/*!\file gr3_mc.c
 *
 * Optimized OpenMP implementation of the marching cubes algorithm.
 *
 * This code is based on Paul Bourke's Marching Cubes implementation
 * (http://paulbourke.net/geometry/polygonise/)
 *
 * Creates an indexed mesh to reduce the number of vertices to calculate.
 * This is done by caching generated vertices depending on their location.
 * Multiple threads create independent meshes.
 * Caches values between adjacent cubes.
 *
 * Fabian Beule
 * 2014-02-10
 */

#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "gr3.h"
#include "gr3_mc_data.h"
#ifdef _OPENMP
#include <omp.h>
#endif

#define ABS(x) ((x) < 0 ? -(x) : (x))
#define INDEX(x, y, z) ((x) * mcdata.stride[0] + (y) * mcdata.stride[1] + (z) * mcdata.stride[2])
#define IDX2D(y, z) ((y) * mcdata.dim[2] + (z))

/* speedup does not grow much with a high number of threads */
#define THREADLIMIT 16

/* for smaller function headers */
typedef struct
{
  const GR3_MC_DTYPE *data;
  GR3_MC_DTYPE isolevel;
  int dim[3];
  int stride[3];
  double step[3];
  double offset[3];
} mcdata_t;

/* calculate the gradient via difference qoutient */
static gr3_coord_t getgrad(mcdata_t mcdata, int x, int y, int z)
{
  int v[3];
  int neigh[3][2];
  int i;
  gr3_coord_t n;

  v[0] = x;
  v[1] = y;
  v[2] = z;

  for (i = 0; i < 3; i++)
    {
      if (v[i] > 0)
        neigh[i][0] = v[i] - 1;
      else
        neigh[i][0] = v[i];
      if (v[i] < mcdata.dim[i] - 1)
        neigh[i][1] = v[i] + 1;
      else
        neigh[i][1] = v[i];
    }
  n.x = (float)(mcdata.data[INDEX(neigh[0][1], y, z)] - mcdata.data[INDEX(neigh[0][0], y, z)]) /
        (neigh[0][1] - neigh[0][0]) / mcdata.step[0];
  n.y = (float)(mcdata.data[INDEX(x, neigh[1][1], z)] - mcdata.data[INDEX(x, neigh[1][0], z)]) /
        (neigh[1][1] - neigh[1][0]) / mcdata.step[1];
  n.z = (float)(mcdata.data[INDEX(x, y, neigh[2][1])] - mcdata.data[INDEX(x, y, neigh[2][0])]) /
        (neigh[2][1] - neigh[2][0]) / mcdata.step[2];

  return n;
}

/* interpolate points and calulate normals */
static void interpolate(mcdata_t mcdata, int px, int py, int pz, GR3_MC_DTYPE v1, int qx, int qy, int qz,
                        GR3_MC_DTYPE v2, gr3_coord_t *p, gr3_coord_t *n)
{
  double mu;
  gr3_coord_t n1, n2;
  double norm;

  if (ABS(mcdata.isolevel - v1) < 0.00001)
    mu = 0.0;
  else if (ABS(mcdata.isolevel - v2) < 0.00001)
    mu = 1.0;
  else if (ABS(v1 - v2) < 0.00001)
    mu = 0.5;
  else
    mu = 1.0 * (mcdata.isolevel - v1) / (v2 - v1);

  p->x = (px + mu * (qx - px)) * mcdata.step[0] + mcdata.offset[0];
  p->y = (py + mu * (qy - py)) * mcdata.step[1] + mcdata.offset[1];
  p->z = (pz + mu * (qz - pz)) * mcdata.step[2] + mcdata.offset[2];

  n1 = getgrad(mcdata, px, py, pz);
  n2 = getgrad(mcdata, qx, qy, qz);
  n->x = -(n1.x + mu * (n2.x - n1.x));
  n->y = -(n1.y + mu * (n2.y - n1.y));
  n->z = -(n1.z + mu * (n2.z - n1.z));

  norm = sqrt(n->x * n->x + n->y * n->y + n->z * n->z);
  if (norm > 0.0)
    {
      n->x /= norm;
      n->y /= norm;
      n->z /= norm;
    }
}

