From 8655e39fba09d2c0a0ab3d5f1545814d737a8089 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Tue, 6 Feb 2018 20:45:23 +0100
Subject: [PATCH] Add center to a mesh to allow easy translation

---
 Mesh.cpp              | 27 +++++++++++++++++++++++++++
 Mesh.hpp              | 13 +++++++++++++
 common_structures.hpp | 24 ++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/Mesh.cpp b/Mesh.cpp
index 815aad2..7fd709d 100644
--- a/Mesh.cpp
+++ b/Mesh.cpp
@@ -1,6 +1,7 @@
 #include "Mesh.hpp"
 
 Mesh::Mesh()
+    : center(Point(.0, .0, .0))
 {
 }
 
@@ -16,6 +17,32 @@ void Mesh::add_face(size_t f1, size_t f2, size_t f3) {
     add_face(Face(f1, f2, f3));
 }
 
+const Point& Mesh::get_center() const {
+    return center;
+}
+
+void Mesh::set_center(const Point& pt) {
+    center = pt;
+}
+void Mesh::translate(const Point& tr) {
+    center += tr;
+}
+
+void Mesh::normalize_center(bool keep_position) {
+    Point bary(0., 0., 0.);
+    for(const Point& vert: vertices)
+        bary += vert;
+    bary = (1. / ((double)vertices.size())) * bary;
+
+    for(Point& vert: vertices)
+        vert -= bary;
+
+    if(keep_position)
+        translate(bary);
+    else
+        set_center(Point(0, 0, 0));
+}
+
 const std::vector<Point>& Mesh::get_vertices() const {
     return vertices;
 }
diff --git a/Mesh.hpp b/Mesh.hpp
index e46c127..43d668f 100644
--- a/Mesh.hpp
+++ b/Mesh.hpp
@@ -20,6 +20,17 @@ class Mesh {
         void add_face(const Face& face);
         void add_face(size_t f1, size_t f2, size_t f3);
 
+        /// Center manipulation
+        const Point& get_center() const;
+        void set_center(const Point& pt);
+        void translate(const Point& tr); ///< Translate by the vector `tr`
+
+        /** Translates the vertices to make (0, 0, 0) the mesh's barycenter.
+         * If `keep_position == true`, this also sets the center to the
+         * previous barycenter.
+         */
+        void normalize_center(bool keep_position=false);
+
         /// Gets the various vertices
         const std::vector<Point>& get_vertices() const;
 
@@ -29,4 +40,6 @@ class Mesh {
     private:
         std::vector<Point> vertices;
         std::vector<Face> faces;
+
+        Point center;
 };
diff --git a/common_structures.hpp b/common_structures.hpp
index 8c88a13..adf9d9f 100644
--- a/common_structures.hpp
+++ b/common_structures.hpp
@@ -21,6 +21,30 @@ struct Point {
             default:    return 0;
         }
     }
+
+    Point operator+(const Point& pt) const {
+        return Point(
+                x + pt.x,
+                y + pt.y,
+                z + pt.z);
+    }
+    Point& operator+=(const Point& pt) {
+        x += pt.x;
+        y += pt.y;
+        z += pt.z;
+        return *this;
+    }
+
+    Point& operator-=(const Point& pt) {
+        return (*this += Point(-pt.x, -pt.y, -pt.z));
+    }
+
+    friend Point operator*(double scalar, const Point& pt) {
+        return Point(
+                scalar * pt.x,
+                scalar * pt.y,
+                scalar * pt.z);
+    }
 };
 
 struct Face {