3-D Information cs5764: Information Visualization Chris North Where are we? Multi-D 1D 2D 3D Hierarchies/Trees Networks/Graphs Document collections Design Principles Empirical Evaluation Navigation Strategies Visual Overviews 3-D Information Examples 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 VRML Protein example Navigation Move camera (POV) Move objects 6 degrees of freedom (DOF): 3 translation 3 rotation Zoom = translate forward? y z x x y z Zoom vs. Translation zoomtranslate 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 Volume Data 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 The problem: 2-D: 3-D: The Problem E.g. the Visible Human Whats inside? Slicing Visible Human Explorer (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 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 voxels contribution to image Interactive Volume Rendering Kniss, Interactive volume rendering with direct manipulation Transparency: X-Ray Vision SurfaceVolume Combining it all together Voxel-Man Hamburg University 3-D volume data: Digital Video 3D: Stack 2D video frames time x y Slicing Digital Video Reds Nightmare video in VHEFull overview: time zoom Scene change still credits motion Pan left