/*!
 * marching cubes algorithm for one x-layer.
 * created vertices are cached between calls using vindex.
 * vindex associates the intersected edge with the vertex index.
 * the edge is identified by its location (low, high), direction (x, y, z)
 * and coordinates (py, pz) of its starting point.
 * direction and location are the first index:
 * (x, y_low, z_low, y_high, z_high) (see mc_edgeprop)
 * second index is py * mcdata.dim[1] + pz.
 * py and pz are the coordinates of the lower one of both edge vertices
 */
static void layer(mcdata_t mcdata, int x, int **vindex, unsigned int *num_vertices, gr3_coord_t **vertices,
                  gr3_coord_t **normals, unsigned int *vertcapacity, unsigned int *num_faces, unsigned int **indices,
                  unsigned int *facecapacity)
{
  int i, j;
  int y, z;
  int cubeindex;
  GR3_MC_DTYPE cubeval[8]; /* also cache between adjacent cubes */

  for (y = 0; y < mcdata.dim[1] - 1; y++)
    {
      /* init z-cache */
      for (i = 0; i < 4; i++)
        {
          int zi = mc_zvertices[0][i];

          cubeval[mc_zvertices[1][i]] =
              mcdata.data[INDEX(x + mc_cubeverts[zi][0], y + mc_cubeverts[zi][1], 0 + mc_cubeverts[zi][2])];
        }
      for (z = 0; z < mcdata.dim[2] - 1; z++)
        {
          cubeindex = 0;
          /* shift old values (z-cache) */
          for (i = 0; i < 4; i++)
            {
              int zi = mc_zvertices[0][i];

              cubeval[zi] = cubeval[mc_zvertices[1][i]];
              if (cubeval[zi] < mcdata.isolevel)
                {
                  cubeindex |= 1 << zi;
                }
            }
          /* read new cube values */
          for (i = 0; i < 4; i++)
            {
              int zi = mc_zvertices[1][i];

              cubeval[zi] =
                  mcdata.data[INDEX(x + mc_cubeverts[zi][0], y + mc_cubeverts[zi][1], z + mc_cubeverts[zi][2])];
              if (cubeval[zi] < mcdata.isolevel)
                {
                  cubeindex |= 1 << zi;
                }
            }
          if (cubeindex != 0 && cubeindex != 255)
            {
              /* create triangles */
              for (i = 0; i < mc_tricount[cubeindex]; i++)
                {
                  if (*facecapacity <= *num_faces)
                    {
                      (*facecapacity) = (unsigned int)(*num_faces * 1.5) + 50;
                      *indices = realloc(*indices, (*facecapacity) * 3 * sizeof(int));
                    }
                  /* create triangle vertices */
                  for (j = 0; j < 3; j++)
                    {
                      int trival = mc_tritable[cubeindex][i * 3 + j];
                      const int *edge = mc_cubeedges[trival];
                      int dir = mc_edgeprop[trival];
                      int px = x + mc_cubeverts[edge[0]][0];
                      int py = y + mc_cubeverts[edge[0]][1];
                      int pz = z + mc_cubeverts[edge[0]][2];
                      /* lookup if vertex already exists */
                      int node = vindex[dir][IDX2D(py, pz)];
                      if (node < 0)
                        {
                          /* it does not, create it */
                          GR3_MC_DTYPE v1 = cubeval[edge[0]];
                          GR3_MC_DTYPE v2 = cubeval[edge[1]];
                          if (*vertcapacity <= *num_vertices)
                            {
                              (*vertcapacity) = (unsigned int)(*num_vertices * 1.5) + 50;
                              *vertices = realloc(*vertices, (*vertcapacity) * sizeof(gr3_coord_t));
                              *normals = realloc(*normals, (*vertcapacity) * sizeof(gr3_coord_t));
                            }
                          node = *num_vertices;
                          interpolate(mcdata, px, py, pz, v1, x + mc_cubeverts[edge[1]][0],
                                      y + mc_cubeverts[edge[1]][1], z + mc_cubeverts[edge[1]][2], v2, *vertices + node,
                                      *normals + node);
                          vindex[dir][IDX2D(py, pz)] = node;
                          (*num_vertices)++;
                        }
                      /* add vertex index to the element array */
                      (*indices)[*num_faces * 3 + j] = node;
                    }
                  (*num_faces)++;
                }
            }
        }
    }
}

