World Rotation in 3D

Support
1

Hi,

I have a question concerning the rotation of the whole VR Environment.
With the currently implemented OnPinch() and OnPan() Methods the whole environment can be scaled and moved. Now i want to use the OnRotate() method to rotate the whole world.

I think this is not working as in the OnPinch() method the vtkInteractorStyle3D::SetScale() method is called. Here the position of the HMD should be moved to compensate for the scaling. In a comment it is noted:

“New camera properties are overridden by virtual reality render window if head-mounted display is tracked”

Is this also the case for the rotation of the camera?

I tried:

vtkRenderWindowInteractor3D* rwi = static_cast<vtkRenderWindowInteractor3D*>(this->Interactor);
vtkCamera* camera = this->CurrentRenderer->GetActiveCamera();
double angle = rwi->GetRotation() - rwi->GetLastRotation();

  • camera->Roll(angle);
  • vtkSmartPointer<vtkTransform> transform = vtkSmartPointer<vtkTransform>::New();
    transform->PostMultiply();
    transform->Translate(0,0,0);
    transform->RotateY(angle);
    transform->Translate(camerPos[0], camerPos[1], camerPos[2]);
    -camera->SetPosition(transform->TransformPoint(camera->GetPosition()))

But nothing moves? Is there a workaround besides rotating every actor in the scene?

2

This is implemented in 3D Slicer’s VirtualReality extension. You may consider porting it back to VTK.

3

Thank you very much for the reply!!
I have taken a look at your extension. I tried to get the rotation working by setting the PhysicalToWorldMatrix:

vtkOpenVRRenderWindowInteractor* rwi = static_cast<vtkOpenVRRenderWindowInteractor*>(this->Interactor);
vtkOpenVRRenderWindow* rw = static_cast<vtkOpenVRRenderWindow*>(rwi->GetRenderWindow());

vtkCamera* camera = this->CurrentRenderer->GetActiveCamera();
double* cameraPos = camera->GetPosition();
double angle = rwi->GetRotation() - rwi->GetLastRotation();
double physicalScale = rwi->GetPhysicalScale();

vtkSmartPointer m = vtkSmartPointer::New();
rw->GetPhysicalToWorldMatrix(m);

vtkSmartPointer transform = vtkSmartPointer::New();
transform->PostMultiply();
transform->SetMatrix(m);
transform->RotateY(angle);

vtkSmartPointer tMInv = vtkSmartPointer::New();
vtkMatrix4x4::Invert(transform->GetMatrix(), tMInv);

rw->SetPhysicalToWorldMatrix(transform->GetMatrix());

The problem is, although the world can now be rotated, I see everything double until the end of the rotation. That means the original orientation of the Wolrd and its Objects remains visible as well as its currently rotated state until i exit the rotation mode - then i only see the correct rotated objects.
(I start the rotation by pressing the grip button on both controllers which calls the OnRotate() method)

Did you run into the same problems?

4

This should not happen. Maybe you need to update OpenVR driver to latest version and use very latest Slicer Preview Release.