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surface.c

/* pygts - python package for the manipulation of triangulated surfaces
 *
 *   Copyright (C) 2009 Thomas J. Duck
 *   All rights reserved.
 *
 *   Thomas J. Duck <tom.duck@dal.ca>
 *   Department of Physics and Atmospheric Science,
 *   Dalhousie University, Halifax, Nova Scotia, Canada, B3H 3J5
 *
 * NOTICE
 *
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Library General Public
 *   License as published by the Free Software Foundation; either
 *   version 2 of the License, or (at your option) any later version.
 *
 *   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 GNU
 *   Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this library; if not, write to the
 *   Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 *   Boston, MA 02111-1307, USA.
 */

#include "pygts.h"

#if PYGTS_DEBUG
  #define SELF_CHECK if(!pygts_surface_check((PyObject*)self)) {      \
                       PyErr_SetString(PyExc_RuntimeError,            \
                       "problem with self object (internal error)");  \
                   return NULL;                                   \
                     }
#else
  #define SELF_CHECK
#endif


/*-------------------------------------------------------------------------*/
/* Methods exported to python */

static PyObject*
is_ok(PygtsSurface *self, PyObject *args)
{
  if(pygts_surface_is_ok(self)) {
    Py_INCREF(Py_True);
    return Py_True;
  }
  else {
    Py_INCREF(Py_False);
    return Py_False;
  }
}


static PyObject*
add(PygtsSurface *self, PyObject *args)
{
  PyObject *o_;
  PygtsFace *f;
  PygtsSurface *s;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &o_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(pygts_face_check(o_)) {
    f = PYGTS_FACE(o_);
    gts_surface_add_face(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                   PYGTS_FACE_AS_GTS_FACE(f));

  }
  else if(pygts_surface_check(o_)) {
    s = PYGTS_SURFACE(o_);

    /* Make the call */
    gts_surface_merge(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                  PYGTS_SURFACE_AS_GTS_SURFACE(s));

  }
  else {
    PyErr_SetString(PyExc_TypeError,"expected a Face or a Surface");
    return NULL;
  }

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
pygts_remove(PygtsSurface *self, PyObject *args)
{
  PyObject *f_;
  PygtsFace *f;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &f_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_face_check(f_)) {
    PyErr_SetString(PyExc_TypeError,"expected a Face");
    return NULL;
  }
  f = PYGTS_FACE(f_);

  /* Make the call */
  gts_surface_remove_face(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                    PYGTS_FACE_AS_GTS_FACE(f));

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
copy(PygtsSurface *self, PyObject *args)
{
  PyObject *s_;
  PygtsSurface *s;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &s_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_surface_check(s_)) {
    PyErr_SetString(PyExc_TypeError,"expected a Surface");
    return NULL;
  }
  s = PYGTS_SURFACE(s_);

  /* Make the call */
  gts_surface_copy(PYGTS_SURFACE_AS_GTS_SURFACE(self),
               PYGTS_SURFACE_AS_GTS_SURFACE(s));

  Py_INCREF((PyObject*)self);
  return (PyObject*)self;
}


static PyObject*
is_manifold(PygtsSurface *self, PyObject *args)
{

  SELF_CHECK

  if( gts_surface_is_manifold(PYGTS_SURFACE_AS_GTS_SURFACE(self)) ) {
    Py_INCREF(Py_True);
    return Py_True;
  }
  else {
    Py_INCREF(Py_False);
    return Py_False;
  }
}


static PyObject*
manifold_faces(PygtsSurface *self, PyObject *args)
{
  PyObject *e_;
  PygtsEdge *e;
  GtsFace *f1,*f2;
  PygtsFace *face1,*face2;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &e_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_edge_check(e_)) {
    PyErr_SetString(PyExc_TypeError,"expected an Edge");
    return NULL;
  }
  e = PYGTS_EDGE(e_);

  /* Make the call */
  if(!gts_edge_manifold_faces(PYGTS_EDGE_AS_GTS_EDGE(e),
                        PYGTS_SURFACE_AS_GTS_SURFACE(self),
                        &f1, &f2)) {
    Py_INCREF(Py_None);
    return Py_None;
  }

  if( (face1 = pygts_face_new(f1)) == NULL ) {
    return NULL;
  }

  if( (face2 = pygts_face_new(f2)) == NULL ) {
    Py_DECREF(face1);
    return NULL;
  }

  return Py_BuildValue("OO",face1,face2);
}


static PyObject*
is_orientable(PygtsSurface *self, PyObject *args)
{
  SELF_CHECK

  if(gts_surface_is_orientable(PYGTS_SURFACE_AS_GTS_SURFACE(self))) {
    Py_INCREF(Py_True);
    return Py_True;
  }
  else {
    Py_INCREF(Py_False);
    return Py_False;
  }
}


static PyObject*
is_closed(PygtsSurface *self, PyObject *args)
{
  SELF_CHECK

  if(gts_surface_is_closed(PYGTS_SURFACE_AS_GTS_SURFACE(self))) {
    Py_INCREF(Py_True);
    return Py_True;
  }
  else {
    Py_INCREF(Py_False);
    return Py_False;
  }
}


static PyObject*
boundary(PyObject *self, PyObject *args)
{
  PyObject *tuple;
  guint i,N;
  GSList *edges=NULL,*e;
  PygtsEdge *edge;

  SELF_CHECK

  /* Make the call */
    if( (edges = gts_surface_boundary(PYGTS_SURFACE_AS_GTS_SURFACE(self))) 
      == NULL ) {
    PyErr_SetString(PyExc_RuntimeError,"could not retrieve edges");
    return NULL;
  }

  /* Assemble the return tuple */
  N = g_slist_length(edges);
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }
  e = edges;
  for(i=0;i<N;i++) {
    if( (edge = pygts_edge_new(GTS_EDGE(e->data))) == NULL ) {
      Py_DECREF(tuple);
      g_slist_free(edges);
    }
    PyTuple_SET_ITEM(tuple,i,(PyObject*)edge);
    e = g_slist_next(e);
  }

  g_slist_free(edges);

  return tuple;
}


static PyObject*
area(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;

  SELF_CHECK

  s = PYGTS_SURFACE_AS_GTS_SURFACE(self);
  return Py_BuildValue("d",gts_surface_area(s));
}


static PyObject*
volume(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;

  SELF_CHECK

  s = PYGTS_SURFACE_AS_GTS_SURFACE(self);

  if(!gts_surface_is_closed(s)) {
    PyErr_SetString(PyExc_RuntimeError,"Surface is not closed");
    return NULL;
  }

  if(!gts_surface_is_orientable(s)) {
    PyErr_SetString(PyExc_RuntimeError,"Surface is not orientable");
    return NULL;
  }

  return Py_BuildValue("d",gts_surface_volume(s));
}


static PyObject*
center_of_mass(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;
  GtsVector cm;

  SELF_CHECK

  s = PYGTS_SURFACE_AS_GTS_SURFACE(self);
  gts_surface_center_of_mass(s,cm);
  return Py_BuildValue("ddd",cm[0],cm[1],cm[2]);
}


static PyObject*
center_of_area(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;
  GtsVector cm;

  SELF_CHECK

  s = PYGTS_SURFACE_AS_GTS_SURFACE(self);
  gts_surface_center_of_area(s,cm);
  return Py_BuildValue("ddd",cm[0],cm[1],cm[2]);
}


static PyObject*
pygts_write(PygtsSurface *self, PyObject *args)
{
  PyObject *f_;
  FILE *f;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &f_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!PyFile_Check(f_)) {
    PyErr_SetString(PyExc_TypeError,"expected a File");
    return NULL;
  }
  f = PyFile_AsFile(f_);

  /* Write to the file */
  gts_surface_write(PYGTS_SURFACE_AS_GTS_SURFACE(self),f);

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
pygts_write_oogl(PygtsSurface *self, PyObject *args)
{
  PyObject *f_;
  FILE *f;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &f_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!PyFile_Check(f_)) {
    PyErr_SetString(PyExc_TypeError,"expected a File");
    return NULL;
  }
  f = PyFile_AsFile(f_);

  /* Write to the file */
  gts_surface_write_oogl(PYGTS_SURFACE_AS_GTS_SURFACE(self),f);