/*!
 * handle consecutive calls to layer
 */
static void layerblock(mcdata_t mcdata, int from, int to, unsigned int *num_vertices, gr3_coord_t **vertices,
                       gr3_coord_t **normals, unsigned int *num_faces, unsigned int **faces)
{
  int x;
  int y;
  int z;
  unsigned int vertcapacity;
  unsigned int facecapacity;
  /* cache for the vertex indices of the x-layer
   * [x, y_bot, z_bot, y_top, z_top] */
  int *vindex[5], *ntmp;

  *num_vertices = 0;
  vertcapacity = 0;
  *vertices = NULL;
  *normals = NULL;
  *num_faces = 0;
  facecapacity = 0;
  *faces = NULL;

  vindex[0] = malloc(5 * mcdata.dim[1] * mcdata.dim[2] * sizeof(int));
  vindex[1] = vindex[0] + mcdata.dim[1] * mcdata.dim[2];
  vindex[2] = vindex[0] + 2 * mcdata.dim[1] * mcdata.dim[2];
  vindex[3] = vindex[0] + 3 * mcdata.dim[1] * mcdata.dim[2];
  vindex[4] = vindex[0] + 4 * mcdata.dim[1] * mcdata.dim[2];

  for (y = 0; y < mcdata.dim[1]; y++)
    {
      for (z = 0; z < mcdata.dim[2]; z++)
        {
          vindex[0][IDX2D(y, z)] = -1;
          vindex[3][IDX2D(y, z)] = -1;
          vindex[4][IDX2D(y, z)] = -1;
        }
    }
  /*
   * iterate layer-by-layer through the data
   * create an indexed mesh
   * indices are cached in vindex[direction of the edge][y, z]
   * the top cache becomes the bottom in the next iterarion
   */
  for (x = from; x < to; x++)
    {
      ntmp = vindex[1];
      vindex[1] = vindex[3];
      vindex[3] = ntmp;
      ntmp = vindex[2];
      vindex[2] = vindex[4];
      vindex[4] = ntmp;
      for (y = 0; y < mcdata.dim[1]; y++)
        {
          for (z = 0; z < mcdata.dim[2]; z++)
            {
              vindex[0][IDX2D(y, z)] = -1;
              vindex[3][IDX2D(y, z)] = -1;
              vindex[4][IDX2D(y, z)] = -1;
            }
        }
      layer(mcdata, x, vindex, num_vertices, vertices, normals, &vertcapacity, num_faces, faces, &facecapacity);
    }
  free(vindex[0]);
}

/*!
 * Create an isosurface (as indexed mesh) from voxel data
 * with the marching cubes algorithm.
 * This function manages the parallelization:
 * Divide the data into blocks along the x-axis. Allocate memory,
 * call layerblock and merge the individual meshes into a single one.
 *
 * \param [in]  data          the volume (voxel) data
 * \param [in]  isolevel      value where the isosurface will be extracted
 * \param [in]  dim_x         number of elements in x-direction
 * \param [in]  dim_y         number of elements in y-direction
 * \param [in]  dim_z         number of elements in z-direction
 * \param [in]  stride_x      number of elements to step when traversing
 *                            the data in x-direction
 * \param [in]  stride_y      number of elements to step when traversing
 *                            the data in y-direction
 * \param [in]  stride_z      number of elements to step when traversing
 *                            the data in z-direction
 * \param [in]  step_x        distance between the voxels in x-direction
 * \param [in]  step_y        distance between the voxels in y-direction
 * \param [in]  step_z        distance between the voxels in z-direction
 * \param [in]  offset_x      coordinate origin
 * \param [in]  offset_y      coordinate origin
 * \param [in]  offset_z      coordinate origin
 * \param [out] num_vertices  number of vertices created
 * \param [out] vertices      array of vertex coordinates
 * \param [out] normals       array of vertex normal vectors
 * \param [out] num_indices   number of indices created
 *                            (3 times the number of triangles)
 * \param [out] indices       array of vertex indices that make the triangles
 */
GR3API void gr3_triangulateindexed(const GR3_MC_DTYPE *data, GR3_MC_DTYPE isolevel, unsigned int dim_x,
                                   unsigned int dim_y, unsigned int dim_z, unsigned int stride_x, unsigned int stride_y,
                                   unsigned int stride_z, double step_x, double step_y, double step_z, double offset_x,
                                   double offset_y, double offset_z, unsigned int *num_vertices, gr3_coord_t **vertices,
                                   gr3_coord_t **normals, unsigned int *num_indices, unsigned int **indices)
{
  int num_threads;
  unsigned int num_faces;
  unsigned int *num_t_vertices, *num_t_faces, **t_faces;
  gr3_coord_t **t_vertices, **t_normals;
  unsigned int *vertblock, *faceblock;
  mcdata_t mcdata;
#if defined(_OPENMP) && defined(THREADLIMIT)
  int max_threads;

