Method PolygonIntersectsBBox

Common/DataModel/vtkPlanesIntersection.cxx:282–401

//

int vtkPlanesIntersection::PolygonIntersectsBBox(double bounds[6], vtkPoints* pts)
{
  // a bogus vtkPlanesIntersection object containing only one plane

  vtkPlanesIntersection* pi = vtkPlanesIntersection::New();

  pi->SetRegionVertices(pts);

  vtkPoints* Box = vtkPoints::New();
  Box->SetNumberOfPoints(8);
  Box->SetPoint(0, bounds[0], bounds[2], bounds[4]);
  Box->SetPoint(1, bounds[1], bounds[2], bounds[4]);
  Box->SetPoint(2, bounds[1], bounds[3], bounds[4]);
  Box->SetPoint(3, bounds[0], bounds[3], bounds[4]);
  Box->SetPoint(4, bounds[0], bounds[2], bounds[5]);
  Box->SetPoint(5, bounds[1], bounds[2], bounds[5]);
  Box->SetPoint(6, bounds[1], bounds[3], bounds[5]);
  Box->SetPoint(7, bounds[0], bounds[3], bounds[5]);

  int intersects = -1;

  //  1.  Does Box intersect the polygon's bounding box?

  if (pi->IntersectsBoundingBox(Box) == 0)
  {
    intersects = 0;
  }

  //  2.  If so, does Box entirely contain the polygon's bounding box?

  else if (pi->EnclosesBoundingBox(Box) == 1)
  {
    intersects = 1;
  }

  if (intersects == -1)
  {

    //  3. If not, determine whether the Box intersects the plane of the polygon

    vtkPoints* origin = vtkPoints::New();
    origin->SetNumberOfPoints(1);
    origin->SetPoint(0, pts->GetPoint(0));

    vtkFloatArray* normal = vtkFloatArray::New();
    normal->SetNumberOfComponents(3);
    normal->SetNumberOfTuples(1);

    // find 3 points that are not co-linear and compute a normal

    double nvec[3], p0[3], p1[3], pp[3];

    int npts = pts->GetNumberOfPoints();

    pts->GetPoint(0, p0);
    pts->GetPoint(1, p1);

    for (int p = 2; p < npts; p++)