Transcript 3-D Information - Visual analytics

3-D Information
cs5764: Information Visualization
Chris North
Where are we?
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Multi-D
1D
2D
3D
Hierarchies/Trees
Networks/Graphs
Document collections
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Design Principles
Empirical Evaluation
Navigation Strategies
Visual Overviews
3-D Information Examples
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Universe, space
CAD/CAM, architecture
Physical objects, atomic structures, scientific data
physiological, MRI
Types of 3-D Information
• Surface data
• 2D analogy: vector graphics, geometric shapes
• Volume data
• 2D analogy: raster graphics, bitmaps, images
Surface Data
• Vector/Polygonal surface data
• Polygons approximate surfaces of 3D objects
• Paint textures on surfaces
• Examples:
• Quake
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VRML
• Protein example
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http://www.rcsb.org/pdb/cgi/explore.cgi?job=graphics&pdbId=4TNA&page=&pid=16250983503380
Navigation
y
• Move camera (POV)
• Move objects
• 6 degrees of freedom (DOF):
• 3 translation
• 3 rotation
x
z
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• Zoom = translate forward?
x
z
Zoom vs. Translation
zoom
translate
Graphics
• Projection
• Z-buffer
• Shading, texture mapping, …
• Ray Tracing
• Shoot rays from camera into scene
• Reflection, …
Challenges
• Navigation
• DOF
• Zoom, O+D, F+C?
• Occlusion, See inside?
• Manipulation
Overview+Detail
• Stoakley, “Worlds in Miniature”
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Volume Data
2-D:
• Voxel volume data
• Fully sampled contents of 3D objects
• Voxel = 3D pixel; tiny cube in a 3D image
• Volume = 3D array of voxels
• Examples:
• MRI, CaT scan:
» Measures tissue density at each point in space
• Visible Human
» slice and photograph
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• The problem:
3-D:
The Problem
• E.g. the Visible Human
• What’s inside?
Slicing
• Visible Human Explorer
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http://www.cs.umd.edu/hcil/visible-human/vhp.mpg
(north et al)
Slice and Dice
Overview+Detail
3D Cutting Plane
• Ken Hinckley, UVA
Surface Reconstruction
• Generate surface data
from volume data
• Iso-surfaces
• Marching Cubes
algorithm
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Look at cubes of 8 voxels
Cube is on surface if: ???
Generate polygons
Smooth
Volume Rendering
• Ray Casting
• Like x-ray
• Accumulate color
& opacity along rays
• “Transfer functions”
• Splatting
• Like projection
• Reverse of ray-casting
• Calculate each voxel’s
contribution to image
Interactive Volume Rendering
• Kniss, “Interactive volume rendering with direct
manipulation”
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Transparency: X-Ray Vision
Surface
Volume
http://www.uke.uni-hamburg.de/institute/imdm/idv/vm3dn/io_xray_combined.en.html
http://graphics.stanford.edu/software/volpack/movies/vp_movies.html
Combining it all together
• Voxel-Man
• Hamburg University
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http://www.uke.uni-hamburg.de/institute/imdm/idv/vm3dn/io_thorax.en.html
3-D volume data: Digital Video
• 3D: Stack 2D video frames
time
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Full overview:
Slicing Digital Video
time
zoom
• Red’s Nightmare video in VHE
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http://vtopus.cs.vt.edu/~north/infoviz/RedsNightmare.mpg
motion
Scene change
Pan left
still
credits