the_grid_transform.hxx

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 University of Utah.
 
 
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// File         : the_grid_transform.hxx
// Author       : Pavel A. Koshevoy
// Created      : Thu Nov 30 10:45:47 MST 2006
// Copyright    : (C) 2004-2008 University of Utah
// Description  : A discontinuous transform -- a uniform grid of vertices is
//                mapped to an image. At each vertex, in addition to image
//                space coordinates, a second set of coordinates is stored.
//                This is similar to texture mapped OpenGL triangle meshes,
//                where the texture coordinates correspond to the image space
//                vertex coordinates.

#ifndef THE_GRID_TRANSFORM_HXX_
#define THE_GRID_TRANSFORM_HXX_

// local includes:
#include <Core/ITKCommon/common.hxx>

// system includes:
#include <vector>
#include <list>


//----------------------------------------------------------------
// vertex_t
// 
class vertex_t
{
public:
  // normalized tile space coordinates, typically [0, 1] x [0, 1]:
  pnt2d_t uv_;
  
  // physical space coordinates:
  pnt2d_t xy_;
};

//----------------------------------------------------------------
// triangle_t
// 
class triangle_t
{
public:
  triangle_t();
  
  // check whether a given xy-point falls within this triangle,
  // return corresponding uv-point (not triangle barycentric coordinates):
  bool xy_intersect(const vertex_t * v_arr,
                    const pnt2d_t & xy,
                    pnt2d_t & uv) const;
  
  // check whether a given uv-point falls within this triangle,
  // return corresponding xy-point  (not triangle barycentric coordinates):
  bool uv_intersect(const vertex_t * v_arr,
                    const pnt2d_t & uv,
                    pnt2d_t & xy) const;
  
  // triangle vertex indices, counterclockwise winding:
  unsigned int vertex_[3];
  
  // precomputed fast barycentric coordinate calculation coefficients:
  
  // for intersection calculation in xy-space:
  double xy_pwb[3];
  double xy_pwc[3];
  
  // for intersection calculation in uv-space:
  double uv_pwb[3];
  double uv_pwc[3];
};

//----------------------------------------------------------------
// the_acceleration_grid_t
//
// The bounding grid triangle/point intersection acceleration
// structure used to speed up grid transform and mesh transform:
// 
class the_acceleration_grid_t
{
public:
  the_acceleration_grid_t();
  
  // find the grid cell containing a given xy-point:
  unsigned int xy_cell(const pnt2d_t & xy) const;
  
  // find the triangle containing a given xy-point,
  // and calculate corresponding uv-point:
  unsigned int xy_triangle(const pnt2d_t & xy, pnt2d_t & uv) const;
  
  // find the grid cell containing a given uv-point:
  unsigned int uv_cell(const pnt2d_t & uv) const;
  
  // find the triangle containing a given uv-point,
  // and calculate corresponding xy-point:
  unsigned int uv_triangle(const pnt2d_t & uv, pnt2d_t & xy) const;
  
  // update the vertex xy coordinates and rebuild the grid
  void update(const vec2d_t * xy_shift);
  void shift(const vec2d_t & xy_shift);

  // resize the grid:
  void resize(unsigned int rows,
              unsigned int cols);
  
  // rebuild the acceleration grid:
  void rebuild();
  
private:
  // helper used to rebuild the grid:
  void update_grid(unsigned int t_idx);
  
public:  
  // the acceleration structure:
  std::vector<std::list<unsigned int> > xy_;
  std::vector<std::list<unsigned int> > uv_;
  unsigned int rows_;
  unsigned int cols_;
  
  // the grid bounding box (in xy-space):
  pnt2d_t xy_min_;
  vec2d_t xy_ext_;
  
  // the triangle mesh:
  std::vector<vertex_t> mesh_;
  std::vector<triangle_t> tri_;
};


//----------------------------------------------------------------
// the_base_triangle_transform_t
// 
class the_base_triangle_transform_t
{
public:
  // transform the point:
  bool transform(const pnt2d_t & xy, pnt2d_t & uv) const;
  
  // inverse transform the point:
  bool transform_inv(const pnt2d_t & uv, pnt2d_t & xy) const;
  
  // calculate the derivatives of the transforms with respect to
  // transform parameters:
  bool jacobian(const pnt2d_t & xy, unsigned int * idx, double * jac) const;
  
public:
  // tile bounding box:
  pnt2d_t tile_min_;
  vec2d_t tile_ext_;
  
  // the acceleration grid (stores triangle vertices, and triangles):
  the_acceleration_grid_t grid_;
};


//----------------------------------------------------------------
// the_grid_transform_t
// 
class the_grid_transform_t : public the_base_triangle_transform_t
{
public:
  the_grid_transform_t();
  
  // check to see whether the transform has already been setup:
  bool is_ready() const;
  
  // vertex accessors:
  inline const vertex_t & vertex(size_t row, size_t col) const
  { return grid_.mesh_[row * (cols_ + 1) + col]; }
  
  inline vertex_t & vertex(size_t row, size_t col)
  { return grid_.mesh_[row * (cols_ + 1) + col]; }
  
  // inverse transform the point:
  bool transform_inv(const pnt2d_t & uv, pnt2d_t & xy) const;
  
  // setup the transform:
  void setup(unsigned int rows,
             unsigned int cols,
             const pnt2d_t & tile_min,
             const pnt2d_t & tile_max,
             const std::vector<pnt2d_t> & xy);
  
private:
  // helper used to setup the triangle mesh:
  void setup_mesh();
  
public:
  // number of rows and columns of quads in the mesh
  // (each quad is made up of 2 triangles):
  size_t rows_;
  size_t cols_;
};


//----------------------------------------------------------------
// the_mesh_transform_t
// 
class the_mesh_transform_t : public the_base_triangle_transform_t
{
public:
  // check to see whether the transform has already been setup:
  bool is_ready() const;
  
  // setup the transform:
  bool setup(const pnt2d_t & tile_min,
             const pnt2d_t & tile_max,
             const std::vector<pnt2d_t> & uv,
             const std::vector<pnt2d_t> & xy,
             unsigned int accel_grid_rows = 16,
             unsigned int accel_grid_cols = 16);
  
  // insert a point into the mesh, and re-triangulate
  // using Delaunay triangulation:
  bool insert_point(const pnt2d_t & uv,
                    const pnt2d_t & xy,
                    const bool delay_setup = false);

  // insert a point into the mesh (xy-point is extrapolated),
  // and re-triangulate using Delaunay triangulation:
  bool insert_point(const pnt2d_t & uv);
  
private:
  // helper used to setup the triangle mesh:
  bool setup_mesh();
};


#endif // THE_GRID_TRANSFORM_HXX_