User talk:JRobinson

Dear All,

The specific behaviour that I wanted was to be able to position the vtkPlaneWidget according to the origin and normal of an existing vtkPlane. The converse already exists with vtkPlaneWidget::GetPlane(vtkPlane*). THe problem with trying to use existign vtkPlaneWidget methods is the lack of

this->PlaneSource->Update();

in the SetNormal & SetOrigin methods. The workaround was to add a new method to vtkPlaneWidget:

void vtkPlaneWidget::SetPlane(vtkPlane *plane)
{
  if ( plane == NULL )
    {
    return;
    }
  float normal[3] ;
  float origin[3] ;
  plane->GetNormal(normal) ;
  plane->GetOrigin(origin) ;
  this->SetNormal(normal) ;
  this->SetCenter(origin) ;
  this->PlaneSource->Update();
}

Now I can set the initial vtkPlaneWidget position according to an existing vtkPlane orientation and update it at any time. Part of my code looks like this:

/////////////////////////////////////////////////////////////////////////////
// CSampleDoc commands
/////////////////////////////////////////////////////////////////////////////
void CSampleDoc::SetUpPlaneWidget()
{
    pPlaneWidget->SetInteractor(GetView()->Interactor);
// Just to get overall dimension
    pPlaneWidget->SetInput(pUnstructuredGrid);
// Make it slightly bigger than the actual cross section
    pPlaneWidget->SetPlaceFactor(1.25);
    pPlaneWidget->PlaceWidget();
// This is not pertinent unless the wireframe representation is used 
    pPlaneWidget->SetResolution(10) ;

// Choose your representation
    pPlaneWidget->SetRepresentationToOutline() ;
//    pPlaneWidget->SetRepresentationToWireFrame() ;
//    pPlaneWidget->SetRepresentationToSurface() ;

// Make sure it corresponds to the vtkPlane orientation
    UpdatePlaneWidget() ;

// Make sure that reacts   
    pPlaneWidget->AddObserver(vtkCommand::InteractionEvent, pCutPlaneCallback);

}
/////////////////////////////////////////////////////////////////////////////
// CSampleDoc commands
/////////////////////////////////////////////////////////////////////////////
void CSampleDoc::UpdatePlaneWidget()
{
// This method is to update the plane widget from the vtkPlane used as the 
// implicit function for the vtkCutter
    pPlaneWidget->SetPlane(pPlane) ;
    pPlaneWidget->UpdatePlacement() ;
}

I hope this is of some use. If i am doing something obviously wrong or inefficient, please add your comments to the Wiki. Might I suggest to the powers that be that the method that I have added to my vtkPlaneWidget object be added to teh actual next build/release of the vtkHybrid library (and any other objects that could use such a functionality).

Jim