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
pygts_write_oogl_boundary(PygtsSurface *self, PyObject *args)
{
  PyObject *f_;
  FILE *f;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &f_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!PyFile_Check(f_)) {
    PyErr_SetString(PyExc_TypeError,"expected a File");
    return NULL;
  }
  f = PyFile_AsFile(f_);

  /* Write to the file */
  gts_surface_write_oogl_boundary(PYGTS_SURFACE_AS_GTS_SURFACE(self),f);

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
pygts_write_vtk(PygtsSurface *self, PyObject *args)
{
  PyObject *f_;
  FILE *f;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &f_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!PyFile_Check(f_)) {
    PyErr_SetString(PyExc_TypeError,"expected a File");
    return NULL;
  }
  f = PyFile_AsFile(f_);

  /* Write to the file */
  gts_surface_write_vtk(PYGTS_SURFACE_AS_GTS_SURFACE(self),f);

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
fan_oriented(PygtsSurface *self, PyObject *args)
{
  PyObject *v_;
  PygtsVertex *v;
  GSList *edges=NULL, *e;
  guint i,N;
  PyObject *tuple;
  PygtsEdge *edge;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &v_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_vertex_check(v_)) {
    PyErr_SetString(PyExc_TypeError,"expected a Vertex");
    return NULL;
  }
  v = PYGTS_VERTEX(v_);

  /* Check that the Surface is orientable; the calculation will
   * fail otherwise.
   */
  if(!gts_surface_is_orientable(PYGTS_SURFACE_AS_GTS_SURFACE(self))) {
    PyErr_SetString(PyExc_RuntimeError,"Surface must be orientable");
    return NULL;
  }

  /* Make the call */
  edges = gts_vertex_fan_oriented(PYGTS_VERTEX_AS_GTS_VERTEX(v),
                          PYGTS_SURFACE_AS_GTS_SURFACE(self));

  /* Build the return tuple */
  N = g_slist_length(edges);
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"Could not create tuple");
    return NULL;
  }
  e = edges;
  for(i=0;i<N;i++) {
    if( (edge = pygts_edge_new(GTS_EDGE(e->data))) == NULL ) {
      Py_DECREF(tuple);
      g_slist_free(edges);
      return NULL;
    }
    PyTuple_SET_ITEM(tuple,i,(PyObject*)edge);
    e = g_slist_next(e);
  }

  return tuple;
}


static PyObject*
split(PygtsSurface *self, PyObject *args)
{
  GSList *surfaces, *s;
  PyObject *tuple;
  PygtsSurface *surface;
  guint n,N;

  SELF_CHECK

  surfaces = gts_surface_split(PYGTS_SURFACE_AS_GTS_SURFACE(self));
  
  /* Create a tuple to put the Surfaces into */
  N = g_slist_length(surfaces);
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }

  /* Put PygtsSurface objects into the tuple */
  s = surfaces;
  for(n=0;n<N;n++) {
    if( (surface = pygts_surface_new(GTS_SURFACE(s->data))) == NULL ) {
      Py_DECREF(tuple);
      return NULL;
    }
    surface->traverse = NULL;
    PyTuple_SET_ITEM(tuple, n, (PyObject*)surface);
    s = g_slist_next(s);
  }

  return tuple;
}


/* Helper function for vertices() */
static void get_vertex(GtsVertex *vertex, GtsVertex ***v)
{
  **v = vertex;
  *v += 1;
}

static PyObject*
vertices(PygtsSurface *self, PyObject *args)
{
  PyObject *tuple;
  PygtsVertex *vertex;
  PygtsVertex **vertices,**v;
  guint i,N=0;

  SELF_CHECK

  /* Get the number of vertices */
  N = gts_surface_vertex_number(PYGTS_SURFACE_AS_GTS_SURFACE(self));

  /* Retrieve all of the vertex pointers into a temporary array */
  if( (vertices = (PygtsVertex**)malloc(N*sizeof(PygtsVertex*))) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"could not create array");
    return NULL;
  }
  v = vertices;

  gts_surface_foreach_vertex(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)get_vertex,&v);

  /* Create a tuple to put the vertices into */
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }

  /* Put PygtsVertex objects into the tuple */
  v = vertices;
  for(i=0;i<N;i++) {
    if( (vertex = pygts_vertex_new(GTS_VERTEX(*v))) == NULL ) {
      free(vertices);
      Py_DECREF(tuple);
      return NULL;
    }
    PyTuple_SET_ITEM(tuple, i, (PyObject*)vertex);    
    v += 1;
  }

  free(vertices);
  return tuple;
}


/* Helper function for edges() */
static void get_edge(GtsEdge *edge, GSList **edges)
{
  *edges = g_slist_prepend(*edges,edge);
}


static PyObject*
parent(PygtsSurface *self, PyObject *args)
{
  PyObject *e_;
  PygtsEdge *e;
  GtsFace *f;
  PygtsFace *face;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &e_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_edge_check(e_)) {
    PyErr_SetString(PyExc_TypeError,"expected an Edge");
    return NULL;
  }
  e = PYGTS_EDGE(e_);

  /* Make the call */
  if( (f=gts_edge_has_parent_surface(PYGTS_EDGE_AS_GTS_EDGE(e),
                             PYGTS_SURFACE_AS_GTS_SURFACE(self)))
      == NULL ) {
    Py_INCREF(Py_None);
    return Py_None;
  }

  if( (face = pygts_face_new(f)) == NULL ) {
    return NULL;
  }

  return (PyObject*)face;
}


static PyObject*
edges(PyObject *self, PyObject *args)
{
  PyObject *tuple=NULL, *obj;
  guint i,N;
  GSList *edges=NULL,*vertices=NULL,*e;
  PygtsEdge *edge;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "|O", &tuple) ) {
    return NULL;
  }

  if(tuple) {
    if(PyList_Check(tuple)) {
      tuple = PyList_AsTuple(tuple);
    }
    else {
      Py_INCREF(tuple);
    }
    if(!PyTuple_Check(tuple)) {
      Py_DECREF(tuple);
      PyErr_SetString(PyExc_TypeError,"expected a list or tuple of vertices");
      return NULL;
    }

    /* Assemble the GSList */
    N = PyTuple_Size(tuple);
    for(i=0;i<N;i++) {
      obj = PyTuple_GET_ITEM(tuple,i);
      if(!pygts_vertex_check(obj)) {
      Py_DECREF(tuple);
      g_slist_free(vertices);
      PyErr_SetString(PyExc_TypeError,"expected a list or tuple of vertices");
      return NULL;
      }
      vertices=g_slist_prepend(vertices,PYGTS_VERTEX_AS_GTS_VERTEX(obj));
    }
    Py_DECREF(tuple);

    /* Make the call */
    if( (edges = gts_edges_from_vertices(vertices,
                 PYGTS_SURFACE_AS_GTS_SURFACE(self))) == NULL ) {
      PyErr_SetString(PyExc_RuntimeError,"could not retrieve edges");
      return NULL;
    }
    g_slist_free(vertices);
  }
  else {
    /* Get all of the edges */
    gts_surface_foreach_edge(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)get_edge,&edges);
  }

  /* Assemble the return tuple */
  N = g_slist_length(edges);
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }
  e = edges;
  for(i=0;i<N;i++) {
    if( (edge = pygts_edge_new(GTS_EDGE(e->data))) == NULL ) {
      Py_DECREF(tuple);
      g_slist_free(edges);
      return NULL;
    }
    PyTuple_SET_ITEM(tuple,i,(PyObject*)edge);
    e = g_slist_next(e);
  }

  g_slist_free(edges);

  return tuple;
}


/* Helper function for edges() */
static void get_face(GtsFace *face, GSList **faces)
{
  *faces = g_slist_prepend(*faces,face);
}

static PyObject*
faces(PyObject *self, PyObject *args)
{
  PyObject *tuple=NULL, *obj;
  guint i,N;
  GSList *edges=NULL,*faces=NULL,*f;
  PygtsFace *face;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "|O", &tuple) ) {
    return NULL;
  }

  if(tuple) {
    if(PyList_Check(tuple)) {
      tuple = PyList_AsTuple(tuple);
    }
    else {
      Py_INCREF(tuple);
    }
    if(!PyTuple_Check(tuple)) {
      Py_DECREF(tuple);
      PyErr_SetString(PyExc_TypeError,"expected a list or tuple of edges");
      return NULL;
    }

