feat(meshIO): added linear rescale capability to meshIO

loaded meshes can be linearly rescaled (so for example a unit sphere can be rescaled to a sphere of any radius)

src/meshIO/private/meshIO.cpp

@@ -2,7 +2,7 @@
 //
 //   Copyright (C) 2025 -- The 4D-STAR Collaboration
 //   File Author: Emily Boudreaux
-//   Last Modified: February 16, 2025
+//   Last Modified: March 18, 2025
 //
 //   4DSSE is free software; you can use it and/or modify
 //   it under the terms and restrictions the GNU General Library Public
@@ -22,11 +22,12 @@
 #include <string>
 #include <iostream>
 #include <fstream>
+#include <stdexcept>
 
 #include "meshIO.h"
 
 
-MeshIO::MeshIO(const std::string mesh_file)
+MeshIO::MeshIO(const std::string &mesh_file, double scale_factor)
 {
     mesh_file_ = mesh_file;
     std::ifstream mesh_stream(mesh_file);
@@ -37,8 +38,9 @@ MeshIO::MeshIO(const std::string mesh_file)
     }
     else
     {
-        mesh_ = mfem::Mesh(mesh_stream, 1, 2);
+        mesh_ = mfem::Mesh(mesh_stream, 1, 10);
         loaded_ = true;
+        if (scale_factor != 1.0) { LinearRescale(scale_factor); }
     }
 }
 
@@ -46,6 +48,32 @@ MeshIO::~MeshIO()
 {
 }
 
+void MeshIO::LinearRescale(double scale_factor) {
+    if (!loaded_) {
+        throw std::runtime_error("Mesh not loaded before rescaling.");
+    }
+
+    if (scale_factor <= 0.0) {
+        throw std::invalid_argument("Scale factor must be positive.");
+    }
+
+    // Ensure there are nodes even for linear order meshes
+    mesh_.EnsureNodes();
+    const mfem::GridFunction *nodes = mesh_.GetNodes();
+    double *node_data = nodes->GetData();  // THIS IS KEY
+
+    int data_size = nodes->Size();
+
+    for (int i = 0; i < data_size; ++i) {
+        node_data[i] *= scale_factor;
+    }
+
+    // nodes->Update(); /updates the fespace
+    mesh_.NodesUpdated();
+ 
+
+}
+
 bool MeshIO::IsLoaded() const
 {
     return loaded_;

src/meshIO/public/meshIO.h

@@ -2,7 +2,7 @@
 //
 //   Copyright (C) 2025 -- The 4D-STAR Collaboration
 //   File Author: Emily Boudreaux
-//   Last Modified: February 16, 2025
+//   Last Modified: March 18, 2025
 //
 //   4DSSE is free software; you can use it and/or modify
 //   it under the terms and restrictions the GNU General Library Public
@@ -39,13 +39,19 @@ public:
      * @brief Constructor that initializes the MeshIO object with a mesh file.
      * @param mesh_file The name of the mesh file.
      */
-    MeshIO(const std::string mesh_file);
+    MeshIO(const std::string &mesh_file, double scale_factor = 1.0);
 
     /**
      * @brief Destructor for the MeshIO class.
      */
     ~MeshIO();
 
+    /**
+     * @brief Rescale the mesh by a linear factor.
+     * @param scale_factor The factor by which to scale the mesh.
+     */
+    void LinearRescale(double scale_factor);
+
     /**
      * @brief Get the mesh object.
      * @return Reference to the mesh object.