text: /*************************************************************************
   *                                                                       *
   * Vega FEM Simulation Library Version 4.0                               *
   *                                                                       *
   * "volumetricMesh" library , Copyright (C) 2007 CMU, 2009 MIT, 2018 USC *
   * All rights reserved.                                                  *
   *                                                                       *
   * Code authors: Jernej Barbic, Hongyi Xu                                *
   * http://www.jernejbarbic.com/vega                                      *
   *                                                                       *
   * Research: Jernej Barbic, Hongyi Xu, Yijing Li,                        *
   *           Danyong Zhao, Bohan Wang,                                   *
   *           Fun Shing Sin, Daniel Schroeder,                            *
   *           Doug L. James, Jovan Popovic                                *
   *                                                                       *
   * Funding: National Science Foundation, Link Foundation,                *
   *          Singapore-MIT GAMBIT Game Lab,                               *
   *          Zumberge Research and Innovation Fund at USC,                *
   *          Sloan Foundation, Okawa Foundation,                          *
   *          USC Annenberg Foundation                                     *
   *                                                                       *
   * This library is free software; you can redistribute it and/or         *
   * modify it under the terms of the BSD-style license that is            *
   * included with this library in the file LICENSE.txt                    *
   *                                                                       *
   * This library is distributed in the hope that it will be useful,       *
   * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the file     *
   * LICENSE.TXT for more details.                                         *
   *                                                                       *
   *************************************************************************/
  
  #ifndef _GENERATEGRADIENTMATRIX_H_
  #define _GENERATEGRADIENTMATRIX_H_
  
  #include "sparseMatrix.h"
  #include "tetMesh.h"
  
  // creates the sparse matrix G that computes the gradient
  // of a 3D vector field on a tet mesh
  // optionally, computes G^T G as well
  
  class GenerateGradientMatrix
  {
  public:
  
    // for a 3D vector field on a tet mesh
    // weights serve as GTw^2G
    static void Generate(const TetMesh * tetMesh, SparseMatrix ** G, SparseMatrix ** GTG = NULL, double * GTGElementWeights = NULL); // of the entire mesh 
  
    static void GenerateElementMatrix(const TetMesh * tetMesh, int el, double * G); // of a single element; G is 9 x 12
  
    // the version that operates on scalar fields
    static void GenerateForScalarField(const TetMesh * tetMesh, SparseMatrix ** GTG, double * GTGElementWeights); // of the entire mesh
  
  protected:
    static void GenerateElementMatrixEntries(const TetMesh * tetMesh, int el, double * m); // of a single element, condensed array "m" of 12 doubles
  };
  
  #endif
  
  