Method FindBoundaryEdge

Rendering/Annotation/vtkCubeAxesActor.cxx:2384–2502

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void vtkCubeAxesActor::FindBoundaryEdge(int& xloc, int& yloc, int& zloc, double pts[8][3])
{
  // boundary edges fly mode
  xloc = yloc = zloc = 1;
  int i, xIdx = 0, yIdx = 0, zIdx = 0, zIdx2 = 0;
  int xAxes = 0, yAxes = 0, zAxes = 0;
  double slope = 0.0, minSlope, num, den, d2;
  double e1[3], e2[3], e3[3];
  int idx = 0;

  // Find distance to origin
  double d2Min = VTK_FLOAT_MAX;
  for (i = 0; i < 8; i++)
  {
    d2 = pts[i][0] * pts[i][0] + pts[i][1] * pts[i][1];
    if (d2 < d2Min)
    {
      d2Min = d2;
      idx = i;
    }
  }

  // find minimum slope point connected to closest point and on
  // right side (in projected coordinates). This is the first edge.
  minSlope = VTK_FLOAT_MAX;
  for (xIdx = 0, i = 0; i < 3; i++)
  {
    num = (pts[vtkCubeAxesActorConn[idx][i]][1] - pts[idx][1]);
    den = (pts[vtkCubeAxesActorConn[idx][i]][0] - pts[idx][0]);
    if (den != 0.0)
    {
      slope = num / den;
    }
    if (slope < minSlope && den > 0)
    {
      xIdx = vtkCubeAxesActorConn[idx][i];
      yIdx = vtkCubeAxesActorConn[idx][(i + 1) % 3];
      zIdx = vtkCubeAxesActorConn[idx][(i + 2) % 3];
      xAxes = i;
      minSlope = slope;
    }
  }

  // find edge (connected to closest point) on opposite side
  for (i = 0; i < 3; i++)
  {
    e1[i] = (pts[xIdx][i] - pts[idx][i]);
    e2[i] = (pts[yIdx][i] - pts[idx][i]);
    e3[i] = (pts[zIdx][i] - pts[idx][i]);
  }
  vtkMath::Normalize(e1);
  vtkMath::Normalize(e2);
  vtkMath::Normalize(e3);

  if (vtkMath::Dot(e1, e2) < vtkMath::Dot(e1, e3))
  {
    yAxes = (xAxes + 1) % 3;
  }