An Efficient Brush Model for Physically-Based 3D Painting - PowerPoint PPT Presentation

About This Presentation
Title:

An Efficient Brush Model for Physically-Based 3D Painting

Description:

Title: Simulating Chinese Brushwork Author: cpegnel Last modified by: cpegnel Created Date: 1/6/2002 6:51:13 AM Document presentation format: On-screen Show – PowerPoint PPT presentation

Number of Views:115
Avg rating:3.0/5.0
Slides: 32
Provided by: cpe110
Category:

less

Transcript and Presenter's Notes

Title: An Efficient Brush Model for Physically-Based 3D Painting


1
An Efficient Brush Model for Physically-Based 3D
Painting
  • Nelson S.-H. CHU (cpegnel_at_ust.hk)
  • Chiew-Lan TAI (taicl_at_ust.hk)
  • The Hong Kong University of Science and
    Technology
  • October 9, 2002, Beijing, China

2
Overview
  • Brush simulation for digital painting
  • Chinese brush
  • Physically-based
  • Interactive

3
Motivation
  • Digital painting
  • Convenient, easy to experiment
  • 2D mark-making methods
  • Works well for hard media like pastel
  • Spotted shape as brush footprint

Painting strokes made using commercial software
Corel Painter
4
Motivation
  • Chinese brush
  • Expressive lining instrument
  • Soft-yet-resilient quality
  • ????????? ??(??)
  • Deft manipulation
  • Spontaneous painting style
  • Spontaneity
  • Rhythmic vitality

5
Motivation
By Zhao Shaoang
6
Motivation
By Wu Guanzhong 1999
7
Motivation
  • Extend the expressiveness of Chinese brushes into
    digital domain
  • Help promote Chinese cultural heritage
  • Explore new possibilities for development
  • ????,????????,?????????? ???
  • Creates new computer graphics tools
  • High-quality calligraphic Oriental fonts
  • Non-photorealistic rendering of 3D objects

8
Previous Work
  • Stroke Appearance
  • Brush Model Painting Process

9
Previous Work
  • Stroke Appearance
  • B. Pham 91 (B-spline offset curves)
  • S. Hsu et al. 94 (Picture deformation)
  • Brush Model Painting Process

10
Previous Work
  • Stroke Appearance
  • Brush Model Painting Process
  • Geometric
  • S. Strassmann 86 (1D texture)
  • Painting Software Corel Painter (2D dab shape)
  • Physically-based
  • J. Lee 99 (Homogeneous elastic rods)
  • S. Saito et al. 99 (Point mass at tip Bezier
    spine)
  • B. Baxter et al. 01 (Spring-mass system)
  • Geometric Physical behaviors
  • H. Wong et al. 00 (Cone)
  • S. Xu et al. 02 (Tuft-like objects)

11
Our Brush Model
12
Our Brush Model
13
Brush Modeling
  • Layered approach
  • Brush skeleton
  • Determines dynamics
  • Brush surface
  • Determines footprint

14
Brush Modeling
  • Brush Skeleton
  • Spine
  • Connected line segments
  • For general bending
  • Lateral nodes
  • Slides along the sides of a spine node
  • For lateral deformation

15
Brush Modeling
  • Brush Surface
  • Cross-section ? two half-ellipses
  • Sweep ? along spine
  • Bristle splitting by alpha map

Tuft cross-section
16
Brush Dynamics
  • Variational approach
  • Brush skeleton of next frame obtained by energy
    minimization
  • Minimum principle for incremental displacements
  • As a constrained optimization problem
  • Objective function Total Energy deformation
    energy frictional energy
  • Constraints All nodes above paper
  • Solve using sequential quadratic programming

17
Brush Dynamics
  • Skeleton spring system

18
Brush Dynamics
  • Brush behaviors expected by real-brush users
  • Brush Plasticity
  • Wetted brush are plastic
  • Paper pore resistance
  • Small pores on paper surface
  • Fine brush tip gets trapped

19
Brush Dynamics
  • Brush Plasticity
  • Shift the spring energy function so that the zero
    (lowest) energy position is now at ?
  • ? min (?, ?),
  • ? position from last frame
  • ? max. shift

20
Brush Dynamics
  • Paper pore Resistance
  • As a moving blocking-plane constraint
  • Prevents brush tip from going towards the
    direction it is pointing
  • Adjustable lead distance

21
Summary of New Features
  • Brush flattening and spreading
  • Brush splitting at bristle level
  • Brush Plasticity
  • Paper pore resistance

22
Summary of New Features
  • Brush flattening and spreading
  • Lateral nodes
  • Brush splitting at bristle level
  • Brush Plasticity
  • Paper pore resistance

23
Summary of New Features
  • Brush flattening and spreading
  • Lateral nodes
  • Brush splitting at bristle level
  • Alpha map
  • Brush Plasticity
  • Paper pore resistance

24
Summary of New Features
  • Brush flattening and spreading
  • Lateral nodes
  • Brush splitting at bristle level
  • Alpha map
  • Brush Plasticity
  • Zero-shifting
  • Paper pore resistance

25
Summary of New Features
  • Brush flattening and spreading
  • Lateral nodes
  • Brush splitting at bristle level
  • Alpha map
  • Brush Plasticity
  • Zero-shifting
  • Paper pore resistance
  • Blocking-plane constraint

26
Video Demonstration
27
Conclusions
  • Efficient model for brush deformation
  • Plausible brush dynamics
  • Bending, flattening, spreading splitting
  • Plasticity
  • Paper pore resistance
  • Real-time on consumer-level PC
  • Oil or watercolor brushes can be modeled with
    small modifications

28
Future Work
  • Painting media modeling
  • Ink diffusion
  • Paper texture
  • Tuft hierarchy
  • Physics simulation
  • Investigate vectorial dynamics
  • User interface
  • Haptic input device
  • Stereo display

29
Thank you!
  • Questions?

? Contact cpegnel_at_ust.hk taicl_at_ust.hk
Slide show of sample output
30
Brush Dynamics
  • Observations
  • Little inertia, highly damped forces
  • Almost always in steady state
  • Vectorial approach
  • Fma, for a certain F, small m ? large a
  • Need to solve stiff differential equations ?
  • Variational approach
  • Get into next state by minimization energy
    functional
  • Minimum principle for incremental displacements

31
Brush Dynamics
Write a Comment
User Comments (0)
About PowerShow.com