From 810ddaee0387b976e9a861e90c7dfe2ce06f8a95 Mon Sep 17 00:00:00 2001
From: papush! <contact@ccolin.fr>
Date: Wed, 5 Jan 2022 15:54:46 +0100
Subject: [PATCH] add a method to find connected components

---
 src/util.cpp | 44 ++++++++++++++++++++++++++++++++++++++++++++
 src/util.h   |  4 ++++
 2 files changed, 48 insertions(+)

diff --git a/src/util.cpp b/src/util.cpp
index 1600f9f..5757a99 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -1,5 +1,8 @@
 #include "util.h"
 
+#include <stack>
+#include <OpenMesh/Core/Utils/PropertyManager.hh>
+
 
 QDebug operator<<(QDebug dbg, const Point &p) {
 	return dbg << p[0] << p[1] << p[2];
@@ -9,3 +12,44 @@ QDebug operator<<(QDebug dbg, const Point &p) {
 qreal cotan(const qreal x) {
 	return 1. / qTan(x);
 }
+
+
+static void traverse_connected(MyMesh &mesh, std::vector<VertexHandle> &out,
+							   VertexHandle start) {
+	auto prop =
+		OpenMesh::makeTemporaryProperty<MyMesh::VertexHandle, bool>(mesh);
+	for (VertexHandle vh : mesh.vertices()) {
+		prop[vh] = false;
+	}
+	std::stack<VertexHandle> stack;
+	stack.push(start);
+	prop[start] = true;
+	while (!stack.empty()) {
+		VertexHandle v = stack.top();
+		stack.pop();
+		out.emplace_back(v);
+		for (VertexHandle v2 : mesh.vv_range(v)) {
+			if (!prop[v2]) {
+				stack.push(v2);
+				prop[v2] = true;
+			}
+		}
+	}
+}
+
+
+std::vector<std::vector<VertexHandle>> find_connected_components(
+	MyMesh &mesh) {
+	auto prop =
+		OpenMesh::makeTemporaryProperty<MyMesh::VertexHandle, bool>(mesh);
+	for (VertexHandle vh : mesh.vertices()) {
+		prop[vh] = false;
+	}
+	std::vector<std::vector<VertexHandle>> connected_components;
+	for (VertexHandle vh : mesh.vertices()) {
+		if (prop[vh]) continue;
+		connected_components.push_back({});
+		traverse_connected(mesh, connected_components.back(), vh);
+	}
+	return connected_components;
+}
diff --git a/src/util.h b/src/util.h
index 10985a2..8fc01e7 100644
--- a/src/util.h
+++ b/src/util.h
@@ -101,4 +101,8 @@ standard_deviation(const ForwardIt first,
 }
 
 
+std::vector<std::vector<VertexHandle>> find_connected_components(
+	MyMesh &mesh);
+
+
 #endif