 08f4ee89c..7bf55913e 100644
--- a/src/common/utilities/eigen_mesh_conversions.h
+++ b/src/common/utilities/eigen_mesh_conversions.h
@@ -82,6 +82,7 @@ void addFaceVectorAttribute(
 // From CMeshO to Eigen
 EigenMatrixX3m            vertexMatrix(const CMeshO& mesh);
 Eigen::MatrixX3i          faceMatrix(const CMeshO& mesh);
+Eigen::MatrixX2i          edgeMatrix(const CMeshO& mesh);
 std::list<EigenVectorXui> polygonalFaceList(const CMeshO& mesh);
 EigenMatrixX3m            vertexNormalMatrix(const CMeshO& mesh);
 EigenMatrixX3m            faceNormalMatrix(const CMeshO& mesh);