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

  Program:   Visualization Toolkit
  Module:    vtkTriangle.cc
  Language:  C++
  Date:      $Date$
  Version:   $Revision$


Copyright (c) 1993-1996 Ken Martin, Will Schroeder, Bill Lorensen.

This software is copyrighted by Ken Martin, Will Schroeder and Bill Lorensen.
The following terms apply to all files associated with the software unless
explicitly disclaimed in individual files. This copyright specifically does
not apply to the related textbook "The Visualization Toolkit" ISBN
013199837-4 published by Prentice Hall which is covered by its own copyright.

The authors hereby grant permission to use, copy, and distribute this
software and its documentation for any purpose, provided that existing
copyright notices are retained in all copies and that this notice is included
verbatim in any distributions. Additionally, the authors grant permission to
modify this software and its documentation for any purpose, provided that
such modifications are not distributed without the explicit consent of the
authors and that existing copyright notices are retained in all copies. Some
of the algorithms implemented by this software are patented, observe all
applicable patent law.

IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
OF THE USE OF THIS SOFTWARE, ITS DOCUMENTATION, OR ANY DERIVATIVES THEREOF,
EVEN IF THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES, INCLUDING,
BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE, AND NON-INFRINGEMENT.  THIS SOFTWARE IS PROVIDED ON AN
"AS IS" BASIS, AND THE AUTHORS AND DISTRIBUTORS HAVE NO OBLIGATION TO PROVIDE
MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.


=========================================================================*/
#include "vtkTriangle.hh"
#include "vtkPolygon.hh"
#include "vtkPlane.hh"
#include "vtkMath.hh"
#include "vtkCellArray.hh"
#include "vtkLine.hh"
#include "vtkPointLocator.hh"

static vtkPolygon poly;
static vtkPlane plane;

// Description:
// Deep copy of cell.
vtkTriangle::vtkTriangle(const vtkTriangle& t)
{
  this->Points = t.Points;
  this->PointIds = t.PointIds;
}

int vtkTriangle::EvaluatePosition(float x[3], float closestPoint[3],
                                 int& subId, float pcoords[3], 
                                 float& dist2, float *weights)
{
  int i, j;
  float *pt1, *pt2, *pt3, n[3];
  float rhs[2], c1[2], c2[2];
  float det;
  float maxComponent;
  int idx=0, indices[2];

  subId = 0;
  pcoords[0] = pcoords[1] = pcoords[2] = 0.0;
//
// Get normal for triangle
//
  pt1 = this->Points.GetPoint(1);
  pt2 = this->Points.GetPoint(2);
  pt3 = this->Points.GetPoint(0);

  poly.ComputeNormal (pt1, pt2, pt3, n);
//
// Project point to plane
//
  plane.ProjectPoint(x,pt1,n,closestPoint);
//
// Construct matrices.  Since we have over determined system, need to find
// which 2 out of 3 equations to use to develop equations. (Any 2 should 
// work since we've projected point to plane.)
//
  for (maxComponent=0.0, i=0; i<3; i++)
    {
    if (fabs(n[i]) > maxComponent)
      {
      maxComponent = fabs(n[i]);
      idx = i;
      }
    }
  for (j=0, i=0; i<3; i++)  
    {
    if ( i != idx ) indices[j++] = i;
    }
  
  for (i=0; i<2; i++)
    {  
    rhs[i] = closestPoint[indices[i]] - pt3[indices[i]];
    c1[i] = pt1[indices[i]] - pt3[indices[i]];
    c2[i] = pt2[indices[i]] - pt3[indices[i]];
    }

  if ( (det = vtkMath::Determinant2x2(c1,c2)) == 0.0 ) return -1;

  pcoords[0] = vtkMath::Determinant2x2 (rhs,c2) / det;
  pcoords[1] = vtkMath::Determinant2x2 (c1,rhs) / det;
  pcoords[2] = 1.0 - pcoords[0] - pcoords[1];
//
// Okay, now find closest point to element
//
  weights[0] = pcoords[2];
  weights[1] = pcoords[0];
  weights[2] = pcoords[1];

  if ( pcoords[0] >= 0.0 && pcoords[0] <= 1.0 &&
  pcoords[1] >= 0.0 && pcoords[1] <= 1.0 &&
  pcoords[2] >= 0.0 && pcoords[2] <= 1.0 )
    {
    dist2 = vtkMath::Distance2BetweenPoints(closestPoint,x); //projection distance
    return 1;
    }
  else
    {
    static vtkLine line;
    float t;

