2009 Winter Project Week Transform Management

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MRML scene graph.

Transform node in a MRML scene.

Key Investigators

• Jim Miller, GE
• Steve Pieper, Isomics, Inc.

Objective

Provide the infrastructure to handle non-linear transformations as both modeling and resampling transforms.

Approach, Plan

We will continue the plans from the Summer 2008 project event (here).

• Add attribute to transform nodes to indicate whether they represent a "Transform to World/Parent" or "Transform from World/Parent"
• Extend visualization system for "Transform to World/Parent" or "Transform from World/Parent" _
• Extend command line modules to annotate a transformation as a "Transform to World/Parent" or "Transform from World/Parent"
• Identify places in slicer3 code where linear transforms are assumed - these either need generalization or informative warning/error messages
• Incorporate itkDisplacementFieldTransform/vtkGridTransform for vector field style transformations.
  • Need to extend itk::TransformIO. Prototype using Base64/Zipped vector fields. Alternative, allow binary data in ITK Transform files or reference an external image to hold vectors in file format.
• Coordinate frame manager to map between any two data sets verses mapping to parent/world.

Progress

• Linear transformations are always stored in Slicer as modeling transformations.
• Slicer assumes that plugins using ITK Transform file format want/return resampling transforms
• Initial prototype of itkDisplacementFieldTransform using ITK Transform file format by Base64 encoding a Zipped version of a vector field (ITK Transform format is ASCII).
• Mike Halle has a coordinate frame manager written in Python