/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkPolygon.h
  Language:  C++
  Date:      $Date$
  Version:   $Revision$

  Copyright (c) 1993-2002 Ken Martin, Will Schroeder, Bill Lorensen 
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
// .NAME vtkPolygon - a cell that represents an n-sided polygon
// .SECTION Description
// vtkPolygon is a concrete implementation of vtkCell to represent a 2D 
// n-sided polygon. The polygons cannot have any internal holes, and cannot
// self-intersect. Define the polygon with n-points ordered in the clockwise
// direction; do not repeat the last point.

#ifndef __vtkPolygon_h
#define __vtkPolygon_h

#include "vtkCell.h"

class vtkFloatArray;
class vtkLine;
class vtkPoints;
class vtkQuad;
class vtkTriangle;

class VTK_COMMON_EXPORT vtkPolygon : public vtkCell
{
public:
  static vtkPolygon *New();
  vtkTypeRevisionMacro(vtkPolygon,vtkCell);

  // Description:
  // See the vtkCell API for descriptions of these methods.
  int GetCellType() {return VTK_POLYGON;};
  int GetCellDimension() {return 2;};
  int GetNumberOfEdges() {return this->GetNumberOfPoints();};
  int GetNumberOfFaces() {return 0;};
  vtkCell *GetEdge(int edgeId);
  vtkCell *GetFace(int) {return 0;};
  int CellBoundary(int subId, float pcoords[3], vtkIdList *pts);
  void Contour(float value, vtkDataArray *cellScalars, 
               vtkPointLocator *locator,vtkCellArray *verts, 
               vtkCellArray *lines, vtkCellArray *polys,
               vtkPointData *inPd, vtkPointData *outPd,
               vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd);
  void Clip(float value, vtkDataArray *cellScalars, 
            vtkPointLocator *locator, vtkCellArray *tris,
            vtkPointData *inPd, vtkPointData *outPd,
            vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd,
            int insideOut);
  int EvaluatePosition(float x[3], float* closestPoint,
                       int& subId, float pcoords[3],
                       float& dist2, float *weights);
  void EvaluateLocation(int& subId, float pcoords[3], float x[3],
                        float *weights);
  int IntersectWithLine(float p1[3], float p2[3], float tol, float& t,
                        float x[3], float pcoords[3], int& subId);
  int Triangulate(int index, vtkIdList *ptIds, vtkPoints *pts);
  void Derivatives(int subId, float pcoords[3], float *values, 
                   int dim, float *derivs);

  // Description:
  // Polygon specific methods.
  static void ComputeNormal(vtkPoints *p, int numPts, vtkIdType *pts,
                            float n[3]);
  static void ComputeNormal(vtkPoints *p, float n[3]);
  
  // Description:
  // Compute the polygon normal from an array of points. This version assumes
  // that the polygon is convex, and looks for the first valid normal.
  static void ComputeNormal(int numPts, float *pts, float n[3]);

  // Description:
  // Compute interpolation weights using 1/r**2 normalized sum.
  void ComputeWeights(float x[3], float *weights);


  // Description:
  // Create a local s-t coordinate system for a polygon. The point p0 is
  // the origin of the local system, p10 is s-axis vector, and p20 is the 
  // t-axis vector. (These are expressed in the modeling coordinate system and
  // are vectors of dimension [3].) The values l20 and l20 are the lengths of
  // the vectors p10 and p20, and n is the polygon normal.
  int ParameterizePolygon(float p0[3], float p10[3], float &l10, 
                          float p20[3], float &l20, float n[3]);
  
  // Description:
  // Determine whether point is inside polygon. Function uses ray-casting
  // to determine if point is inside polygon. Works for arbitrary polygon shape
  // (e.g., non-convex). Returns 0 if point is not in polygon; 1 if it is.
  // Can also return -1 to indicate degenerate polygon.
  static int PointInPolygon(float x[3], int numPts, float *pts, 
                            float bounds[6], float n[3]);  

  // Description:
  // Triangulate this polygon. The user must provide the vtkIdList outTris.
  // On output, the outTris list contains the ids of the points defining 
  // the triangulation. The ids are ordered into groups of three: each 
  // three-group defines one triangle.
  int Triangulate(vtkIdList *outTris);
  
  // Description:
  // Method intersects two polygons. You must supply the number of points and
  // point coordinates (npts, *pts) and the bounding box (bounds) of the two
  // polygons. Also supply a tolerance squared for controlling
  // error. The method returns 1 if there is an intersection, and 0 if
  // not. A single point of intersection x[3] is also returned if there
  // is an intersection.
  static int IntersectPolygonWithPolygon(int npts, float *pts, float bounds[6],
                                         int npts2, float *pts2, 
                                         float bounds2[3], float tol,
                                         float x[3]);

protected:
  vtkPolygon();
  ~vtkPolygon();

  // variables used by instances of this class
  float   Tolerance; // Intersection tolerance
  int     SuccessfulTriangulation; // Stops recursive tri. if necessary
  float   Normal[3]; //polygon normal
  vtkIdList *Tris;
  vtkTriangle *Triangle;
  vtkQuad *Quad;
  vtkFloatArray *TriScalars;
  vtkLine *Line;

  // Helper methods for triangulation------------------------------
  // Description: 
  // A fast triangulation method. Uses recursive divide and 
  // conquer based on plane splitting  to reduce loop into triangles.  
  // The cell (e.g., triangle) is presumed properly initialized (i.e., 
  // Points and PointIds).
  int EarCutTriangulation();

private:
  vtkPolygon(const vtkPolygon&);  // Not implemented.
  void operator=(const vtkPolygon&);  // Not implemented.
};

#endif

