add Normals to meshes

src/Math/QuadMesh.cpp

@@ -60,5 +60,18 @@ void QuadMesh::AddQuad(const Vector4i &id)
     this->m_Quads.push_back(id);
 }
 
+Vector3f QuadMesh::GetNormal(const Id_t id) const
+{
+    const Vector4i &quad = m_Quads.at(id);
+    const Vector3f &v0 = m_Points.at(quad(0));
+    const Vector3f &v1 = m_Points.at(quad(1));
+    const Vector3f &v3 = m_Points.at(quad(3));
+    
+    Vector3f edge1 = v1 - v0;
+    Vector3f edge2 = v3 - v0;
+    
+    return edge1.cross(edge2).normalized();
+}
+
 
 }