    if ( pcoords[0] < 0.0 && pcoords[1] < 0.0 )
      {
      dist2 = vtkMath::Distance2BetweenPoints(x,pt3);
      for (i=0; i<3; i++) closestPoint[i] = pt3[i];
      }
    else if ( pcoords[1] < 0.0 && pcoords[2] < 0.0 )
      {
      dist2 = vtkMath::Distance2BetweenPoints(x,pt1);
      for (i=0; i<3; i++) closestPoint[i] = pt1[i];
      }
    else if ( pcoords[0] < 0.0 && pcoords[2] < 0.0 )
      {
      dist2 = vtkMath::Distance2BetweenPoints(x,pt2);
      for (i=0; i<3; i++) closestPoint[i] = pt2[i];
      }
    else if ( pcoords[0] < 0.0 )
      {
      dist2 = line.DistanceToLine(x,pt2,pt3,t,closestPoint);
      }
    else if ( pcoords[1] < 0.0 )
      {
      dist2 = line.DistanceToLine(x,pt1,pt3,t,closestPoint);
      }
    else if ( pcoords[2] < 0.0 )
      {
      dist2 = line.DistanceToLine(x,pt1,pt2,t,closestPoint);
      }
    return 0;
    }
}

void vtkTriangle::EvaluateLocation(int& vtkNotUsed(subId), float pcoords[3],
				   float x[3], float *weights)
{
  float u3;
  float *pt0, *pt1, *pt2;
  int i;

  pt0 = this->Points.GetPoint(0);
  pt1 = this->Points.GetPoint(1);
  pt2 = this->Points.GetPoint(2);

  u3 = 1.0 - pcoords[0] - pcoords[1];

  for (i=0; i<3; i++)
    {
    x[i] = pt0[i]*u3 + pt1[i]*pcoords[0] + pt2[i]*pcoords[1];
    }

  weights[0] = u3;
  weights[1] = pcoords[0];
  weights[2] = pcoords[1];
}

int vtkTriangle::CellBoundary(int vtkNotUsed(subId), float pcoords[3],
			      vtkIdList& pts)
{
  float t1=pcoords[0]-pcoords[1];
  float t2=0.5*(1.0-pcoords[0])-pcoords[1];
  float t3=2.0*pcoords[0]+pcoords[1]-1.0;

  pts.Reset();

  // compare against three lines in parametric space that divide element
  // into three pieces
  if ( t1 >= 0.0 && t2 >= 0.0 )
    {
    pts.SetId(0,this->PointIds.GetId(0));
    pts.SetId(1,this->PointIds.GetId(1));
    }

  else if ( t2 < 0.0 && t3 >= 0.0 )
    {
    pts.SetId(0,this->PointIds.GetId(1));
    pts.SetId(1,this->PointIds.GetId(2));
    }

  else //( t1 < 0.0 && t3 < 0.0 )
    {
    pts.SetId(0,this->PointIds.GetId(2));
    pts.SetId(1,this->PointIds.GetId(0));
    }

  if ( pcoords[0] < 0.0 || pcoords[1] < 0.0 ||
  pcoords[0] > 1.0 || pcoords[1] > 1.0 || (1.0 - pcoords[0] - pcoords[1]) < 0.0 )
    return 0;
  else
    return 1;

}

//
// Marching triangles
//
typedef int EDGE_LIST;
typedef struct {
       EDGE_LIST edges[3];
} LINE_CASES;

static LINE_CASES lineCases[] = { 
  {{-1, -1, -1}},
  {{0, 2, -1}},
  {{1, 0, -1}},
  {{1, 2, -1}},
  {{2, 1, -1}},
  {{0, 1, -1}},
  {{2, 0, -1}},
  {{-1, -1, -1}}
};

void vtkTriangle::Contour(float value, vtkFloatScalars *cellScalars, 
			  vtkPointLocator *locator,
			  vtkCellArray *vtkNotUsed(verts), 
			  vtkCellArray *lines, 
			  vtkCellArray *vtkNotUsed(polys), 
			  vtkFloatScalars *scalars)
{
  static int CASE_MASK[3] = {1,2,4};
  LINE_CASES *lineCase;
  EDGE_LIST  *edge;
  int i, j, index, *vert;
  static int edges[3][2] = { {0,1}, {1,2}, {2,0} };
  int pts[2];
  float t, *x1, *x2, x[3];

  // Build the case table
  for ( i=0, index = 0; i < 3; i++)
      if (cellScalars->GetScalar(i) >= value)
          index |= CASE_MASK[i];

  lineCase = lineCases + index;
  edge = lineCase->edges;

  for ( ; edge[0] > -1; edge += 2 )
    {
    for (i=0; i<2; i++) // insert line
      {
      vert = edges[edge[i]];
      t = (value - cellScalars->GetScalar(vert[0])) /
          (cellScalars->GetScalar(vert[1]) - cellScalars->GetScalar(vert[0]));
      x1 = this->Points.GetPoint(vert[0]);
      x2 = this->Points.GetPoint(vert[1]);
      for (j=0; j<3; j++) x[j] = x1[j] + t * (x2[j] - x1[j]);
      if ( (pts[i] = locator->IsInsertedPoint(x)) < 0 )
        {
        pts[i] = locator->InsertNextPoint(x);
        scalars->InsertScalar(pts[i],value);
        }
      }
    lines->InsertNextCell(2,pts);
    }
}

vtkCell *vtkTriangle::GetEdge(int edgeId)
{
  static vtkLine line;
  int edgeIdPlus1 = edgeId + 1;

  if (edgeIdPlus1 > 2) edgeIdPlus1 = 0;