  max_threads = omp_get_max_threads();
  if (max_threads > THREADLIMIT) omp_set_num_threads(THREADLIMIT);
#endif

  if (stride_x == 0) stride_x = dim_z * dim_y;
  if (stride_y == 0) stride_y = dim_z;
  if (stride_z == 0) stride_z = 1;

  mcdata.data = data;
  mcdata.isolevel = isolevel;
  mcdata.dim[0] = dim_x;
  mcdata.dim[1] = dim_y;
  mcdata.dim[2] = dim_z;
  mcdata.stride[0] = stride_x;
  mcdata.stride[1] = stride_y;
  mcdata.stride[2] = stride_z;
  mcdata.step[0] = step_x;
  mcdata.step[1] = step_y;
  mcdata.step[2] = step_z;
  mcdata.offset[0] = offset_x;
  mcdata.offset[1] = offset_y;
  mcdata.offset[2] = offset_z;

  *num_vertices = 0;
  *vertices = NULL;
  *normals = NULL;
  *num_indices = 0;
  *indices = NULL;

#ifdef _OPENMP
#pragma omp parallel default(none)                                                                                 \
    shared(num_threads, num_t_vertices, t_vertices, t_normals, num_t_faces, t_faces, mcdata, vertblock, faceblock, \
               num_vertices, num_faces, vertices, normals, indices)
#endif
  {
    int thread_id;
    unsigned int from, to;
    unsigned int i;
#ifdef _OPENMP
#pragma omp single
#endif
    {
      /* allocate temporary memory for each thread */
#ifdef _OPENMP
      num_threads = omp_get_num_threads();
#else
      num_threads = 1;
#endif
      num_t_vertices = malloc(num_threads * sizeof(unsigned int));
      t_vertices = malloc(num_threads * sizeof(gr3_coord_t *));
      t_normals = malloc(num_threads * sizeof(gr3_coord_t *));
      num_t_faces = malloc(num_threads * sizeof(unsigned int));
      t_faces = malloc(num_threads * sizeof(unsigned int *));
    }
    /* create a mesh per thread */
#ifdef _OPENMP
    thread_id = omp_get_thread_num();
#else
    thread_id = 0;
#endif
    from = thread_id * (mcdata.dim[0] - 1) / num_threads;
    to = (thread_id + 1) * (mcdata.dim[0] - 1) / num_threads;
    num_t_vertices[thread_id] = 0;
    t_vertices[thread_id] = NULL;
    t_normals[thread_id] = NULL;
    num_t_faces[thread_id] = 0;
    t_faces[thread_id] = NULL;
    layerblock(mcdata, from, to, num_t_vertices + thread_id, t_vertices + thread_id, t_normals + thread_id,
               num_t_faces + thread_id, t_faces + thread_id);
#ifdef _OPENMP
#pragma omp barrier
#pragma omp single
#endif
    {
      /* calculate beginning indices of thread blocks */
      vertblock = malloc((num_threads + 1) * sizeof(unsigned int));
      vertblock[0] = 0;
      faceblock = malloc((num_threads + 1) * sizeof(unsigned int));
      faceblock[0] = 0;
      for (i = 0; i < (unsigned int)num_threads; i++)
        {
          vertblock[i + 1] = vertblock[i] + num_t_vertices[i];
          faceblock[i + 1] = faceblock[i] + num_t_faces[i];
        }
      *num_vertices = vertblock[num_threads];
      num_faces = faceblock[num_threads];
      *vertices = realloc(*vertices, *num_vertices * sizeof(gr3_coord_t));
      *normals = realloc(*normals, *num_vertices * sizeof(gr3_coord_t));
      *indices = realloc(*indices, num_faces * 3 * sizeof(unsigned int));
    }
    /* copy thread meshes into the arrays */
    memmove(*vertices + vertblock[thread_id], t_vertices[thread_id], num_t_vertices[thread_id] * sizeof(gr3_coord_t));
    memmove(*normals + vertblock[thread_id], t_normals[thread_id], num_t_vertices[thread_id] * sizeof(gr3_coord_t));
    /* translate thread indices to global indices */
    for (i = 0; i < num_t_faces[thread_id]; i++)
      {
        (*indices)[(faceblock[thread_id] + i) * 3 + 0] = t_faces[thread_id][i * 3 + 0] + vertblock[thread_id];
        (*indices)[(faceblock[thread_id] + i) * 3 + 1] = t_faces[thread_id][i * 3 + 1] + vertblock[thread_id];
        (*indices)[(faceblock[thread_id] + i) * 3 + 2] = t_faces[thread_id][i * 3 + 2] + vertblock[thread_id];
      }
    free(t_vertices[thread_id]);
    free(t_normals[thread_id]);
    free(t_faces[thread_id]);
  }
  free(faceblock);
  free(vertblock);
  free(t_faces);
  free(num_t_faces);
  free(t_normals);
  free(t_vertices);
  free(num_t_vertices);
  *num_indices = num_faces * 3;
#if defined(_OPENMP) && defined(THREADLIMIT)
  omp_set_num_threads(max_threads);
#endif
}

