Interactive Volume Rendering Using MultiDimensional Transfer Functions and Direct Manipulation Widge

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Interactive Volume Rendering Using
Multi-Dimensional Transfer Functions and Direct
Manipulation Widgets

• Joe Kniss Gordon Kindlmann Charles Hansen
• Presenter Xueqi Cheng
• Discusser Mahesh

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Volume Rendering

• Volume Rendering
• a technique for directly displaying a sampled 3D
  scalar field without first fitting geometric
  primitives to the samples.

Dataset 109 magnetic resonance(MR) slices
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Simian

• A volume rendering tool for scientific
  visualization and medical imaging.
• Features
• Multi-dimensional transfer functions
• Direct Manipulation Widgets
• Dual-domain interaction
• Shaded volumes

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Tansfer Function

• Role
• Mapping the voxel information to renderable
  optical properties like opacity and color.
• Voxel 3-D pixel
• Challenges
• Generation Manipulation
• Degrees of freedom
• Trial and Error
• Non-spatial

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Current Transfer Functions

• Current transfer functions
• 1-D transfer functions
• Opacity Color
• 2-D transfer functions
• Opacity Color
• Gradient magnitude how fast values are changing

GE Turbine Blade
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Multiple-Dimensional Transfer Function

• Good transfer function
• Reveal the important structures in the data
  without obscuring them with unimportant regions.

• 3D Transfer Function
• f (x) a function of position x
• f (x) how fast values are changing
• f (x) Added based on principle of edge
  detection
• Enable extracting complex boundaries between
  materials

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Multiple-Dimensional Transfer Function
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Direct Manipulation Widgets

• Conceptual gap between spatial and transfer
  function domains
• Spatial domain
• 3D space for the volume data to be rendered
• Transfer function domain
• abstract
• Direct manipulation widgets
• Link interaction in one domain with feedback in
  another

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Various Widgets

• Data Probe Widget
• reporting its tip position in
• volume space

• Clipping Plane Widget
• cut away parts of the volume
• map a slice of the volume to its surface

Spatial domain

• Lighting Widget
• control the light direction
• and color

• Transfer Function Widget
• present a graphical representation
• of the transfer function domain
• set and alter transfer function

Transfer function domain
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Transaction Function Widget

• boundary emphasis slider
• controls how the opacity
• changes as a function of second
• derivative magnitude

• classification widgets
• manually added
• specify regions of interest
• triangular rectangle

color picker widget
opacity scale
re-projecting a voxel queried in the volume
gradient threshold bar
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Dual-domain interaction

• Allow interaction happens in both domains
  simultaneously

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Hardware Considerations

• nVidia GeForce3!!

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Pros Cons

• Pros
• Multi-dimensional transfer functions help extract
  boundaries
• Interactive, visualized volume rendering
• Modern graphics hardware
• Cons
• Increased memory consumption