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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkTriangle.h,v $
  Language:  C++
  Date:      $Date: 2001/11/30 19:14:14 $
  Version:   $Revision: 1.74 $


Copyright (c) 1993-2001 Ken Martin, Will Schroeder, Bill Lorensen 
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

 * Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

 * Neither name of Ken Martin, Will Schroeder, or Bill Lorensen nor the names
   of any contributors may be used to endorse or promote products derived
   from this software without specific prior written permission.

 * Modified source versions must be plainly marked as such, and must not be
   misrepresented as being the original software.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

=========================================================================*/
// .NAME vtkTriangle - a cell that represents a triangle
// .SECTION Description
// vtkTriangle is a concrete implementation of vtkCell to represent a triangle
// located in 3-space.

#ifndef __vtkTriangle_h
#define __vtkTriangle_h

#include "vtkCell.h"
#include "vtkMath.h"
#include "vtkLine.h"
#include "vtkQuadric.h"

class VTK_COMMON_EXPORT vtkTriangle : public vtkCell
{
public:
  static vtkTriangle *New();
  vtkTypeMacro(vtkTriangle,vtkCell);

  // Description:
  // Create a new cell and copy this triangle's information into the
  // cell. Returns a pointer to the new cell created.
  vtkCell *MakeObject();

  // Description:
  // Get the edge specified by edgeId (range 0 to 2) and return that edge's
  // coordinates.
  vtkCell *GetEdge(int edgeId);

  // Description:
  // See the vtkCell API for descriptions of these methods.
  int GetCellType() {return VTK_TRIANGLE;};
  int GetCellDimension() {return 2;};
  int GetNumberOfEdges() {return 3;};
  int GetNumberOfFaces() {return 0;};
  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);
  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 Triangulate(int index, vtkIdList *ptIds, vtkPoints *pts);
  void Derivatives(int subId, float pcoords[3], float *values, 
                   int dim, float *derivs);

  // Description:
  // Clip this triangle using scalar value provided. Like contouring, except
  // that it cuts the triangle to produce other triangles.
  void Clip(float value, vtkDataArray *cellScalars, 
            vtkPointLocator *locator, vtkCellArray *polys,
            vtkPointData *inPd, vtkPointData *outPd,
            vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd,
            int insideOut);

  // Description:
  // Plane intersection plus in/out test on triangle. The in/out test is 
  // performed using tol as the tolerance.
  int IntersectWithLine(float p1[3], float p2[3], float tol, float& t,
                        float x[3], float pcoords[3], int& subId);

  // Description:
  // Return the center of the triangle in parametric coordinates.
  int GetParametricCenter(float pcoords[3]);

  // Description:
  // Compute the center of the triangle.
  static void TriangleCenter(float p1[3], float p2[3], float p3[3], 
                             float center[3]);

  // Description:
  // Compute the area of a triangle in 3D.
  static float TriangleArea(float p1[3], float p2[3], float p3[3]);
  
  // Description:
  // Compute the circumcenter (center[3]) and radius (method return value) of
  // a triangle defined by the three points x1, x2, and x3. (Note that the
  // coordinates are 2D. 3D points can be used but the z-component will be
  // ignored.)
  static double Circumcircle(double  p1[2], double p2[2], double p3[2], 
                            double center[2]);

  // Description:
  // Given a 2D point x[2], determine the barycentric coordinates of the point.
  // Barycentric coordinates are a natural coordinate system for simplices that
  // express a position as a linear combination of the vertices. For a 
  // triangle, there are three barycentric coordinates (because there are
  // three vertices), and the sum of the coordinates must equal 1. If a 
  // point x is inside a simplex, then all three coordinates will be strictly 
  // positive.  If two coordinates are zero (so the third =1), then the 
  // point x is on a vertex. If one coordinates are zero, the point x is on an 
  // edge. In this method, you must specify the vertex coordinates x1->x3. 
  // Returns 0 if triangle is degenerate.
  static int BarycentricCoords(double x[2], double  x1[2], double x2[2], 
                               double x3[2], double bcoords[3]);
  
  
  // Description:
  // Project triangle defined in 3D to 2D coordinates. Returns 0 if
  // degenerate triangle; non-zero value otherwise. Input points are x1->x3;
  // output 2D points are v1->v3.
  static int ProjectTo2D(double x1[3], double x2[3], double x3[3],
                         double v1[2], double v2[2], double v3[2]);

  // Description:
  // Compute the triangle normal from a points list, and a list of point ids
  // that index into the points list.
  static void ComputeNormal(vtkPoints *p, int numPts, vtkIdType *pts,
                            float n[3]);

  // Description:
  // Compute the triangle normal from three points.
  static void ComputeNormal(float v1[3], float v2[3], float v3[3], float n[3]);

