1. Teddy: A Sketching Interface for 3D Freeform Design Takeo Igarashi University of Tokyo Satoshi Matsuoka, Hidehiko Tanaka Tokyo Institute of Technology SIGGRAPH 1999

2. List 1.Abstract 2.Introduction 3.Related Work 4.User Interface 5.Modeling Operations 6.Algorithm 7.Implementation 8.User Experience 9.Future Work 1. Overview 2. Creating a New Object 3. Painting and Erasing on the Surface 4. Extrusion 5. Cutting 6. Smoothing 7. Transformation 1. Creating a New Object 2. Painting on the Surface 3. Extrusion 4. Cutting 5. Smoothing

3. Abstract * Sketching Interface for 3D Freeform Design Sketching interface for quickly and easily designing freeform models User draws 2D freeform strokes interactively System constructs 3D polygonal surface automatically System supports several modeling operations Inflating the region surrounded by the silhouette

4. Abstract ** Teddy Prototype system Java program Mesh construction is done in real-time User Study (for first-user) Mastering the operations : 10 minutes Constructing interesting 3D models : minutes

5. 1. Introduction * Creating Freeform Surfaces is difficult & tedious SKETCH This paper extends ideas of SKETCH Using Freeform strokes as expressive design tool User draw 2D freeform strokes interactively System constructs a 3D polygon surface models based on the strokes Editing operations by strokes Resulting models have a hand-crafted feel

6. Movies

7. SKETCH: An interface for sketching 3D scenes Modeling 3D Object by Sketch Interface Legends of strokes CSG subtraction

8. 1. Introduction ** Paper Sketch Interface Algorithms for constructing 3D shapes from 2D strokes Implementation of our prototype system, Teddy Geometric representation Standard polygonal mesh Interface can be used to other representation Volumes or metaballs metaball

9. 1. Introduction *** Design Goal of Teddy Construction of approximate models Not for careful editing of precise model Interactive Real-time pen-and-ink rendering Java on mid-range PC

10. 1. Introduction **** Obvious Application of Teddy Design of 3D models for character animation Rapid prototyping in the early stages of design Educational/recreational use for non-professionals and children Real-time communication assistance on pen-based system

11. Figure 2:Painted models created using Teddy and painted using a commercial texture-map editor

12. Applications PC package MagicalSketch 2 Gamecube game Playstation2 game

13. 2. Related Work * Geometric Modeling Typical procedure - Start with a simple primitives Successive transformation Combination of multiple primitives Transformation Techniques - User create various precise, smooth models interactively Deformation  [15] Free-form deformations with lattices of arbitrary topologyFree-form deformations with lattices of arbitrary topology  [23] Wires: a geometric deformation techniqueWires: a geometric deformation technique Shape manipulation  [8] Visual interfaces for solids modeling Construct complex model

14. Free-form deformations with lattices of arbitrary topology R. MacCracken and K.I. Joy. SIGGRAPH 96 Generalize Previous FFD Lattices of Arbitrary Topology Use Catmull-Clark subdivision

15. Wires: a geometric deformation technique K. Singh and E. Fiume SIGGRAPH 98 Wire curve is shape’s deformable features

16. 2. Related Work ** Implicit Surfaces ( Skeleton Models ) User specifies the skeleton of model System construct smooth, natural-looking surfaces  [3] Interactive techniques for implicit modeling [3] Interactive techniques for implicit modeling  [18] Polygon inflation for animated models: a method for the extrusion of arbitrary polygon meshes. Surface inflation method  [17] Object modeling by distribution function and a method of image generation

17. Interactive techniques for implicit modeling J. Bloomenthal and B. Wyvill 1990 Symposium on Interactive 3D Graphics User control its skeleton, system compute corresponding implicit surface automatically

18. 2. Related Work *** This paper User specify the silhouette of shape instead of skeleton Inspired by previous sketch-based modeling system  Inferring 3D models from freehand sketches and constraints  SKETCH: An interface for sketching 3D scenesSKETCH: An interface for sketching 3D scenes Interpret user’s stroke and construct 3D rectilinear model Goal of this paper Interface for designing rounded freeform models

19. 2. Related Work **** Inflation of a 2D drawing Shading in Two Dimensions 3D surface editing based on 2D painting  3D Paint 3D Paint Target is 2D array with associated height values Rather than 3D polygon Using 3D Input/Output Devices  The Holosketch VR sketching system.

20. 3D Paint L. Williams 1990 Symposium on Interactive 3D Graphics Extend Drawing, painting metaphor to 3 rd dimensions Surface is Height Value of 2D Arrays

21. 2. Related Work **** Freeform Strokes for 2D Application Specifying gestural command  Ambiguous intentions: A paperlike interface for creative design  Interactive sketching for the early stages of user interface designInteractive sketching for the early stages of user interface design Specifying 2D curve  A mark-based interaction paradigm for free-hand drawing Editing curve by sketching Merits Find the best matching arcs or splines automatically Freeing the user from explicit control of underlying parameter

22. Interactive Sketching for the Early Stages of User Interface Design J.A. Landay and B.A. Myers. 1995 CHI SILK Interface designers sketch the interface system produces application based on sketch automatically

23. 2. Related Work ***** Volumetric representation Volume sculpting  Sculpting: an interactive volumetric modeling technique Sculpting: an interactive volumetric modeling technique Useful for designing topologically complicated shapes Mesh-construction algorithm Fundamental representation for geometric modeling and CG Based on a variety of work on polygonal mesh manipulation  Mesh optimization  Shape design : Free-form shape design using triangulated surfaces  Surface fairing : A signal processing approach to fair surface design