/*!
 * Create an isosurface (as mesh) from voxel data
 * with the marching cubes algorithm.
 * This function calls gr3_triangulateindexed and copies the values.
 *
 * \param [in]  data          the volume (voxel) data
 * \param [in]  isolevel      value where the isosurface will be extracted
 * \param [in]  dim_x         number of elements in x-direction
 * \param [in]  dim_y         number of elements in y-direction
 * \param [in]  dim_z         number of elements in z-direction
 * \param [in]  stride_x      number of elements to step when traversing
 *                           the data in x-direction
 * \param [in]  stride_y      number of elements to step when traversing
 *                           the data in y-direction
 * \param [in]  stride_z      number of elements to step when traversing
 *                           the data in z-direction
 * \param [in]  step_x        distance between the voxels in x-direction
 * \param [in]  step_y        distance between the voxels in y-direction
 * \param [in]  step_z        distance between the voxels in z-direction
 * \param [in]  offset_x      coordinate origin
 * \param [in]  offset_y      coordinate origin
 * \param [in]  offset_z      coordinate origin
 * \param [out] triangles_p   array of triangle data
 *
 * \returns the number of triangles created
 */
GR3API unsigned int gr3_triangulate(const GR3_MC_DTYPE *data, GR3_MC_DTYPE isolevel, unsigned int dim_x,
                                    unsigned int dim_y, unsigned int dim_z, unsigned int stride_x,
                                    unsigned int stride_y, unsigned int stride_z, double step_x, double step_y,
                                    double step_z, double offset_x, double offset_y, double offset_z,
                                    gr3_triangle_t **triangles_p)
{
  unsigned int num_vertices;
  gr3_coord_t *vertices, *normals;
  unsigned int num_indices;
  unsigned int *indices;
  unsigned int i, j;
#if defined(_OPENMP) && defined(THREADLIMIT)
  int max_threads;

  max_threads = omp_get_max_threads();
  if (max_threads > THREADLIMIT) omp_set_num_threads(THREADLIMIT);
#endif

  gr3_triangulateindexed(data, isolevel, dim_x, dim_y, dim_z, stride_x, stride_y, stride_z, step_x, step_y, step_z,
                         offset_x, offset_y, offset_z, &num_vertices, &vertices, &normals, &num_indices, &indices);

  *triangles_p = malloc(num_indices / 3 * sizeof(gr3_triangle_t));
#ifdef _OPENMP
#pragma omp parallel for default(none) private(j) shared(num_indices, triangles_p, indices, vertices, normals)
#endif
  for (i = 0; i < num_indices / 3; i++)
    {
      for (j = 0; j < 3; j++)
        {
          (*triangles_p)[i].vertex[j] = vertices[indices[i * 3 + j]];
          (*triangles_p)[i].normal[j] = normals[indices[i * 3 + j]];
        }
    }
  free(vertices);
  free(normals);
  free(indices);

#if defined(_OPENMP) && defined(THREADLIMIT)
  omp_set_num_threads(max_threads);
#endif
  return num_indices / 3;
}