    /* Assemble the GSList */
    N = PyTuple_Size(tuple);
    for(i=0;i<N;i++) {
      obj = PyTuple_GET_ITEM(tuple,i);
      if(!pygts_edge_check(obj)) {
      Py_DECREF(tuple);
      g_slist_free(edges);
      PyErr_SetString(PyExc_TypeError,"expected a list or tuple of edges");
      return NULL;
      }
      edges = g_slist_prepend(edges,PYGTS_EDGE_AS_GTS_EDGE(obj));
    }
    Py_DECREF(tuple);

  /* Make the call */
    if( (faces = gts_faces_from_edges(edges,PYGTS_SURFACE_AS_GTS_SURFACE(self)))
      == NULL ) {
      PyErr_SetString(PyExc_RuntimeError,"could not retrieve faces");
      return NULL;
    }
    g_slist_free(edges);
  }
  else {
    /* Get all of the edges */
    gts_surface_foreach_face(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)get_face,&faces);
  }

  /* Assemble the return tuple */
  N = g_slist_length(faces);
  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }

  f = faces;
  for(i=0;i<N;i++) {
    if( (face = pygts_face_new(GTS_FACE(f->data))) == NULL ) {
      Py_DECREF(tuple);
      g_slist_free(faces);
      return NULL;
    }
    PyTuple_SET_ITEM(tuple,i,(PyObject*)face);
    f = g_slist_next(f);
  }

  g_slist_free(faces);

  return tuple;
}


/* Helper for face_indices() */
00807 typedef struct {
  PyObject *vertices,*indices;  /* Vertex and indices tuples */
  guint Nv,Ni;                  /* Number of vertices and indices */
  guint n;                      /* Current face index */
  gboolean errflag;
} IndicesData;

/* Helper for face_indices() */
static void get_indices(GtsFace *face, IndicesData *data)
{
  PyObject *t;
  GtsVertex *v[3];
  guint i,j;
  gboolean flag;

  if(data->errflag) return;

  /* Put the vertex pointers in an array */
  gts_triangle_vertices( GTS_TRIANGLE(face), &(v[0]), &(v[1]), &(v[2]) );

  /* Create a tuple to put the indices into */
  if( (t=PyTuple_New(3)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    data->errflag = TRUE;
    return;
  }
  PyTuple_SET_ITEM(data->indices, data->n, t);

  /* Determine the indices */
  for(i=0;i<3;i++) {
    flag = FALSE;
    for(j=0;j<data->Nv;j++) {
      if( PYGTS_VERTEX_AS_GTS_VERTEX(PyTuple_GET_ITEM(data->vertices,j))
        ==v[i] ) {
      PyTuple_SET_ITEM(t, i, PyInt_FromLong(j));
      flag = TRUE;
      break;
      }
    }
    if(!flag) {
      PyErr_SetString(PyExc_RuntimeError,
                  "Could not initialize tuple (internal error)");
      data->errflag = TRUE;
      return;
    }
  }
  data->n += 1;
}


static PyObject*
face_indices(PygtsSurface *self, PyObject *args)
{
  PyObject *vertices,*indices;
  IndicesData data;
  guint Nv,Nf;
  guint i;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &vertices) )
    return NULL;

  /* Make sure that the tuple contains only vertices */
  Nv = PyTuple_Size(vertices);
  for(i=0;i<Nv;i++) {
    if(!pygts_vertex_check(PyTuple_GetItem(vertices,i))){
      PyErr_SetString(PyExc_TypeError,"Tuple has objects other than Vertices");
      return NULL;
    }
  }

  /* Get the number of faces in this surface */
  Nf = gts_surface_face_number(PYGTS_SURFACE_AS_GTS_SURFACE(self));

  /* Create a tuple to put the index tuples into */
  if( (indices=PyTuple_New(Nf)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }

  /* Initialize the IndicesData struct.  This is used to maintain state as each 
   * face is processed.
   */
  data.vertices = vertices;
  data.indices = indices;
  data.Nv = Nv;
  data.Ni = Nf;
  data.n = 0;
  data.errflag = FALSE;

  /* Process each face */
  gts_surface_foreach_face(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                     (GtsFunc)get_indices,&data);
  if(data.errflag) {
    Py_DECREF(data.indices);
    return NULL;
  }

  return indices;
}


static PyObject*
distance(PygtsSurface *self, PyObject *args)
{
  PyObject *s_;
  PygtsSurface *s;
  gdouble delta=0.1;
  GtsRange face_range, boundary_range;
  PyObject *fr, *br;

  SELF_CHECK

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O|d", &s_,&delta) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_surface_check(s_)) {
    PyErr_SetString(PyExc_TypeError,"expected a Surface");
    return NULL;
  }
  s = PYGTS_SURFACE(s_);

  gts_surface_distance(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                   PYGTS_SURFACE_AS_GTS_SURFACE(s),
                   delta, &face_range, &boundary_range);

  /* Populate the fr (face range) dict */
  if( (fr = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    return NULL;
  }
  PyDict_SetItemString(fr, "min", Py_BuildValue("d",face_range.min));
  PyDict_SetItemString(fr, "max", Py_BuildValue("d",face_range.max));
  PyDict_SetItemString(fr, "sum", Py_BuildValue("d",face_range.sum));
  PyDict_SetItemString(fr, "sum2", Py_BuildValue("d",face_range.sum2));
  PyDict_SetItemString(fr, "mean", Py_BuildValue("d",face_range.mean));
  PyDict_SetItemString(fr, "stddev", Py_BuildValue("d",face_range.stddev));
  PyDict_SetItemString(fr, "n", Py_BuildValue("i",face_range.n));

  /* Populate the br (boundary range) dict */
  if(gts_surface_boundary(PYGTS_SURFACE_AS_GTS_SURFACE(self))!=NULL) {
    if( (br = PyDict_New()) == NULL ) {
      PyErr_SetString(PyExc_MemoryError,"cannot create dict");
      Py_DECREF(fr);
      return NULL;
    }
    PyDict_SetItemString(br,"min",Py_BuildValue("d",boundary_range.min));
    PyDict_SetItemString(br,"max",Py_BuildValue("d",boundary_range.max));
    PyDict_SetItemString(br,"sum",Py_BuildValue("d",boundary_range.sum));
    PyDict_SetItemString(br,"sum2",Py_BuildValue("d",boundary_range.sum2));
    PyDict_SetItemString(br,"mean",Py_BuildValue("d",boundary_range.mean));
    PyDict_SetItemString(br,"stddev",Py_BuildValue("d",boundary_range.stddev));
    PyDict_SetItemString(br, "n",Py_BuildValue("i",boundary_range.n));

    return Py_BuildValue("OO",fr,br);
  }
  else {
    return Py_BuildValue("O",fr);
  }
}


static PyObject*
strip(PygtsSurface *self, PyObject *args)
{
  GSList *strips, *s, *f;
  PyObject *tuple, **tuples;
  guint i,j,n,N;
  PygtsFace *face=NULL;

  SELF_CHECK

  strips = gts_surface_strip(PYGTS_SURFACE_AS_GTS_SURFACE(self));
  
  /* Create tuples to put the Faces into */
  N = g_slist_length(strips);

  if( (tuple=PyTuple_New(N)) == NULL) {
    PyErr_SetString(PyExc_MemoryError,"could not create tuple");
    return NULL;
  }
  if( (tuples = (PyObject**)malloc(N*sizeof(PyObject*))) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"could not create array");
    Py_DECREF(tuple);
    return NULL;
  }
  s = strips;
  for(i=0;i<N;i++) {
    f = (GSList*)(s->data);
    n = g_slist_length(f);
    if( (tuples[i]=PyTuple_New(n)) == NULL) {
      PyErr_SetString(PyExc_MemoryError,"could not create tuple");
      Py_DECREF(tuple);
      free(tuples);
      return NULL;
    }
    PyTuple_SET_ITEM(tuple, i, tuples[i]);
    s = g_slist_next(s);
  }

