Method IntersectPolygonWithPolygon

Common/DataModel/vtkPolygon.cxx:2090–2164

------------------------------------------------------------------------------ Method intersects two polygons. You must supply the number of points and point coordinates (npts, *pts) and the bounding box (bounds) of the two polygons. Also supply a tolerance squared for controlling error. The method returns 1 if there is an intersection, and 0 if not. A single point of intersection x[3] is also ret

// not. A single point of intersection x[3] is also returned if there
// is an intersection.
int vtkPolygon::IntersectPolygonWithPolygon(int npts, double* pts, double bounds[6], int npts2,
  double* pts2, double bounds2[6], double tol2, double x[3])
{
  double n[3], coords[3];
  int i, j;
  double *p1, *p2, ray[3];
  double t;

  //  Intersect each edge of first polygon against second
  //
  vtkPolygon::ComputeNormal(npts2, pts2, n);

  for (i = 0; i < npts; i++)
  {
    p1 = pts + 3 * i;
    p2 = pts + 3 * ((i + 1) % npts);

    for (j = 0; j < 3; j++)
    {
      ray[j] = p2[j] - p1[j];
    }
    if (!vtkBox::IntersectBox(bounds2, p1, ray, coords, t))
    {
      continue;
    }

    if ((vtkPlane::IntersectWithLine(p1, p2, n, pts2, t, x)) == 1)
    {
      if ((npts2 == 3 && vtkTriangle::PointInTriangle(x, pts2, pts2 + 3, pts2 + 6, tol2)) ||
        (npts2 > 3 && vtkPolygon::PointInPolygon(x, npts2, pts2, bounds2, n) == VTK_POLYGON_INSIDE))
      {
        return 1;
      }
    }
    else
    {
      return 0;
    }
  }

  //  Intersect each edge of second polygon against first
  //
  vtkPolygon::ComputeNormal(npts, pts, n);

  for (i = 0; i < npts2; i++)
  {
    p1 = pts2 + 3 * i;
    p2 = pts2 + 3 * ((i + 1) % npts2);

    for (j = 0; j < 3; j++)
    {
      ray[j] = p2[j] - p1[j];
    }

    if (!vtkBox::IntersectBox(bounds, p1, ray, coords, t))
    {
      continue;
    }