[vtkusers] VTK render coordinates

[Toepfer, Randall]

I have a mesh in vtk.  I created a function to convert the mesh to point
cloud library pcl::PointCloud.

int vtk2pcl(vtkPolyData* poly_data, pcl::PointCloud<pcl::PointXYZ>::Ptr&
pcl_cloud)
{
  pcl_cloud->clear();

  vtkSmartPointer<vtkPoints> mesh_points = poly_data->GetPoints();
  vtkIdType nr_points = mesh_points->GetNumberOfPoints();
  if (nr_points == 0)
    return 0;

  pcl_cloud->points.resize(nr_points);
  double point_xyz[3];
  for (vtkIdType i = 0; i < mesh_points->GetNumberOfPoints(); ++i)
  {
    mesh_points->GetPoint(i, &point_xyz[0]);
    pcl_cloud->points[i].x = static_cast<float>(point_xyz[0]);
    pcl_cloud->points[i].y = static_cast<float>(point_xyz[1]);
    pcl_cloud->points[i].z = static_cast<float>(point_xyz[2]);
  }
  pcl_cloud->width = static_cast<uint32_t>(pcl_cloud->points.size());
  pcl_cloud->height = 1;
  pcl_cloud->is_dense = true;

  return (static_cast<int>(nr_points));
}

I then use this point cloud in PCL's segmentation methods to find planes in
my mesh.

If I compare the bounds and centroid of my mesh to my point cloud - both
are equal.

I display the planes in VTK:

auto A = plane[0];
auto B = plane[1];
auto C = plane[2];
auto D = plane[3];
double z = (-1 * D) / (-1 * ((A * min_x) + (B * 1)) * C);
plane_source->SetCenter(min_x, 1, z);
z = (-1 * D) / (-1 * ((A * min_x) + (B * max_y)) * C);
plane_source->SetPoint1(min_x, max_y, z);
z = (-1 * D) / (-1 * ((A * max_x) + (B * max_y)) * C);
plane_source->SetPoint2(max_x, max_y, z);

plane_source->Update();

vtkPolyData* vtk_plane = plane_source->GetOutput();
// Create a mapper and actor
vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputData(vtk_plane);
vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
actor->SetMapper(mapper);


I display the mesh in VTK:

// vtkPolyData* mesh ....
auto mesh_mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
mesh_mapper->SetInputData(mesh);
auto mesh_actor = vtkSmartPointer<vtkActor>::New();
mesh_actor->SetMapper(mesh_mapper.GetPointer());

renderer->AddActor(mesh_actor);


VTK shows my planes but the mesh and planes aren't aligned correctly.
Shouldn't they be aligned since my bounds and centroid are equal?  How do
they get unaligned?
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