  /* Put PygtsFace objects into the tuple */
  s = strips;
  for(i=0;i<N;i++) {
    f = (GSList*)(s->data);
    n = g_slist_length(f);
    for(j=0;j<n;j++) {
      if( (face = pygts_face_new(GTS_FACE(f->data))) == NULL ) {
      }
      PyTuple_SET_ITEM(tuples[i], j, (PyObject*)face);
      f = g_slist_next(f);
    }
    s = g_slist_next(s);
  }

  free(tuples);

  return tuple;
}


static PyObject*
stats(PygtsSurface *self, PyObject *args)
{
  GtsSurfaceStats stats;
  PyObject *dict, *edges_per_vertex, *faces_per_edge;

  SELF_CHECK

  /* Make the call */
  gts_surface_stats(PYGTS_SURFACE_AS_GTS_SURFACE(self),&stats);

  /* Create the dictionaries */
  if( (dict = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    return NULL;
  }
  if( (edges_per_vertex = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    return NULL;
  }
  if( (faces_per_edge = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    Py_DECREF(edges_per_vertex);
    return NULL;
  }

  /* Populate the edges_per_vertex dict */
  PyDict_SetItemString(edges_per_vertex,"min", 
                   Py_BuildValue("d",stats.edges_per_vertex.min));
  PyDict_SetItemString(edges_per_vertex,"max", 
                   Py_BuildValue("d",stats.edges_per_vertex.max));
  PyDict_SetItemString(edges_per_vertex,"sum", 
                   Py_BuildValue("d",stats.edges_per_vertex.sum));
  PyDict_SetItemString(edges_per_vertex,"sum2", 
                   Py_BuildValue("d",stats.edges_per_vertex.sum2));
  PyDict_SetItemString(edges_per_vertex,"mean", 
                   Py_BuildValue("d",stats.edges_per_vertex.mean));
  PyDict_SetItemString(edges_per_vertex,"stddev", 
                   Py_BuildValue("d",stats.edges_per_vertex.stddev));
  PyDict_SetItemString(edges_per_vertex,"n", 
                   Py_BuildValue("i",stats.edges_per_vertex.n));

  /* Populate the faces_per_edge dict */
  PyDict_SetItemString(faces_per_edge,"min", 
                   Py_BuildValue("d",stats.faces_per_edge.min));
  PyDict_SetItemString(faces_per_edge,"max", 
                   Py_BuildValue("d",stats.faces_per_edge.max));
  PyDict_SetItemString(faces_per_edge,"sum", 
                   Py_BuildValue("d",stats.faces_per_edge.sum));
  PyDict_SetItemString(faces_per_edge,"sum2", 
                   Py_BuildValue("d",stats.faces_per_edge.sum2));
  PyDict_SetItemString(faces_per_edge,"mean", 
                   Py_BuildValue("d",stats.faces_per_edge.mean));
  PyDict_SetItemString(faces_per_edge,"stddev", 
                   Py_BuildValue("d",stats.faces_per_edge.stddev));
  PyDict_SetItemString(faces_per_edge,"n", 
                   Py_BuildValue("i",stats.faces_per_edge.n));

  /* Populate the main dict */
  PyDict_SetItemString(dict,"n_faces", Py_BuildValue("i",stats.n_faces));
  PyDict_SetItemString(dict,"n_incompatible_faces", 
                   Py_BuildValue("i",stats.n_incompatible_faces));
  PyDict_SetItemString(dict,"n_boundary_edges", 
                   Py_BuildValue("i",stats.n_boundary_edges));
  PyDict_SetItemString(dict,"n_non_manifold_edges", 
                   Py_BuildValue("i",stats.n_non_manifold_edges));
  PyDict_SetItemString(dict,"edges_per_vertex", edges_per_vertex);
  PyDict_SetItemString(dict,"faces_per_edge", faces_per_edge);

  return dict;
}


static PyObject*
quality_stats(PygtsSurface *self, PyObject *args)
{
  GtsSurfaceQualityStats stats;
  PyObject *dict, *face_quality, *face_area, *edge_length, *edge_angle;

  SELF_CHECK

  /* Make the call */
  gts_surface_quality_stats(PYGTS_SURFACE_AS_GTS_SURFACE(self),&stats);

  /* Create the dictionaries */
  if( (dict = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    return NULL;
  }
  if( (face_quality = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    return NULL;
  }
  if( (face_area = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    Py_DECREF(face_quality);
    return NULL;
  }
  if( (edge_length = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    Py_DECREF(face_quality);
    Py_DECREF(face_area);
    return NULL;
  }
  if( (edge_angle = PyDict_New()) == NULL ) {
    PyErr_SetString(PyExc_MemoryError,"cannot create dict");
    Py_DECREF(dict);
    Py_DECREF(face_quality);
    Py_DECREF(face_area);
    Py_DECREF(edge_length);
    return NULL;
  }

  /* Populate the face_quality dict */
  PyDict_SetItemString(face_quality,"min", 
                   Py_BuildValue("d",stats.face_quality.min));
  PyDict_SetItemString(face_quality,"max", 
                   Py_BuildValue("d",stats.face_quality.max));
  PyDict_SetItemString(face_quality,"sum", 
                   Py_BuildValue("d",stats.face_quality.sum));
  PyDict_SetItemString(face_quality,"sum2", 
                   Py_BuildValue("d",stats.face_quality.sum2));
  PyDict_SetItemString(face_quality,"mean", 
                   Py_BuildValue("d",stats.face_quality.mean));
  PyDict_SetItemString(face_quality,"stddev", 
                   Py_BuildValue("d",stats.face_quality.stddev));
  PyDict_SetItemString(face_quality,"n", 
                   Py_BuildValue("i",stats.face_quality.n));

  /* Populate the face_area dict */
  PyDict_SetItemString(face_area,"min", 
                   Py_BuildValue("d",stats.face_area.min));
  PyDict_SetItemString(face_area,"max", 
                   Py_BuildValue("d",stats.face_area.max));
  PyDict_SetItemString(face_area,"sum", 
                   Py_BuildValue("d",stats.face_area.sum));
  PyDict_SetItemString(face_area,"sum2", 
                   Py_BuildValue("d",stats.face_area.sum2));
  PyDict_SetItemString(face_area,"mean", 
                   Py_BuildValue("d",stats.face_area.mean));
  PyDict_SetItemString(face_area,"stddev", 
                   Py_BuildValue("d",stats.face_area.stddev));
  PyDict_SetItemString(face_area,"n", 
                   Py_BuildValue("i",stats.face_area.n));

  /* Populate the edge_length dict */
  PyDict_SetItemString(edge_length,"min", 
                   Py_BuildValue("d",stats.edge_length.min));
  PyDict_SetItemString(edge_length,"max", 
                   Py_BuildValue("d",stats.edge_length.max));
  PyDict_SetItemString(edge_length,"sum", 
                   Py_BuildValue("d",stats.edge_length.sum));
  PyDict_SetItemString(edge_length,"sum2", 
                   Py_BuildValue("d",stats.edge_length.sum2));
  PyDict_SetItemString(edge_length,"mean", 
                   Py_BuildValue("d",stats.edge_length.mean));
  PyDict_SetItemString(edge_length,"stddev", 
                   Py_BuildValue("d",stats.edge_length.stddev));
  PyDict_SetItemString(edge_length,"n", 
                   Py_BuildValue("i",stats.edge_length.n));

  /* Populate the edge_angle dict */
  PyDict_SetItemString(edge_angle,"min", 
                   Py_BuildValue("d",stats.edge_angle.min));
  PyDict_SetItemString(edge_angle,"max", 
                   Py_BuildValue("d",stats.edge_angle.max));
  PyDict_SetItemString(edge_angle,"sum", 
                   Py_BuildValue("d",stats.edge_angle.sum));
  PyDict_SetItemString(edge_angle,"sum2", 
                   Py_BuildValue("d",stats.edge_angle.sum2));
  PyDict_SetItemString(edge_angle,"mean", 
                   Py_BuildValue("d",stats.edge_angle.mean));
  PyDict_SetItemString(edge_angle,"stddev", 
                   Py_BuildValue("d",stats.edge_angle.stddev));
  PyDict_SetItemString(edge_angle,"n", 
                   Py_BuildValue("i",stats.edge_angle.n));

