Slicer3:Volume Rendering

Test the module

• Copy the following folder from the svn repository http://www.na-mic.org/svn/Slicer3/trunk/Base/GUI/Testing/VolumeRendering to the following path <YourSlicerBuildDir>\lib\Slicer3\Modules\Packages\VolumeRendering.
• Restart Slicer
• Load a MRML-Scene (e. g. tutorial.xml from the Tutorial Dataset)
• Go to the module dropdown and select VolumeRendering
• Select "all" (if you use the tutorial dataset) as the Source Volume and click LoadNode =>The volume rendered Volume should appear.
• Play with the transfer function etc.
• Note: After changing a setting please click on the volume one time to load the new settings

Latest results and limitations

Description

• Loading of MRML-Nodes is possible
• At the moment no removing of MRML-Nodes possible
• Change properties
• Calculate transfer functions automatically
• No performance tuning at all
• Shading

Screenshots

volume rendered label map of the tutorial dataset

volume rendered label map of the tutorial dataset, shading enabled

shading enabled, linear interpolation, automatich mapping for bones

next Tasks

• Develop different algorithms for labelmap and grayscale volumes -----algorithm for grayscale is missing => new task: presets
• Find Presets, see also at goals
• Try to reduce artefacts in labelmaps by using several RGB points in the mapping function -----done, artefacts still there?
• Implement a possibility to change between different volumes during runtime -----done
• Have a closer look on the final calculation of the renderer-----Problems, when interrupting outside renderWindow
• Detect if video card can use 3d Texture Mapping or not, if not use MIP, -----done, there are two new Buttons to simulate having openGl support or not. standard preset is now MIP (performance issue)
• Add possiblity to change opacity (for labelmaps) -----done, slider
• Include code to make all models invisible(Good for testing) -----done, new button
• Have a closer look on the gradient opacity mapper, when using label maps

Problems

• Cannot load the following data
  • spgr (grayscale): tutorial data set (freezes)-----fixed: problems with automatic mapping
  • grayscale (greyscale): brain atlas (freezes)-----fixed:problems with automatic mapping
  • seg (LabelMap): abdomen data set (not freezing, seems to render, but unvisible)

Goals

Volume rendering presets :

• MIP (Maximum Intensity Projection)
  • Wikipedia
  • vtkFixedPointVolumeRayCastMapper Class Reference
• CT Bone and vessel
  • Use Hounsfield units
    • Bone +400->+1000
    • Soft tissue +40->+80
    • Water 0
    • Fat -60->-100
    • Lung -400->-600
    • Air -1000
  • Problem with Vessels: Different contrast mediums?!
• T1 MR Air/skin interface
• Label map per-label object rendering
  • Use the different MRMLNodes: vtkMRMLVolumeNode

Slicer3 module interface:

• Select from loaded volumes
• Specify preset transfer functions or use KWWidgets tools

Slicer3 internals:

• Correct coordinates including transforms
• Level of detail rendering
• Proper integration with surface rendering

Different Volume Rendering Algorithms

• RayCast
• 2D Texture Mapping
• 3D Texture Mapping
• ...

Wish List

• 2D Transfer functions - may require specialized opengl code integrated with VTK. Talk with Gordon about latest work from Utah.

• use glTexSubImage3D so that incremental changes to the volume can be quickly reflected