  // load point id's
  line.PointIds.SetId(0,this->PointIds.GetId(edgeId));
  line.PointIds.SetId(1,this->PointIds.GetId(edgeIdPlus1));

  // load coordinates
  line.Points.SetPoint(0,this->Points.GetPoint(edgeId));
  line.Points.SetPoint(1,this->Points.GetPoint(edgeIdPlus1));

  return &line;
}

//
// Plane intersection plus in/out test on triangle.
//
int vtkTriangle::IntersectWithLine(float p1[3], float p2[3], float tol, 
                                  float& t, float x[3], float pcoords[3], 
                                  int& subId)
{
  float *pt1, *pt2, *pt3, n[3];
  float tol2 = tol*tol;
  float closestPoint[3];
  float dist2, weights[3];

  subId = 0;
  pcoords[0] = pcoords[1] = pcoords[2] = 0.0;
//
// Get normal for triangle
//
  pt1 = this->Points.GetPoint(1);
  pt2 = this->Points.GetPoint(2);
  pt3 = this->Points.GetPoint(0);

  poly.ComputeNormal (pt1, pt2, pt3, n);
//
// Intersect plane of triangle with line
//
  if ( ! plane.IntersectWithLine(p1,p2,n,pt1,t,x) ) return 0;
//
// Evaluate position
//
  if (this->EvaluatePosition(x, closestPoint, subId, pcoords, dist2, weights)
      >= 0)
    {
    if ( dist2 <= tol2 ) return 1;
    }
  
  return 0;
}

int vtkTriangle::Triangulate(int vtkNotUsed(index), vtkFloatPoints &pts)
{
  pts.Reset();
  pts.InsertPoint(0,this->Points.GetPoint(0));
  pts.InsertPoint(1,this->Points.GetPoint(1));
  pts.InsertPoint(2,this->Points.GetPoint(2));

  return 1;
}

// Used a staged computation: first compute derivatives in local x'-y' coordinate 
// system; then convert into x-y-z modelling system.
void vtkTriangle::Derivatives(int vtkNotUsed(subId), float vtkNotUsed(pcoords)[3], 
                              float *values, int dim, float *derivs)
{
  float v0[2], v1[2], v2[2], v[3], v10[3], v20[3], lenX;
  float *x0, *x1, *x2, n[3];
  double *J[2], J0[2], J1[2];
  double *JI[2], JI0[2], JI1[2];
  float functionDerivs[6], sum[2], dBydx, dBydy;
  int i, j;

  // Project points of triangle into 2D system
  x0 = this->Points.GetPoint(0);
  x1 = this->Points.GetPoint(1);
  x2 = this->Points.GetPoint(2);
  poly.ComputeNormal (x0, x1, x2, n);

  for (i=0; i < 3; i++) 
    {
    v10[i] = x1[i] - x0[i];
    v[i] = x2[i] - x0[i];
    }

  vtkMath::Cross(n,v10,v20); //creates local y' axis

  if ( (lenX=vtkMath::Normalize(v10)) <= 0.0 || vtkMath::Normalize(v20) <= 0.0 ) //degenerate
    {
    for ( j=0; j < dim; j++ )
      for ( i=0; i < 3; i++ )
        derivs[j*dim + i] = 0.0;
    return;
    }

  v0[0] = v0[1] = 0.0; //convert points to 2D (i.e., local system)
  v1[0] = lenX; v1[1] = 0.0;
  v2[0] = vtkMath::Dot(v,v10);
  v2[1] = vtkMath::Dot(v,v20);

  // Compute interpolation function derivatives
  functionDerivs[0] = -1; //r derivatives
  functionDerivs[1] = 1;
  functionDerivs[2] = 0;
  functionDerivs[3] = -1; //s derivatives
  functionDerivs[4] = 0;
  functionDerivs[5] = 1;

  // Compute Jacobian: Jacobian is constant for a triangle.
  J[0] = J0; J[1] = J1;
  JI[0] = JI0; JI[1] = JI1;

  J[0][0] = v1[0] - v0[0];
  J[1][0] = v2[0] - v0[0];
  J[0][1] = v1[1] - v0[1];
  J[1][1] = v2[1] - v0[1];

  // Compute inverse Jacobian
  vtkMath::InvertMatrix(J,JI,2);

