3-D Data

cs5984: Information Visualization

Chris North

Review

• Visualizing document collections:•

Where are we?

• Multi-D• 1D• 2D• Hierarchies/Trees• Networks/Graphs• Document collections• 3D

• Design Principles• Empirical Evaluation• Java Development• Visual Overviews• Multiple Views• Peripheral Views

3-D Data

• Surface data

• Volume data

Surface Data

• Vector/Polygonal surface data• Polygons approximate surfaces of 3D objects

• Paint textures on surfaces

• Examples:• Quake

•

VRML

• Protein example• http://www.rcsb.org/pdb/cgi/explore.cgi?job=graphics&pdbId=4TNA&page=&pid=16250983503380

Navigation

• Move camera

• Move objects

• 6 degrees of freedom:• 3 translation

• 3 rotation

• Zoom = translate forward?

y

z

x

x

y

z

Zoom

Graphics

• Projection• Z-buffer

• Shading, texture mapping, …

• Ray Tracing• Shoot rays from camera into scene

• Reflection, …

Challenges

• Navigation

• Occlusion, See inside?

Volume Data

• Voxel volume data• Fully sampled contents of 3D objects

• Voxel = 3D pixel; point in a 3D image

• Volume = 3D array

• Examples:• MRI, CaT scan:

» Measures tissue density at each point in space

• Visible Human» slice and photograph

2-D:

3-D:

Slicing

• Visible Human Explorer (north et al)• http://www.cs.umd.edu/hcil/visible-human/vhp.mpg

Slice and Dice

3D Cutting Plane• Ken Hinckley, UVA

Surface Reconstruction

• Generate surface data from volume data

• Iso-surfaces

• Marching Cubes algorithm

• 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

Transparency: X-Ray Vision

Surface Volumehttp://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• http://www.uke.uni-hamburg.de/institute/imdm/idv/vm3dn/io_thorax.en.html

Interactive Volume Rendering

• Kniss, “Interactive volume rendering with direct manipulation”

• Xueqi, Mahesh

3-D volume data: Digital Video

• 3D: Stack 2D video frames

time

x

y

Slicing Digital Video• Red’s Nightmare video in VHE• http://vtopus.cs.vt.edu/~north/infoviz/RedsNightmare.mpg

Full overview:

time

zoom

Scene change

still

credits

motion

Pan left

Assignment• Thurs: Workspaces

• Robertson, “Task Gallery”» supriya, varun

• Upson, “AVS”» christa, jun

• Dec 7: ACM CHI short papers due

• Dec 18: Project Final Paper due

• March: IEEE InfoVis papers due

Future

• Thanksgiving break

• Tues 27: Debates, 2D vs 3D• Kobsa, “Empirical comparison of comm infovis systems”

» kunal, zhiping

• Thurs 29: How (not) to lie with visualization• Other fun stuff?

Project Presentations

• Dec 4:

• Dec 6:

• Dec 11:

Upcoming Opportunities

• Independent studies

• Thesis projects

• GTAs

• GRAs