Skip to content

Latest commit

 

History

History
145 lines (97 loc) · 8.74 KB

DeveloperGuide.md

File metadata and controls

145 lines (97 loc) · 8.74 KB
Raw

Information for developers

This Slicer extension is in active development. The API may change from version to version without notice.

Build instructions

  • Build the extension against the newly built Slicer.
  • To start Slicer from a build tree and ensure the extension is properly loaded, consider running the SlicerWithVirtualReality launcher. For more details, see here.

Mapping of Controller Action to VTK event

The mapping process consists of two main steps:

  1. Parsing the vtk_open<vr|xr>_actions.json action manifest file to link controller-specific interaction paths with generic event paths. This file references controller-specific binding files, usually named vtk_open<vr|xr>_binding_<vendor_name>.json, where each controller interaction path is associated with a VTK-specific event path.

  2. Assigning a VTK event path to either a VTK event or a std::function. This association of a VTK event path involving a single controller with a VTK event is carried out in vtkOpen<VR|XR>InteractorStyle::SetupActions().

Action Manifest File

The controller interaction paths are specific to each backend:

As of Slicer@c7fe8657c, the provided vtk_open<vr|xr>_actions.json and vtk_open<vr|xr>_binding_<vendor_name>.json files in the vtkRenderingOpenVR and vtkRenderingOpenXR VTK modules are as follow:

OpenVR OpenXR
Action manifest url url
- HP Motion Controller url url
- HTC Vive Controller url url
- Microsoft Hand Interaction url
- Oculus Touch url url
- Valve Knuckles url url
- Khronos Simple Controller1 url

These files serve as essential references for mapping controller actions to VTK events.

Mapping of VTK event path

The association of VTK event paths to VTK events hardcoded in each VTK modules is as follow:

Complex Gesture Support

Recognition of complex gesture events commences when the two controller buttons mapped to the ComplexGesture action are pressed.

The SlicerVirtualReality implements its own heuristic by specializing the HandleComplexGestureEvents() and RecognizeComplexGesture() in the vtkVirtualRealityComplexGestureRecognizer class.

Limitations:

  • The selected controller buttons are exclusively mapped to the ComplexGesture action and cannot be associated with a regular action.

  • To workaround an OpenVR specific limitation, each button expected to be involved in the complex gesture needs to be respectively associated with /actions/vtk/in/ComplexGestureAction and /actions/vtk/in/ComplexGestureAction_Event2.

Useful Python Snippets

Activate virtual reality view:

import logging
import slicer

def isXRBackendInitialized():
    """Determine if XR backend has been initialized."""
    vrLogic = slicer.modules.virtualreality.logic()
    return vrLogic.GetVirtualRealityActive() if vrLogic else False

def vrCamera():
    # Get VR module widget
    if not isXRBackendInitialized():
        return None
    # Get VR camera
    vrViewWidget = slicer.modules.virtualreality.viewWidget()
    if vrViewWidget is None:
      return None
    rendererCollection = vrViewWidget.renderWindow().GetRenderers()
    if rendererCollection.GetNumberOfItems() < 1:
        logging.error('Unable to access VR renderers')
        return None
    return rendererCollection.GetItemAsObject(0).GetActiveCamera()


assert isXRBackendInitialized() is False
assert vrCamera() is None

vrLogic = slicer.modules.virtualreality.logic()
vrLogic.SetVirtualRealityActive(True)

assert isXRBackendInitialized() is True
assert vrCamera() is not None

Set virtual reality view background color to black:

color = [0,0,0]
vrView=getNode('VirtualRealityView')
vrView.SetBackgroundColor(color)
vrView.SetBackgroundColor2(color)

Set whether a node can be selected/grabbed/moved:

nodeLocked.SetSelectable(0)
nodeMovable.SetSelectable(1)

Related VTK modules

Footnotes

  1. https://registry.khronos.org/OpenXR/specs/1.0/html/xrspec.html#_khronos_simple_controller_profile ↩