  /* Populate the main dict */
  PyDict_SetItemString(dict,"face_quality", face_quality);
  PyDict_SetItemString(dict,"face_area", face_area);
  PyDict_SetItemString(dict,"edge_length", edge_length);
  PyDict_SetItemString(dict,"edge_angle", edge_angle);

  return dict;
}


static PyObject*
tessellate(PygtsSurface *self, PyObject *args)
{
  SELF_CHECK

  gts_surface_tessellate(PYGTS_SURFACE_AS_GTS_SURFACE(self),NULL,NULL);

  Py_INCREF(Py_None);
  return Py_None;
}


/* Helper function for inter() */
void
get_largest_coord(GtsVertex *v,gdouble *val) {
  if( fabs(GTS_POINT(v)->x) > *val ) *val = fabs(GTS_POINT(v)->x);
  if( fabs(GTS_POINT(v)->y) > *val ) *val = fabs(GTS_POINT(v)->y);
  if( fabs(GTS_POINT(v)->z) > *val ) *val = fabs(GTS_POINT(v)->z);
}

/* Helper function for intersection operations */
static PyObject*
inter(PygtsSurface *self, PyObject *args, GtsBooleanOperation op1,
      GtsBooleanOperation op2)
{
  PyObject *obj;
  PyObject *s_;
  PygtsSurface *s;
  GtsSurface *surface;
  GtsVector cm1, cm2;
  gdouble area1, area2;
  GtsSurfaceInter *si;
  GNode *tree1, *tree2;
  gboolean is_open1, is_open2, closed;
  gdouble eps=0.;

  /* Parse the args */  
  if(! PyArg_ParseTuple(args, "O", &s_) )
    return NULL;

  /* Convert to PygtsObjects */
  if(!pygts_surface_check(s_)) {
    PyErr_SetString(PyExc_TypeError,"expected a Surface");
    return NULL;
  }
  s = PYGTS_SURFACE(s_);

  /* Make sure that we don't have two pointers to the same surface */
  if( self == s ) {
      PyErr_SetString(PyExc_RuntimeError,
                  "can't determine intersection with self");
      return NULL;
  }


  /* *** ATTENTION ***
   * Eliminate any active gts traverse objects.  They appear to interfere
   * with the intersection calculation.  I would guess that this is due
   * to the use of the "reserved" field (i.e., it doesn't get properly
   * reset until the traverse is destroyed).
   *
   * I don't expect this to cause problems here, but a bug report should be
   * filed.
   */
  if(self->traverse!=NULL) {
    gts_surface_traverse_destroy(self->traverse);
    self->traverse = NULL;
  }
  if(s->traverse!=NULL) {
    gts_surface_traverse_destroy(s->traverse);
    s->traverse = NULL;
  }
  /* *** ATTENTION *** */

  /* Check for self-intersections in either surface */
  if( gts_surface_is_self_intersecting(PYGTS_SURFACE_AS_GTS_SURFACE(self))
      != NULL ) {
    PyErr_SetString(PyExc_RuntimeError,"Surface is self-intersecting");
    return NULL;
  }
  if( gts_surface_is_self_intersecting(PYGTS_SURFACE_AS_GTS_SURFACE(s))
      != NULL ) {
    PyErr_SetString(PyExc_RuntimeError,"Surface is self-intersecting");
    return NULL;
  }

  /* Avoid complete self-intersection of two surfaces*/
  if( (gts_surface_face_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)) ==
      gts_surface_face_number(PYGTS_SURFACE_AS_GTS_SURFACE(s))) &&
      (gts_surface_edge_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)) ==
       gts_surface_edge_number(PYGTS_SURFACE_AS_GTS_SURFACE(s))) &&
      (gts_surface_vertex_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)) ==
       gts_surface_vertex_number(PYGTS_SURFACE_AS_GTS_SURFACE(s))) &&
      (gts_surface_area(PYGTS_SURFACE_AS_GTS_SURFACE(self)) ==
       gts_surface_area(PYGTS_SURFACE_AS_GTS_SURFACE(s))) ) {

    area1 = \
      gts_surface_center_of_area(PYGTS_SURFACE_AS_GTS_SURFACE(self),cm1);

    area2 = \
      gts_surface_center_of_area(PYGTS_SURFACE_AS_GTS_SURFACE(s),cm2);

    if( (area1==area2) && (cm1[0]==cm2[0]) && (cm1[1]==cm2[1]) && 
      (cm1[2]==cm2[2]) ) {
      PyErr_SetString(PyExc_RuntimeError,"Surfaces mutually intersect");
      return NULL;
    }
  }

  /* Get bounding boxes */
  if( (tree1=gts_bb_tree_surface(PYGTS_SURFACE_AS_GTS_SURFACE(self)))
      ==NULL ) {
    PyErr_SetString(PyExc_MemoryError,"could not create tree");
    return NULL;
  }
  is_open1 = !gts_surface_is_closed(PYGTS_SURFACE_AS_GTS_SURFACE(self));
  if( (tree2=gts_bb_tree_surface(PYGTS_SURFACE_AS_GTS_SURFACE(s)))
      ==NULL ) {
    gts_bb_tree_destroy(tree1, TRUE);
    PyErr_SetString(PyExc_MemoryError,"could not create tree");
    return NULL;
  }
  is_open2 = !gts_surface_is_closed(PYGTS_SURFACE_AS_GTS_SURFACE(s));

  /* Get the surface intersection object */
  if( (si = gts_surface_inter_new(gts_surface_inter_class(),
                          PYGTS_SURFACE_AS_GTS_SURFACE(self),
                          PYGTS_SURFACE_AS_GTS_SURFACE(s),
                          tree1, tree2, is_open1, is_open2))==NULL) {
    gts_bb_tree_destroy(tree1, TRUE);
    gts_bb_tree_destroy(tree2, TRUE);
    PyErr_SetString(PyExc_RuntimeError,"could not create GtsSurfaceInter");
    return NULL;
  }
  gts_bb_tree_destroy(tree1, TRUE);
  gts_bb_tree_destroy(tree2, TRUE);

  /* Check that the surface intersection object is closed  */
  gts_surface_inter_check(si,&closed);
  if( closed == FALSE ) {
    gts_object_destroy(GTS_OBJECT(si));
    PyErr_SetString(PyExc_RuntimeError,"result is not closed");
    return NULL;
  }

  /* Create the surface */
  if( (surface = gts_surface_new(gts_surface_class(), gts_face_class(),
                         gts_edge_class(), gts_vertex_class()))
      == NULL )  {
    PyErr_SetString(PyExc_MemoryError, "could not create Surface");
    return NULL;
  }

  /* Calculate the new surface */
  gts_surface_inter_boolean(si, surface ,op1);
  gts_surface_inter_boolean(si, surface ,op2);
  gts_object_destroy(GTS_OBJECT(si));

  /* Clean up the result */
  gts_surface_foreach_vertex(surface, (GtsFunc)get_largest_coord, &eps);
  eps *= pow(2.,-50);
  pygts_vertex_cleanup(surface,1.e-9);
  pygts_edge_cleanup(surface);
  pygts_face_cleanup(surface);

  /* Check for self-intersection */
  if( gts_surface_is_self_intersecting(surface) != NULL ) {
    gts_object_destroy(GTS_OBJECT(surface));
    PyErr_SetString(PyExc_RuntimeError,"result is self-intersecting surface");
    return NULL;
  }

  /* Create the return Surface */
  if( (obj = (PyObject*)pygts_surface_new(surface)) == NULL ) {
    gts_object_destroy(GTS_OBJECT(surface));
    return NULL;
  }

  return obj;
}


static PyObject*
intersection(PygtsSurface *self, PyObject *args, GtsBooleanOperation op1,
           GtsBooleanOperation op2)
{
  SELF_CHECK
  return inter(self,args,GTS_1_IN_2,GTS_2_IN_1);
}


static PyObject*
pygts_union(PygtsSurface *self, PyObject *args)
{
  SELF_CHECK
  return inter(self,args,GTS_1_OUT_2,GTS_2_OUT_1);
}


static PyObject*
difference(PygtsSurface *self, PyObject *args)
{
  SELF_CHECK
  return inter(self,args,GTS_1_OUT_2,GTS_2_IN_1);
}