  // Loop over "dim" derivative values. For each set of values, compute derivatives
  // in local system and then transform into modelling system.
  // First compute derivatives in local x'-y' coordinate system
  for ( j=0; j < dim; j++ )
    {
    sum[0] = sum[1] = 0.0;
    for ( i=0; i < 3; i++) //loop over interp. function derivatives
      {
      sum[0] += functionDerivs[i] * values[dim*i + j]; 
      sum[1] += functionDerivs[3 + i] * values[dim*i + j];
      }
    dBydx = sum[0]*JI[0][0] + sum[1]*JI[0][1];
    dBydy = sum[0]*JI[1][0] + sum[1]*JI[1][1];

    // Transform into global system (dot product with global axes)
    derivs[3*j] = dBydx * v10[0] + dBydy * v20[0];
    derivs[3*j + 1] = dBydx * v10[1] + dBydy * v20[1];
    derivs[3*j + 2] = dBydx * v10[2] + dBydy * v20[2];
    }
}

// Special dot product definition for 2-vectors
#define VTK_DOT(_x,_y) _x[0]*_y[0] + _x[1]*_y[1]

// 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.)
float vtkTriangle::Circumcircle(float  x1[2], float x2[2], float x3[2], 
                                float center[2])
{
  double n12[2], n13[2], x12[2], x13[2];
  double *A[2], rhs[2], sum, diff;
  int i;
//
//  calculate normals and intersection points of bisecting planes.  
//
  for (i=0; i<2; i++) 
    {
    n12[i] = x2[i] - x1[i];
    n13[i] = x3[i] - x1[i];
    x12[i] = (x2[i] + x1[i])/2.0;
    x13[i] = (x3[i] + x1[i])/2.0;
    }
//
//  Compute solutions to the intersection of two bisecting lines
//  (2-eqns. in 2-unknowns).
//
//  form system matrices
//
  A[0] = n12;
  A[1] = n13;

  rhs[0] = VTK_DOT(n12,x12);
  rhs[1] = VTK_DOT(n13,x13);
//
// Solve system of equations
//
  if ( vtkMath::SolveLinearSystem(A,rhs,2) == 0 )
    {
    center[0] = center[1] = 0.0;
    return VTK_LARGE_FLOAT;
    }
  else
    {
    center[0] = rhs[0]; center[1] = rhs[1];
    }

  //determine average value of radius squared
  for (sum=0, i=0; i<2; i++) 
    {
    diff = x1[i] - center[i];
    sum += diff*diff;
    diff = x2[i] - center[i];
    sum += diff*diff;
    diff = x3[i] - center[i];
    sum += diff*diff;
    }

  if ( (sum /= 3.0) > VTK_LARGE_FLOAT ) return VTK_LARGE_FLOAT;
  else return sum;
}
#undef VTK_DOT

// 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
// fourthree 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.
int vtkTriangle::BarycentricCoords(float x[2], float  x1[2], float x2[2], 
                                   float x3[2], float bcoords[3])
{
  double *A[3], p[3], a1[3], a2[3], a3[3];
  int i;

  //
  // Homogenize the variables; load into arrays.
  //
  a1[0] = x1[0]; a1[1] = x2[0]; a1[2] = x3[0]; 
  a2[0] = x1[1]; a2[1] = x2[1]; a2[2] = x3[1]; 
  a3[0] = 1.0;   a3[1] = 1.0;   a3[2] = 1.0;   
  p[0] = x[0]; p[1] = x[1]; p[2] = x[2];

  //
  //   Now solve system of equations for barycentric coordinates
  //
  A[0] = a1;
  A[1] = a2;
  A[2] = a3;

  if ( vtkMath::SolveLinearSystem(A,p,3) )
    {
    for (i=0; i<3; i++) bcoords[i] = (float) p[i];
    return 1;
    }
  else
    {
    return 0;
    }
}

// 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.
int vtkTriangle::ProjectTo2D(float x1[3], float x2[3], float x3[3],
                             float v1[2], float v2[2], float v3[2])
{
  float n[3], v21[3], v31[3], v[3], xLen;

  // Get normal for triangle
  poly.ComputeNormal (x1, x2, x3, n);

  for (int i=0; i < 3; i++) 
    {
    v21[i] = x2[i] - x1[i];
    v31[i] = x3[i] - x1[i];
    }

  if ( (xLen=vtkMath::Normalize(v21)) <= 0.0 ) return 0;

  // The first point is at (0,0); the next at (xLen,0); compute the other point relative 
  // to the first two.
  v1[0] = v1[1] = 0.0;
  v2[0] = xLen; v2[1] = 0.0;

  vtkMath::Cross(n,v21,v);

  v3[0] = vtkMath::Dot(v31,v21);
  v3[1] = vtkMath::Dot(v31,v);

  return 1;
}
