Kizamu: A System For Sculpting Digital Characters

1
Kizamu A System For Sculpting Digital Characters

• SIGGRAPH 2001
• Ronald N. Perry
• Sarah F. Frisken

2
Introduction

• Kizamu
• A computer-based sculpting system for creating
  digital characters
• To carve in Japanese

3
Motivation

• Digital character model
• Smooth surface
• Fine detail
• Clay
• Polygon
• NURBS
• Subdivision surfaces

4
Motivation

• Requirements for sculpting system
• Digital clay
• Smooth surfaces, fine detail
• Undo, duplicate, store permanently
• Standard hardware
• Standard input, output
• ADFs
• Integrate volume and surface into a single
  representation
• Can be combined by simple CSG operations

5
Background

• ADFs
• Adaptively Sampled Distance Fields
• S. Frisken, R. Perry Adaptively Sampled Distance
  Fields A General Representation of Shape for
  Computer Graphics, Proc. GIGGRAPH 00

6
Kizamu

• Contributions
• Volumetric sculpting interface
• Advances in ADF generation, editing
• Several new ADF rendering approaches
• Methods for inputting and outputting models
• Input scanned range image
• Output triangle model at various LOD

7
Related Work

• Meta-clay
• Metaballs
• Density based object representation
• Does not represent edges, corners, fine detail
• FreeForm
• 3 degree-of-freedom haptic input device (force
  feedback)
• Sampled intensity values (regularly sampled
  volume)
• Marching cubes (memory overlaed)

8
The Sculpting System
9
Interaction Paradigms

• Surface following
• Guide the tool position and orientation
• Bezier tool paths
• Scripting of the tool path
• Distance-based constraint
• Control point editing

10
Generating ADFs

• Bottom-up
• Excessive amount of memory
• Too many distance computations
• Top-down
• Expensive octree neighbor searches
• Requires many redundant distance computations
• Poor performance
• Level-8 ADF 20 sec (Pentium III)
• Level-9 ADF 40 sec (Pentium III)

11
Tiled Generation

• Better memory utilization
• Cache optimized
• Reuse of distance computations
• Tile
• Distance value are stored
• Bit flags
• Reuse flag
• Performance
• Level-8 ADF 1 sec (Pentium III)
• Level-9 ADF 2 sec (Pentium III)

12
Editing

• ADF local editing
• Procedurally generated tool paths
• A script of sculpting operations
• Maintaining the stroke history
• Correcting the remote field
• Differencing tool
• Dist(p)min(distobj(p), -disttool(p))
• Additive tool
• Dist(p)max(distobj(p), disttool(p))

13
Rendering

• Global rendering (global view change)
• Triangle
• Rendered through OpenGL
• Generate 200,000 triangles 0.37s on a P4
• Point
• Point-based rendering
• 800,000 Phong illuminated points in 0.2 s

14
Rendering

• Local rendering (locally update)
• Ray casting
• Adaptive / non-adaptive
• Local triangle regeneration
• Triangles of affected cell are deleted, new ones
  regenerated.
• requires memory

15
Fitting Kizamu Into the Character Animation
Pipeline

• Input from range data
• Wheelers algorithm
• Each range image is converted to a range surface
  triangle mesh
• Create an octree using a probability-weighted
  function
• Marching cube
• Enhances the algorithm using ADFs

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Triangulating ADFs

• Properties
• Topologically consistent
• Fast
• LOD
• Methods
• Vertex at the cell center
• Vertices of neighboring cells are joined
• Vertices are moved towards the surface
• LOD
• Boundary leaf cell -gt leaf cell (error threshold)

17
Conclusion

• Integrating ADFs
• Shape representation
• High resolution digital sculpting
• Intuitive to use
• Efficient in memory usage and processing
• Several new algorithms and approaches
• Interface
• Efficient generation, editing
• Rendering approaches

18
Future work

• Digital animation
• Generating NURBS
• Volumetric representation
• Deformation
• Volumetric characters