/* Helper for rotate(), scale() and translate() transforms */
01431 typedef struct {
  double dx, dy, dz, a;
  gboolean errflag;
} TransformData;

/* Helper for rotate() */
static void
rotate_point(GtsPoint *p, TransformData *data)
{
  if(data->errflag) return;

  if(pygts_point_rotate(p,data->dx,data->dy,data->dz,data->a)==-1)
    data->errflag=TRUE;
}

static PyObject*
rotate(PygtsSurface* self, PyObject *args, PyObject *keywds)
{
  TransformData data;
  static char *kwlist[] = {"dx", "dy", "dz", "a", NULL};

  SELF_CHECK

  data.dx=0; data.dy=0; data.dz=0; data.a=0;
  data.errflag = FALSE;

  /* Parse the args */
  if(! PyArg_ParseTupleAndKeywords(args, keywds,"|dddd", kwlist,
                           &(data.dx), &(data.dy), &(data.dz), 
                           &(data.a)) ) {
    return NULL;
  }

  gts_surface_foreach_vertex(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)rotate_point,&data);

  if(data.errflag) return NULL;

  Py_INCREF(Py_None);
  return Py_None;
}


/* Helper for scale() */
static void
scale_point(GtsPoint *p, TransformData *data)
{
  if(data->errflag) return;

  if(pygts_point_scale(p,data->dx,data->dy,data->dz)==-1)
    data->errflag=TRUE;
}

static PyObject*
scale(PygtsSurface* self, PyObject *args, PyObject *keywds)
{
  TransformData data;
  static char *kwlist[] = {"dx", "dy", "dz", NULL};

  SELF_CHECK

  data.dx=1; data.dy=1; data.dz=1; data.a=0;
  data.errflag = FALSE;

  /* Parse the args */
  if(! PyArg_ParseTupleAndKeywords(args, keywds,"|ddd", kwlist,
                           &(data.dx), &(data.dy), &(data.dz)) ) {
    return NULL;
  }

  gts_surface_foreach_vertex(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)scale_point,&data);

  if(data.errflag) return NULL;

  Py_INCREF(Py_None);
  return Py_None;
}


/* Helper for translate() */
static void
translate_point(GtsPoint *p, TransformData *data)
{
  if(data->errflag) return;

  if(pygts_point_translate(p,data->dx,data->dy,data->dz)==-1)
    data->errflag=TRUE;
}

static PyObject*
translate(PygtsSurface* self, PyObject *args, PyObject *keywds)
{
  TransformData data;
  static char *kwlist[] = {"dx", "dy", "dz", NULL};

  SELF_CHECK

  data.dx=0; data.dy=0; data.dz=0; data.a=0;
  data.errflag = FALSE;

  /* Parse the args */
  if(! PyArg_ParseTupleAndKeywords(args, keywds,"|ddd", kwlist,
                           &(data.dx), &(data.dy), &(data.dz)) ) {
    return NULL;
  }

  /* Make the call */
  gts_surface_foreach_vertex(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                       (GtsFunc)translate_point,&data);

  if(data.errflag) return NULL;

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
is_self_intersecting(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;
  gboolean ret = FALSE;

  SELF_CHECK

  if( (s=gts_surface_is_self_intersecting(PYGTS_SURFACE_AS_GTS_SURFACE(self)))
      != NULL) {
    gts_object_destroy(GTS_OBJECT(s));
    ret = TRUE;
  }

  if(ret) {
    Py_INCREF(Py_True);
    return Py_True;
  }
  else {
    Py_INCREF(Py_False);
    return Py_False;
  }  
}


static PyObject*
cleanup(PygtsSurface *self, PyObject *args)
{
  GtsSurface *s;
  gdouble threshold = 0.;

  SELF_CHECK

  /* Parse the args */
  if(! PyArg_ParseTuple(args,"|d", &threshold) ) {
    return NULL;
  }

  s = PYGTS_SURFACE_AS_GTS_SURFACE(self);

  /* Do the cleanup */
  if( threshold != 0. ) {
    pygts_vertex_cleanup(s,threshold);
  }
  pygts_edge_cleanup(s);
  pygts_face_cleanup(s);

  Py_INCREF(Py_None);
  return Py_None;
}


static PyObject*
coarsen(PygtsSurface *self, PyObject *args)
{
  guint n;
  gdouble amin=0.;
  GtsVolumeOptimizedParams params = {0.5,0.5,1.e-10};

  SELF_CHECK

  /* Parse the args */
  if(! PyArg_ParseTuple(args,"i|d", &n, &amin) ) {
    return NULL;
  }

  /* Make the call */
  gts_surface_coarsen(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                  (GtsKeyFunc)gts_volume_optimized_cost, &params,
                  (GtsCoarsenFunc)gts_volume_optimized_vertex, &params,
                  (GtsStopFunc)gts_coarsen_stop_number, &n, amin);

  Py_INCREF(Py_None);
  return Py_None;
}


/* Methods table */
static PyMethodDef methods[] = {
  {"is_ok", (PyCFunction)is_ok,
   METH_NOARGS,
   "True if this Surface s is OK.  False otherwise.\n"
   "\n"
   "Signature: s.is_ok()\n"
  },

  {"add", (PyCFunction)add,
   METH_VARARGS,
   "Adds a Face f or Surface s2 to Surface s1.\n"
   "\n"
   "Signature: s1.add(f) or s2.add(f)\n"
  },

  {"remove", (PyCFunction)pygts_remove,
   METH_VARARGS,
   "Removes Face f from this Surface s.\n"
   "\n"
   "Signature: s.remove(f)\n"
  },

  {"copy", (PyCFunction)copy,
   METH_VARARGS,
   "Copys all Faces, Edges and Vertices of Surface s2 to Surface s1.\n"
   "\n"
   "Signature: s1.copy(s2)\n"
   "\n"
   "Returns s1.\n"
  },

  {"is_manifold", (PyCFunction)is_manifold,
   METH_NOARGS,
   "True if Surface s is a manifold, False otherwise.\n"
   "\n"
   "Signature: s.is_manifold()\n"
  },

  {"manifold_faces", (PyCFunction)manifold_faces,
   METH_VARARGS,
   "Returns the 2 manifold Faces of Edge e on this Surface s\n"
   "if they exist, or None.\n"
   "\n"
   "Signature: s.manifold_faces(e)\n"
  },

  {"is_orientable", (PyCFunction)is_orientable,
   METH_NOARGS,
   "True if Faces in Surface s have compatible orientation,\n"
   "False otherwise.\n"
   "Note that a closed surface is also a manifold.  Note that an\n"
   "orientable surface is also a manifold.\n"
   "\n"
   "Signature: s.is_orientable()\n"
  },

  {"is_closed", (PyCFunction)is_closed,
   METH_NOARGS,
   "True if Surface s is closed, False otherwise.\n"
   "Note that a closed Surface is also a manifold.\n"
   "\n"
   "Signature: s.is_closed()\n"
  },

  {"boundary", (PyCFunction)boundary,
   METH_NOARGS,
   "Returns a tuple of boundary Edges of Surface s.\n"
   "\n"
   "Signature: s.boundary()\n"
  },

  {"area", (PyCFunction)area,
   METH_NOARGS,
   "Returns the area of Surface s.\n"
   "The area is taken as the sum of the signed areas of the Faces of s.\n"
   "\n"
   "Signature: s.area()\n"
  },

  {"volume", (PyCFunction)volume,
   METH_NOARGS,
   "Returns the signed volume of the domain bounded by the Surface s.\n"
   "\n"
   "Signature: s.volume()\n"
  },

  {"center_of_mass", (PyCFunction)center_of_mass,
   METH_NOARGS,
   "Returns the coordinates of the center of mass of Surface s.\n"
   "\n"
   "Signature: s.center_of_mass()\n"
  },

  {"center_of_area", (PyCFunction)center_of_area,
   METH_NOARGS,
   "Returns the coordinates of the center of area of Surface s.\n"
   "\n"
   "Signature: s.center_of_area()\n"
  },

  {"write", (PyCFunction)pygts_write,
   METH_VARARGS,
   "Saves Surface s to File f in GTS ascii format.\n"
   "All the lines beginning with #! are ignored.\n"
   "\n"
   "Signature: s.write(f)\n"
  },

