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  1. Computer Graphics Research at Virginia David Luebke Department of Computer Science

  2. Outline • Why I like graphics • My current research • VDS • Gaze • NPR • Scanning Monticello

  3. Why Graphics? • Graphics is cool • I like to see what I’m doing • I like to show people what I’m doing • Graphics is interesting • Involves simulation, algorithms, architecture… • Graphics is moving quickly • Intel vs. nVidia... • Graphics is fun • Graphics is important

  4. Why Graphics? • Entertainment: Cinema Universal: Jurassic Park Pixar: Geri’s Game

  5. Why Graphics? • Entertainment: Games id: Quake II Cyan: Riven

  6. Why Graphics? • Medical Visualization The Visible Human Project MIT: Image-Guided Surgery Project

  7. Why Graphics? • Computer Aided Design (CAD)

  8. Why Graphics? • Scientific Visualization

  9. Outline • Why I like graphics • My current research • VDS: View-Dependent Simplification • Gaze • Art-Based Rendering • Scanning Monticello

  10. The Problem:Massive Model Rendering • Problem: interactive visualization of very complex environments • Who cares? • Scientific visualization • Medical visualization • Computer Aided Design (CAD )

  11. Massive Model Examples:Aerospace CAD • Cassini space probe model • 415,000polygons Courtesy Jet Propulsion Laboratory

  12. Massive Model Examples:Maritime CAD • SubmarineTorpedoRoom • 700,000polygons Courtesy General Dynamics, Electric Boat Div.

  13. Massive Model Examples:Structural CAD • Coal-firedpower plant • 13 millionpolygons Courtesy ABB Engineering

  14. Massive Model Examples: More Maritime CAD • Double Eagle container ship • 82 million polygons Courtesy Newport News Shipbuilding

  15. The Holy Grail… Deussen et al: Realistic Modeling of Plant Ecosystems

  16. Level of Detail • The problem: • Polygons rule the world(of interactive graphics) • Polygonal models are often too complex to render at interactive rates • One solution: • Level-of-detail methods simplify the polygonal geometry of small or distant objects

  17. Level of DetailTraditional Approach • Create levels of detail (LODs) of objects: 249,924 polys 62,480 polys 7,809 polys 975 polys Courtesy IBM

  18. Level of Detail:Traditional Approach • Distant objects use coarser LODs:

  19. Limitations ofTraditional LOD • Most algorithms are: • Too fragile for messy CAD models • Too slow for large CAD models • Not suited for drastic simplification

  20. Drastic Simplification: Large Objects Courtesy IBM and ACOG

  21. Drastic Simplification: Small Objects Courtesy Electric Boat

  22. Drastic Simplification:Preserving Topology • Rotor model: • 21 holes • 4736 faces Courtesy Alpha_1 Project, University of Utah

  23. Drastic Simplification:Preserving Topology 21 holes, 1006 faces 1 hole, 46 faces

  24. The Problems WithDrastic Simplification • For drastic simplification: • Large objects must be subdivided • Small objects must be combined • Topology must be simplified • Difficult or impossible with traditional LOD

  25. A New Approach • Dynamic: simplify objects on the fly • View-dependent: account for viewpoint • Global: simplify scenes, not objects • Automatic: simplify without user’s help

  26. Dynamic Level of Detail • A relatively recent departure from the traditional static approach: • Static LOD: create individual LODs in a preprocess • Dynamic LOD: create data structure from which a desired level of detail can be extracted at run time.

  27. View-Dependent LOD: Examples • Show nearby portions of object at higher resolution than distant portions View from eyepoint Birds-eye view

  28. View-Dependent LOD: Examples • Show silhouette regions of object at higher resolution than interior regions

  29. View-Dependent LOD: Examples • Show more detail where the user is looking than in their peripheral vision: 11,726 triangles

  30. View-Dependent LOD: Examples • Show more detail where the user is looking than in their peripheral vision: 34,321 triangles

  31. Dynamic LOD: How Does It Work? • So…dynamic LOD is great, but how do we implement it? • Basically, with one big data structure: the vertex tree • Represents the entire model • Hierarchy of all vertices in model • Queried each frame for updated scene

  32. The Vertex Tree • Each vertex tree node contains: • A subset of model vertices • A representative vertex or repvert • Folding a node collapses its vertices to the repvert • Unfolding a node splits the repvert back into vertices

  33. Vertex Tree Example 8 7 R 2 I II 10 6 9 3 10 A B C 3 1 1 2 7 4 5 6 8 9 4 5 Vertex tree Triangles in active list

  34. Vertex Tree Example 8 7 R A 2 I II 10 6 9 3 10 A B C 3 1 1 2 7 4 5 6 8 9 4 5 Vertex tree Triangles in active list

  35. Vertex Tree Example 8 R A I II 10 6 9 3 10 A B C 3 1 2 7 4 5 6 8 9 4 5 Vertex tree Triangles in active list

  36. Vertex Tree Example 8 R A I II 10 6 9 3 10 A B C 3 B 1 2 7 4 5 6 8 9 4 5 Vertex tree Triangles in active list

  37. Vertex Tree Example 8 R A I II 10 9 3 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  38. Vertex Tree Example 8 R A C I II 10 9 3 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  39. Vertex Tree Example R A C I II 10 3 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  40. Vertex Tree Example R A C II I II 10 3 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  41. Vertex Tree Example R A II I II 10 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  42. Vertex Tree Example R A I II I II 10 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  43. Vertex Tree Example R I II I II 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  44. Vertex Tree Example R I II I II R 10 A B C 3 B 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  45. Vertex Tree Example R I II R 10 A B C 3 1 2 7 4 5 6 8 9 Vertex tree Triangles in active list

  46. 8 A 10 6 9 3 4 5 The Vertex Tree:Tris and Subtris 8 7 Fold Node A 2 10 6 9 3 UnfoldNode A 1 4 5 Node->Tris: triangles that change shape upon folding Node->Subtris: triangles that disappear completely

  47. Each node’s tris and subtris can be computed offline to be accessed very quickly at run time This is the key observation behind dynamic simplification The Vertex Tree:Tris and Subtris

  48. Outline • Why I like graphics • My current research • VDS • Gaze: gaze-directed rendering • NPR • Scanning Monticello

  49. Gaze-Directed Rendering • View-dependent rendering opens up a new door: gaze-directed rendering • Track the user’s eye gaze • Give more detail to region of interest, less elsewhere

  50. Gaze-Directed Rendering: ERICA • Problem 1: how to do eye tracking? • Answer ERICA project (Prof. Hutchinson) • Main uses: disabled access, gaze analysis • ERICA pros: • non-intrusive eye tracking • 60 Hz, ~1 cm accuracy • ERICA cons: • No windows (working on it) • Head must stay very still (working on it) • Currently a bit bulky (working on it)