Introduction

Although 3D Slicer provides an architecture to customize its view widgets and rendering, implementing new widgets is a significant challenge.

To properly function a significant number of elements need to be created / assembled / manipulated :

• A MRML Node to store the display information and trigger the creation of the VTK pipelines from the scene

• A Displayable Manager responsible for creating a VTK pipeline based on the type of view / information present in the MRML node.

• A VTK render window to add new renderers if our widget needs to be displayed in overlay

• The actual VTK widget / representation for handling the user events

• …

Implementing and connecting all these elements have restricted the implementation of new displayable managers to 3D Slicer expert developers.

For new developers, it was mainly recommended for interactive behaviors to:

• Compose existing nodes in Python and use markups points for interactivity

• Fetch access to the render window from the Qt widgets and directly inject their actors

The LayerDM library was created to ease the creation of new VTK pipelines by:

• Automating a lot of boilerplate

  • Pipeline creation/removal mechanism based on scene nodes

  • Camera synchronization

  • Renderer layer creation / removal

  • Rendering reactivity based on object’s event

• Providing a simple API

  • Explicit pipeline creation callbacks

  • Python bridges and wrapping

  • Improved event processing order

  • Access to sibling pipelines

Note

The library doesn’t replace the current displayable manager system but is integrated into it making it fully compatible with existing displayable managers and event processing mechanism.

Installing the extension

The library can be installed through the extension manager.

Once the library is installed, you can checkout the examples to get started developing your own pipelines.