  {"write_oogl", (PyCFunction)pygts_write_oogl,
   METH_VARARGS,
   "Saves Surface s to File f in OOGL (Geomview) format.\n"
   "\n"
   "Signature: s.write_oogl(f)\n"
  },

  {"write_oogl_boundary", (PyCFunction)pygts_write_oogl_boundary,
   METH_VARARGS,
   "Saves boundary of Surface s to File f in OOGL (Geomview) format.\n"
   "\n"
   "Signature: s.write_oogl_boundary(f)\n"
  },

  {"write_vtk", (PyCFunction)pygts_write_vtk,
   METH_VARARGS,
   "Saves Surface s to File f in VTK format.\n"
   "\n"
   "Signature: s.write_vtk(f)\n"
  },

  {"fan_oriented", (PyCFunction)fan_oriented,
   METH_VARARGS,
   "Returns a tuple of outside Edges of the Faces fanning from\n"
   "Vertex v on this Surface s.  The Edges are given in \n"
   "counter-clockwise order.\n"
   "\n"
   "Signature: s.fan_oriented(v)\n"
  },

  {"split", (PyCFunction)split,
   METH_NOARGS,
   "Splits a surface into a tuple of connected and manifold components.\n"
   "\n"
   "Signature: s.split()\n"
  },

  {"distance", (PyCFunction)distance,
   METH_VARARGS,
   "Calculates the distance between the faces of this Surface s1 and\n"
   "the nearest Faces of other s2, and (if applicable) the distance\n"
   "between the boundary of this Surface s1 and the nearest boundary\n"
   "Edges of other s2.\n"
   "\n"
   "One or two dictionaries are returned (where applicable), the first\n"
   "for the face range and the second for the boundary range.  The\n"
   "fields in each dictionary describe statistical results for each\n"
   "population: {min,max,sum,sum2,mean,stddev,n}.\n"
   "\n"
   "Signature: s1.distance(s2) or s1.distance(s2,delta)\n"
   "\n"
   "The value delta is a spatial increment defined as the percentage\n"
   "of the diagonal of the bounding box of s2 (default 0.1).\n"
  },

  {"strip", (PyCFunction)strip,
   METH_NOARGS,
   "Returns a tuple of strips, where each strip is a tuple of Faces\n"
   "that are successive and have one edge in common.\n"
   "\n"
   "Signature: s.split()\n"
  },

  {"stats", (PyCFunction)stats,
   METH_NOARGS,
   "Returns statistics for this Surface f in a dict.\n"
   "The stats include n_faces, n_incompatible_faces,, n_boundary_edges,\n"
   "n_non_manifold_edges, and the statisics {min, max, sum, sum2, mean,\n"
   "stddev, and n} for populations of edges_per_vertex and\n"
   "faces_per_edge.  Each of these names are dictionary keys.\n"
   "\n"
   "Signature: s.stats()\n"
  },

  {"quality_stats", (PyCFunction)quality_stats,
   METH_NOARGS,
   "Returns quality statistics for this Surface f in a dict.\n"
   "The statistics include the {min, max, sum, sum2, mean, stddev,\n"
   "and n} for populations of face_quality, face_area, edge_length,\n"
   "and edge_angle.  Each of these names are dictionary keys.\n"
   "See Triangle.quality() for an explanation of the face_quality.\n"
   "\n"
   "Signature: s.quality_stats()\n"
  },

  {"tessellate", (PyCFunction)tessellate,
   METH_NOARGS,
   "Tessellate each face of this Surface s with 4 triangles.\n"
   "The number of triangles is increased by a factor of 4.\n"
   "\n"
   "Signature: s.tessellate()\n"
  },

  {"vertices", (PyCFunction)vertices,
   METH_NOARGS,
   "Returns a tuple containing the vertices of Surface s.\n"
   "\n"
   "Signature: s.vertices()\n"
  },

  {"parent", (PyCFunction)parent,
   METH_VARARGS,
   "Returns Face on this Surface s that has Edge e, or None\n"
   "if the Edge is not on this Surface.\n"
   "\n"
   "Signature: s.parent(e)\n"
  },

  {"edges", (PyCFunction)edges,
   METH_VARARGS,
   "Returns tuple of Edges on Surface s that have Vertex in list.\n"
   "If a list is not given then all of the Edges are returned.\n"
   "\n"
   "Signature: s.edges(list) or s.edges()\n"
  },

  {"faces", (PyCFunction)faces,
   METH_VARARGS,
   "Returns tuple of Faces on Surface s that have Edge in list.\n"
   "If a list is not given then all of the Faces are returned.\n"
   "\n"
   "Signature: s.faces(list) s.faces()\n"
  },

  {"face_indices", (PyCFunction)face_indices,
   METH_VARARGS,
   "Returns a tuple of 3-tuples containing Vertex indices for each Face\n"
   "in Surface s.  The index for each Vertex in a face corresponds to\n"
   "where it is found in the Vertex tuple vs.\n"
   "\n"
   "Signature: s.face_indices(vs)\n"
  },

  {"intersection", (PyCFunction)intersection,
   METH_VARARGS,
   "Returns the intersection of this Surface s1 with Surface s2.\n"
   "\n"
   "Signature: s1.intersection(s2)\n"
  },

  {"union", (PyCFunction)pygts_union,
   METH_VARARGS,
   "Returns the union of this Surface s1 with Surface s2.\n"
   "\n"
   "Signature: s1.union(s2)\n"
  },

  {"difference", (PyCFunction)difference,
   METH_VARARGS,
   "Returns the difference of this Surface s1 with Surface s2.\n"
   "\n"
   "Signature: s1.difference(s2)\n"
  },

  {"rotate", (PyCFunction)rotate,
   METH_VARARGS | METH_KEYWORDS,
   "Rotates Surface s about vector dx,dy,dz and angle a.\n"
   "The sense of the rotation is given by the right-hand-rule.\n"
   "\n"
   "Signature: s.rotate(dx,dy,dz,a)\n"
  },

  {"scale", (PyCFunction)scale,
   METH_VARARGS | METH_KEYWORDS,
   "Scales Surface s by vector dx,dy,dz.\n"
   "\n"
   "Signature: s.scale(dx=1,dy=1,dz=1)\n"
  },

  {"translate", (PyCFunction)translate,
   METH_VARARGS | METH_KEYWORDS,
   "Translates Surface s by vector dx,dy,dz.\n"
   "\n"
   "Signature: s.translate(dx=0,dy=0,dz=0)\n"
  },

  {"is_self_intersecting", (PyCFunction)is_self_intersecting,
   METH_NOARGS,
   "Returns True if this Surface s is self-intersecting.\n"
   "False otherwise.\n"
   "\n"
   "Signature: s.is_self_intersecting()\n"
  },

  {"cleanup", (PyCFunction)cleanup,
   METH_VARARGS,
   "Cleans up the Vertices, Edges, and Faces on a Surface s.\n"
   "\n"
   "Signature: s.cleanup() or s.cleanup(threhold)\n"
   "\n"
   "If threhold is given, then Vertices that are spaced less than\n"
   "the threshold are merged.  Degenerate Edges and Faces are also\n"
   "removed.\n"
  },

  {"coarsen", (PyCFunction)coarsen,
   METH_VARARGS,
   "Reduces the number of vertices on Surface s.\n"
   "\n"
   "Signature: s.coarsen(n) and s.coarsen(amin)\n"
   "\n"
   "n is the smallest number of desired edges (but you may get fewer).\n"
   "amin is the smallest angle between Faces.\n"
  },

  {NULL}  /* Sentinel */
};


/*-------------------------------------------------------------------------*/
/* Attributes exported to python */

static PyObject *
get_Nvertices(PygtsSurface *self, void *closure)
{
  SELF_CHECK
  return Py_BuildValue("i",
      gts_surface_vertex_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)));

}


static PyObject *
get_Nedges(PygtsSurface *self, void *closure)
{
  SELF_CHECK
  return Py_BuildValue("i",
      gts_surface_edge_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)));
}


static PyObject *
get_Nfaces(PygtsSurface *self, void *closure)
{
  SELF_CHECK
  return Py_BuildValue("i",
      gts_surface_face_number(PYGTS_SURFACE_AS_GTS_SURFACE(self)));
}

