[vtkusers] Using a boxwidgets transform to rotate a non-vtk 3D model?

[Totte Karlsson]

Hello Cory,
I was able to use your suggestion and got some code to work, as follows:

     virtual void Execute(vtkObject *caller, unsigned long, void*)
     {
         static int callCount = 0;
         static double lastAngle = 0;
         static double lastVec[3] = {0,0,0};
         vtkSmartPointer<vtkTransform> t = 
vtkSmartPointer<vtkTransform>::New();
         static vtkSmartPointer<vtkTransform> lastTransform = 
vtkSmartPointer<vtkTransform>::New();
         vtkBoxWidget *widget = reinterpret_cast<vtkBoxWidget*>(caller);
         widget->GetTransform(t);

         double* wxyz = t->GetOrientationWXYZ();
         double* lastWXYZ = lastTransform->GetOrientationWXYZ();

         if(anActor)
         {
             cout<<"CallCount: "<<callCount<<"Current Angle 
"<<wxyz[0]<<" Effective angle:"<< wxyz[0] - lastAngle<<endl;

             //Transform 'back'
             anActor->RotateWXYZ(-lastAngle, lastWXYZ[1], lastWXYZ[2], 
lastWXYZ[3]);
             anActor->RotateWXYZ(wxyz[0], wxyz[1], wxyz[2], wxyz[3]);
         }

         //Save transform data
         lastAngle = wxyz[0] ;
         lastVec[0] =wxyz[1];
         lastVec[1] =wxyz[2];
         lastVec[2] =wxyz[3];

         lastTransform = t;
         callCount++;
     }

In the above code, two transformations of the actor are done, in order 
to follow the orientation of the widget. 1) to rotate the actor to its 
initial position, and 2), applying current transformation.

Although the above code works, is there a way to get the 'incremental' 
transform somehow? I'm a novice about these things so sorry if asking 
something obvious...

tk


On 8/6/2015 7:40 AM, Cory Quammen wrote:
> TK,
>
> You can get the orientation in angle-axis representation with
>
> double wxyz[4];
> t->GetOrientationWXYZ(wxyz);
>
> From the docs [1]:
>
> The angle (w) is in degrees and the axis (xyz) is a unit vector.
>
> You should be able to apply this rotation to your molecule model's 
> RotateAboutVector function.
>
> HTH,
> Cory
>
> [1] 
> http://www.vtk.org/doc/nightly/html/classvtkTransform.html#aa8244cbab95a2dbb20e94af6e7f16b7f
>
>
> On Wed, Aug 5, 2015 at 8:54 PM, Totte Karlsson 
> <totte at dunescientific.com <mailto:totte at dunescientific.com>> wrote:
>
>     Hello,
>     I'm using vtk to visualize 3D models of molecules.
>     The actual molecular model is decoupled from vtk code, and
>     visualization is implemented using a model-view kind of design.
>
>     Currently I have the following challenge. If a user wants to
>     manipulate the absolute orientation of the molecule, it is done by
>     manipulating the underlying model using rotation functions, like
>     RotateX, RotateY, RotateAboutVector, and translation functions
>     TranslateX, Y etc.
>
>     For now 3D rotations are simply done using two scrollbars, one
>     horizontal and one vertical, causing the underlying model being
>     rotated about the vtk viewUP vector and the vtk cameraPlane normal
>     respectively.  This works fine, but is not so intuitive for the user.
>
>     Instead I believe allowing interaction with something like a box
>     widget that encapsulates the molecule view, (with disabled
>     handles), would be better.
>
>     The challenge is how to figure out how to capture the boxwidgets
>     orientation in a callback, and using this information in order to
>     manipulate the underlying molecular model.
>
>     For example, a boxwidget callback (from boxwidget example at
>     http://www.vtk.org/Wiki/VTK/Examples/Cxx/Widgets/BoxWidget):
>
>     class vtkMyCallback : public vtkCommand
>     {
>         public:
>             static vtkMyCallback *New()       { return new
>     vtkMyCallback;    }
>
>         virtual void Execute(vtkObject *caller, unsigned long, void*)
>         {
>             vtkSmartPointer<vtkTransform> t =
>     vtkSmartPointer<vtkTransform>::New();
>             vtkBoxWidget *widget =
>     reinterpret_cast<vtkBoxWidget*>(caller);
>             widget->GetTransform(t);
>
>             double* angles?? = t->GetOrientation();
>             if(aMoleculeModel)
>             {
>                 //Use some secret(!) code to manipulate orientation of
>     a molecule to 'rotate' it together with the boxWidget
>                 aMoleculeModel->RotateZ(??);
>                 aMoleculeModel->RotateY(??);
>                 aMoleculeModel->RotateZ(??);
>             }
>         }
>         Molecule* aMoleculeModel;
>
>     Anyone seeing how to do this or have some pointers?
>
>     Cheers,
>     tk
>
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>
> -- 
> Cory Quammen
> R&D Engineer
> Kitware, Inc.

-- 
------------------------------------------------------------------------
<http://www.dunescientific.com/> 				
Totte Karlsson: totte at dunescientific.com 
<mailto:totte at dunescientific.com> or (425) 780-9648 
<tel:%20425%20%20780-9648>
http://www.dunescientific.com/
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