Method ComputeNormal

Filters/Texture/vtkTextureMapToPlane.cxx:214–294

#define VTK_TOLERANCE 1.0e-03

void vtkTextureMapToPlane::ComputeNormal(vtkDataSet* output)
{
  vtkIdType numPts = output->GetNumberOfPoints();
  double m[9], v[3], x[3];
  vtkIdType ptId;
  int dir = 0, i;
  double length, w, *c1, *c2, *c3, det;

  //  First thing to do is to get an initial normal and point to define
  //  the plane.  Then, use this information to construct better
  //  matrices.  If problem occurs, then the point and plane becomes the
  //  fallback value.
  //
  //  Get minimum width of bounding box.
  const double* bounds = output->GetBounds();
  length = output->GetLength();

  for (w = length, i = 0; i < 3; i++)
  {
    this->Normal[i] = 0.0;
    if ((bounds[2 * i + 1] - bounds[2 * i]) < w)
    {
      dir = i;
      w = bounds[2 * i + 1] - bounds[2 * i];
    }
  }

  //  If the bounds is perpendicular to one of the axes, then can
  //  quickly compute normal.
  //
  this->Normal[dir] = 1.0;
  if (w <= (length * VTK_TOLERANCE))
  {
    return;
  }

  //  Need to compute least squares approximation.  Depending on major
  //  normal direction (dir), construct matrices appropriately.
  //
  //  Compute 3x3 least squares matrix
  v[0] = v[1] = v[2] = 0.0;
  for (i = 0; i < 9; i++)
  {
    m[i] = 0.0;
  }

  for (ptId = 0; ptId < numPts; ptId++)
  {
    output->GetPoint(ptId, x);

    v[0] += x[0] * x[2];
    v[1] += x[1] * x[2];
    v[2] += x[2];

    m[0] += x[0] * x[0];
    m[1] += x[0] * x[1];
    m[2] += x[0];