24. Sculpting: an interactive volumetric modeling technique T. Galyean and J.F. Hughes 1991 SIGGRAPH Sculpting 3D Voxel Data Controlling by 3D Devices

25. 3. User Interface Physical User Interface Traditional 2D input devices Mouse or tablet Interface Do not use WIMP-style direct manipulation techniques WIMP = window, icon, menu, pointer Standard interface widget Button, menu … Use only freeform strokes on the screen

26. 4. Modeling Operation Modeling Operation from the User’s point of view Operations are executed after user complete a stroke Not Supported Creation of Multiple Objects and combining single object Model must have a spherical topology E.g torus (x) Strokes do not intersect Basic Operations Creation, Painting, Extrusion, cutting, erasing

27. 4.1 Overview Basic Operation and Result Summarizing the modeling operation available

30. Figure 5: example of Creation Operation (top: Stroke, middle: result, bottom: rotation)

31. Figure 6: example of Extrusion (top: extruding stroke, bottom: result of extrusion) Figure 7: More Extrusion Operation (digging cave, drawing)

32. Figure 8: Cutting Operation Figure 9: Extrusion After Cutting

33. Figure 10: Smoothing Operation

34. Figure 11: Examples of Transformation (top: bending, bottom: distorting)

35. 5. Algorithm How the system constructs a 3D polygonal mesh from the user’s freeform strokes Creation and extrusion Freeform surface construction based on skeleton Input Strokes is Resampled To remove noise in the handwriting input strokes To construct a regular polygonal mesh Smooth polyline with uniform edge length

36. 5.1 Creating a New Object* Overall Procedure 1.Closed planar polygon 2.Spine or axes of the polygon 3.Elevate vertices of the spine 4.Polygonal mesh wrapping the spine

37. 5.1 Creating a New Object** Figure 13: Finding the Spine

38. 1. Closed planar polygon (13a) All edges has predefined unit length External edge: initial polygon Internal edge: edges added in the triangulation - Triangulation (13b) Constraint Delaunay Triangulation Terminal triangle: 2 external edges Sleeve triangle: 1 external edges Junction triangle: 0 external edge 5.1 Creating a New Object ***

39. 5.1 Creating a New Object **** 2. Spine or axes of the polygon Spine by Chordal Axis (13c) Connecting the midpoint of the internal edges PruningPruning (13d) Pruned spine (13e) Chordal axis of remaining sleeve and junction triangles Subdivision of sleeve and junction triangle (13f)

40. 5.1 Creating a New Object ***** Pruning Merge triangles Removing interior edge Triangulation with a fan Stop 1: Some vertex lies outside the semicircle Stop 2: Newly merged triangle is a junction triangle

41. 5.1 Creating a New Object ****** 3. Elevate vertices of the spine Average distance between vertex and external vertex directly connected to the vertex (b) 4. Polygonal mesh wrapping the spine Elevate fan edge is converted to a quarter oval (c) Sewing together the neighboring elevated edge (d)

42. 5.2 Painting on the Surface Create surface line Projecting each line segment of the input stroke onto the object’s surface polygon Method 1. Calculate bounded plane 2. Find intersections between plane and polygon Only nearest intersecting polygon is used

43. 5.3 Extrusion* Creating new polygonal meshes Stroke:Closed base surface line (base ring) Extruding stroke Method Base ring sweep along the projected extruding stroke Figure 17: Extrusion Algorithm

44. 5.3 Extrusion** 1. Producing 3D extruding stroke Find the plane for projection Project 2D extruding stroke onto the plane 2. Pointer Advancing Create copy of the base ring along the extruding stroke 3. Delete original polygon surrounded by the base ring 4. Create new polygon by sewing adjacent rings

45. 5.3 Extrusion*** Point Advancing Advancing from two end pointer (left, right) Three possibility Left pointer / Right pointer / both Goodness value Increases angle between line connecting two pointers and direction of strokes Figure 18: Sweeping the Base Ring

46. 5.3 Extrusion**** User draw unexpected extruding stroke or base surface is not sufficiently planar Figure 19: Unintuitive Extrusions

47. 5.4 Cutting Based on the painting algorithm 1.Projected onto the front and back facing polygon 2.Connects the corresponding end points of the projected edges to construct a planer polygon 3.Triangulating planer polygon 4.Removing all polygons to the left of the cutting strokes Figure 20: Cutting

48. 5.5 Smoothing Determine of Z-value of Vertex Bazier curve between two end-point of the ring on 2D plane Figure 21: Smoothing Algorithm

49. 6. Implementation* Prototype : 13000 line Java program Test Devices Display-integrated tablet (Mutoh MVT-14) Electric whiteboard (Xerox Liveboard) Standard mouse Speed Mesh construction process is real-time if model becomes complicated, it causes a short pause

50. 6. Implementation** Figure 2 3D models created with Teddy Painted using a commercial texture-map editor Chameleon Results reflect the hand-drawn nature of the shape Quite different from 3D models created in other modeling system

51. 7. User Experience Feedback of Teddy Quite intuitive Explore various 3D design Observation of how first-time users learn teddy Create their own models fluently within 10 minutes 5 minutes : tutorial 5minutes : guided practices It takes a few minutes to Create stuffed animal

52. 8. Future Work Algorithms and Implementation are Robust, Efficient Intuitive result, when user draw unexpected strokes Research Direction Develop additional modeling operation Support a wider variety of shapes with arbitrary topology Allow more precise control of the shape Possible Operation Create crease Twisting the models Specifying the constraints between the separate parts for animation system

53. Further Research Chameleon : 3D Paint for Teddy Paint on 3D Model System Makes 2D Texture Automatically Application Movies

54. Further Research SmoothTeddy 3D Modeling and Painting System Application Movies