/* Methods table */
static PyGetSetDef getset[] = {
  { "Nvertices", (getter)get_Nvertices, NULL, 
    "The number of unique vertices", NULL
  },

  { "Nedges", (getter)get_Nedges, NULL, 
    "The number of unique edges", NULL
  },

  { "Nfaces", (getter)get_Nfaces, NULL, 
    "The number of unique faces", NULL
  },

  {NULL}  /* Sentinel */
};


/*-------------------------------------------------------------------------*/
/* Python type methods */

static void
dealloc(PygtsSurface* self)
{
  if(self->traverse!=NULL) {
    gts_surface_traverse_destroy(self->traverse);
  }
  self->traverse = NULL;

  /* Chain up */
  PygtsObjectType.tp_dealloc((PyObject*)self);
}


static PyObject *
new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
  PyObject *o;
  PygtsObject *obj;
  guint alloc_gtsobj = TRUE;

  /* Parse the args */
  if(kwds) {
    o = PyDict_GetItemString(kwds,"alloc_gtsobj");
    if(o==Py_False) {
      alloc_gtsobj = FALSE;
    }
    if(o!=NULL) {
      PyDict_DelItemString(kwds, "alloc_gtsobj");
    }
  }
  if(kwds) {
    Py_INCREF(Py_False);
    PyDict_SetItemString(kwds,"alloc_gtsobj", Py_False);
  }

  /* Chain up */
  obj = PYGTS_OBJECT(PygtsObjectType.tp_new(type,args,kwds));

  PYGTS_SURFACE(obj)->traverse = NULL;

  /* Allocate the gtsobj (if needed) */
  if( alloc_gtsobj ) {
    obj->gtsobj = GTS_OBJECT(gts_surface_new(gts_surface_class(),
                                   gts_face_class(),
                                   gts_edge_class(),
                                   gts_vertex_class()));

    if( obj->gtsobj == NULL )  {
      PyErr_SetString(PyExc_MemoryError, "could not create Surface");
      return NULL;
    }

    pygts_object_register(obj);
  }

  return (PyObject*)obj;
}


static int
init(PygtsSurface *self, PyObject *args, PyObject *kwds)
{
  gint ret;

  if( (ret = PygtsObjectType.tp_init((PyObject*)self,args,kwds)) != 0 ) {
    return ret;
  }

  return 0;
}


/* Helper function for iter */
static void 
get_f0(GtsFace *f,GtsFace **f0)
{
  if(*f0==NULL) *f0 = f;
}

PyObject* 
iter(PygtsSurface *self)
{
  GtsFace* f0=NULL;

  SELF_CHECK

  if(self->traverse!=NULL) {
    gts_surface_traverse_destroy(self->traverse);
    self->traverse = NULL;
  }

  /* Assign a "first" face */
  gts_surface_foreach_face(PYGTS_SURFACE_AS_GTS_SURFACE(self),
                     (GtsFunc)get_f0,&f0);
  if(f0==NULL) {
    PyErr_SetString(PyExc_RuntimeError, "No faces to traverse");
    return NULL;
  }

  if( (self->traverse=gts_surface_traverse_new(
           PYGTS_SURFACE_AS_GTS_SURFACE(self),f0)) == NULL ) {
    PyErr_SetString(PyExc_MemoryError, "could not create Traverse");
    return NULL;
  }

  Py_INCREF((PyObject*)self);
  return (PyObject*)self;
}


PyObject* 
iternext(PygtsSurface *self)
{
  PygtsFace *face;
  GtsFace *f;

  SELF_CHECK

  if( self->traverse == NULL ) {
    PyErr_SetString(PyExc_RuntimeError, "iterator not initialized");
    return NULL;
  }

  /* Get the next face */
  if( (f = gts_surface_traverse_next(self->traverse,NULL)) == NULL ) {
    gts_surface_traverse_destroy(self->traverse);
    self->traverse = NULL;
    PyErr_SetString(PyExc_StopIteration, "No more faces");
    return NULL;
  }

  if( (face = pygts_face_new(f)) == NULL ) {
    return NULL;
  }

  return (PyObject*)face;
}


/* Methods table */
PyTypeObject PygtsSurfaceType = {
    PyObject_HEAD_INIT(NULL)
    0,                       /* ob_size */
    "gts.Surface",           /* tp_name */
    sizeof(PygtsSurface),    /* tp_basicsize */
    0,                       /* tp_itemsize */
    (destructor)dealloc,     /* tp_dealloc */
    0,                       /* tp_print */
    0,                       /* tp_getattr */
    0,                       /* tp_setattr */
    0,                       /* tp_compare */
    0,                       /* tp_repr */
    0,                       /* tp_as_number */
    0,                       /* tp_as_sequence */
    0,                       /* tp_as_mapping */
    0,                       /* tp_hash */
    0,                       /* tp_call */
    0,                       /* tp_str */
    0,                       /* tp_getattro */
    0,                       /* tp_setattro */
    0,                       /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT |
      Py_TPFLAGS_BASETYPE |
      Py_TPFLAGS_HAVE_ITER,  /* tp_flags */
    "Surface object",        /* tp_doc */
    0,                       /* tp_traverse */
    0,                       /* tp_clear */
    0,                       /* tp_richcompare */
    0,                       /* tp_weaklistoffset */
    (getiterfunc)iter,       /* tp_iter */
    (iternextfunc)iternext,  /* tp_iternext */
    methods,                 /* tp_methods */
    0,                       /* tp_members */
    getset,                  /* tp_getset */
    0,                       /* tp_base */
    0,                       /* tp_dict */
    0,                       /* tp_descr_get */
    0,                       /* tp_descr_set */
    0,                       /* tp_dictoffset */
    (initproc)init,          /* tp_init */
    0,                       /* tp_alloc */
    (newfunc)new             /* tp_new */
};


/*-------------------------------------------------------------------------*/
/* Pygts functions */

gboolean 
pygts_surface_check(PyObject* o)
{
  if(! PyObject_TypeCheck(o, &PygtsSurfaceType)) {
    return FALSE;
  }
  else {
#if PYGTS_DEBUG
    return pygts_surface_is_ok(PYGTS_SURFACE(o));
#else
    return TRUE;
#endif
  }
}


/* Helper function */
static void 
face_is_ok(GtsFace *f,gboolean *ret)
{
  if( !pygts_gts_triangle_is_ok(GTS_TRIANGLE(f)) ) {
    *ret = FALSE;
  }
}


gboolean 
pygts_surface_is_ok(PygtsSurface *s)
{
  PygtsObject *obj;
  gboolean ret=TRUE;

  obj = PYGTS_OBJECT(s);

  if(!pygts_object_is_ok(PYGTS_OBJECT(s))) return FALSE;
  g_return_val_if_fail(obj->gtsobj_parent==NULL,FALSE);

  /* Check all of the faces this surface contains */
  gts_surface_foreach_face(GTS_SURFACE(obj->gtsobj),(GtsFunc)face_is_ok,&ret);
  if( ret == FALSE ) return FALSE;

  return TRUE;
}


PygtsSurface *
pygts_surface_new(GtsSurface *s) {
  PyObject *args, *kwds;
  PygtsObject *surface;

  /* Check for Surface in the object table */
  if( (surface = PYGTS_OBJECT(g_hash_table_lookup(obj_table,GTS_OBJECT(s)))) 
      !=NULL ) {
    Py_INCREF(surface);
    return PYGTS_SURFACE(surface);
  }

  /* Build a new Surface */
  args = Py_BuildValue("()");
  kwds = Py_BuildValue("{s:O}","alloc_gtsobj",Py_False);
  surface = PYGTS_OBJECT(PygtsSurfaceType.tp_new(&PygtsSurfaceType,args,kwds));
  Py_DECREF(args);
  Py_DECREF(kwds);
  if( surface == NULL ) {
    PyErr_SetString(PyExc_MemoryError, "could not create Surface");
    return NULL;
  }
  surface->gtsobj = GTS_OBJECT(s);

  /* Register and return */
  pygts_object_register(surface);
  return PYGTS_SURFACE(surface);
}

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