  // Description:
  // Compute the (unnormalized) triangle normal direction from three points.
  static void ComputeNormalDirection(float v1[3], float v2[3], float v3[3],
                                     float n[3]);
  
  // Description:
  // Compute the triangle normal from three points (double-precision version).
  static void ComputeNormal(double v1[3], double v2[3], double v3[3], 
                            double n[3]);
  
  // Description:
  // Compute the (unnormalized) triangle normal direction from three points
  // (double precision version).
  static void ComputeNormalDirection(double v1[3], double v2[3], double v3[3],
                                     double n[3]);

  // Description:
  // Given a point x, determine whether it is inside (within the
  // tolerance squared, tol2) the triangle defined by the three 
  // coordinate values p1, p2, p3. Method is via comparing dot products.
  // (Note: in current implementation the tolerance only works in the
  // neighborhood of the three vertices of the triangle.
  static int PointInTriangle(float x[3], float x1[3], float x2[3], float x3[3], 
                             float tol2);

  // Description:
  // Calculate the error quadric for this triangle.  Return the
  // quadric as a 4x4 matrix or a vtkQuadric.  (from Peter
  // Lindstrom's Siggraph 2000 paper, "Out-of-Core Simplification of
  // Large Polygonal Models")
  static void ComputeQuadric(float x1[3], float x2[3], float x3[3],
                             float quadric[4][4]);
  static void ComputeQuadric(float x1[3], float x2[3], float x3[3],
                             vtkQuadric *quadric);
  

protected:
  vtkTriangle();
  ~vtkTriangle();

  vtkLine *Line;

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

inline int vtkTriangle::GetParametricCenter(float pcoords[3])
{
  pcoords[0] = pcoords[1] = 0.333; pcoords[2] = 0.0;
  return 0;
}

inline void vtkTriangle::ComputeNormalDirection(float v1[3], float v2[3], 
                                       float v3[3], float n[3])
{
  float ax, ay, az, bx, by, bz;

  // order is important!!! maintain consistency with triangle vertex order 
  ax = v3[0] - v2[0]; ay = v3[1] - v2[1]; az = v3[2] - v2[2];
  bx = v1[0] - v2[0]; by = v1[1] - v2[1]; bz = v1[2] - v2[2];

  n[0] = (ay * bz - az * by);
  n[1] = (az * bx - ax * bz);
  n[2] = (ax * by - ay * bx);
}

inline void vtkTriangle::ComputeNormal(float v1[3], float v2[3], 
                                       float v3[3], float n[3])
{
  float length;
  
  vtkTriangle::ComputeNormalDirection(v1, v2, v3, n);
  
  if ( (length = sqrt((n[0]*n[0] + n[1]*n[1] + n[2]*n[2]))) != 0.0 )
    {
    n[0] /= length;
    n[1] /= length;
    n[2] /= length;
    }
}

inline void vtkTriangle::ComputeNormalDirection(double v1[3], double v2[3], 
                                       double v3[3], double n[3])
{
  double ax, ay, az, bx, by, bz;

  // order is important!!! maintain consistency with triangle vertex order 
  ax = v3[0] - v2[0]; ay = v3[1] - v2[1]; az = v3[2] - v2[2];
  bx = v1[0] - v2[0]; by = v1[1] - v2[1]; bz = v1[2] - v2[2];

  n[0] = (ay * bz - az * by);
  n[1] = (az * bx - ax * bz);
  n[2] = (ax * by - ay * bx);
}

inline void vtkTriangle::ComputeNormal(double v1[3], double v2[3], 
                                       double v3[3], double n[3])
{
  double length;

  vtkTriangle::ComputeNormalDirection(v1, v2, v3, n);

  if ( (length = sqrt((n[0]*n[0] + n[1]*n[1] + n[2]*n[2]))) != 0.0 )
    {
    n[0] /= length;
    n[1] /= length;
    n[2] /= length;
    }
}

inline void vtkTriangle::TriangleCenter(float p1[3], float p2[3], float p3[3],
                                       float center[3])
{
  center[0] = (p1[0]+p2[0]+p3[0]) / 3.0;
  center[1] = (p1[1]+p2[1]+p3[1]) / 3.0;
  center[2] = (p1[2]+p2[2]+p3[2]) / 3.0;
}

inline float vtkTriangle::TriangleArea(float p1[3], float p2[3], float p3[3])
{
  float a,b,c;
  a = vtkMath::Distance2BetweenPoints(p1,p2);
  b = vtkMath::Distance2BetweenPoints(p2,p3);
  c = vtkMath::Distance2BetweenPoints(p3,p1);
  return (0.25* sqrt(fabs((double)4.0*a*c - (a-b+c)*(a-b+c))));
} 

#endif


