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Book Description

Physics-based animation is commonplace in animated feature films and even special effects for live-action movies. Think about a recent movie and there will be some sort of special effects such as explosions or virtual worlds. Cloth simulation is no different and is ubiquitous because most virtual characters (hopefully!) wear some sort of clothing.

The focus of this book is physics-based cloth simulation. We start by providing background information and discuss a range of applications. This book provides explanations of multiple cloth simulation techniques. More specifically, we start with the most simple explicitly integrated mass-spring model and gradually work our way up to more complex and commonly used implicitly integrated continuum techniques in state-of-the-art implementations. We give an intuitive explanation of the techniques and give additional information on how to efficiently implement them on a computer.

This book discusses explicit and implicit integration schemes for cloth simulation modeled with mass-spring systems. In addition to this simple model, we explain the more advanced continuum-inspired cloth model introduced in the seminal work of Baraff and Witkin [1998]. This method is commonly used in industry.

We also explain recent work by Liu et al. [2013] that provides a technique to obtain fast simulations. In addition to these simulation approaches, we discuss how cloth simulations can be art directed for stylized animations based on the work of Wojtan et al. [2006]. Controllability is an essential component of a feature animation film production pipeline. We conclude by pointing the reader to more advanced techniques.

Table of Contents

  1. Preface
  2. Acknowledgments
  3. Introduction
    1. Physics-Based Animation
    2. Applications of Cloth Simulation
      1. Offline Simulations
      2. Real-Time Simulation
    3. Cloth Simulation Pipeline in Animation
      1. Research
      2. Software Development
      3. Simulation in Production
    4. History of Cloth Simulation
    5. Overview of This Book
    6. Intended Audience
    7. Getting Started
  4. Cloth Representation
    1. Triangles
    2. Particles
    3. Forces
      1. Frames and Steps
  5. Explicit Integration
    1. Introduction
    2. Explicit Integration
    3. Stability Analysis
      1. Test Equation
      2. Explicit Euler Analysis
    4. Adaptive Time Stepping
    5. Conclusion
  6. Mass-Spring Models
    1. Introduction
    2. Computing Masses
    3. Computing Forces
      1. Energy Minimization
      2. Spring Potential Energy and Force
      3. Spring Damping Force
    4. Putting It All Together
    5. Tearable Cloth
    6. Other Mass-Spring Applications
      1. Hair Simulation
      2. Soft Body Dynamics
    7. Conclusion
  7. Implicit Integration
    1. Introduction
    2. Backward Euler
      1. Linearization
    3. Stability Analysis
    4. Spring Forces and Their Derivatives
    5. Block Compressed Row Storage
      1. Matrix-Vector Multiplication
    6. Adding Velocity Constraints
    7. Solving the Linear System
      1. Preconditioning
    8. Position Alterations
    9. A Quick Note on Stability
    10. Alternative Integration Schemes
    11. Conclusion
  8. Simulation as an Optimization Problem
    1. Introduction
    2. Notation
    3. Reformulating the Problem
    4. Solving the Nonlinear Actuations
    5. Local-Global Alternation Problem Formulation
    6. Solving Time Integration Using Local-Global Alternation
      1. Local Step
      2. Global Step
    7. Conclusion
  9. Continuum Approach to Cloth
    1. Introduction
    2. Cloth Rest Shape
    3. Computing Forces and their Derivatives
      1. Damping Forces
    4. Stretch Forces (1/2)
    5. Stretch Forces (2/2)
    6. Shear Forces
    7. Bend Forces
    8. Conclusion
  10. Controlling Cloth Simulations
    1. Introduction
    2. Control Problem Formulation
      1. The Goal Function
      2. Tuning the Goal Function
      3. Minimizing the Goal Function
    3. Adjoint State Computation
    4. Updating Control Forces
    5. Creating Keyframes
    6. Conclusion
  11. Collision Detection and Response
    1. Introduction
    2. Collision Detection
      1. Bounding Volume Hierarchies
      2. Basic Primitive Tests
    3. Collision Response
      1. Cloth-Cloth Collision Response
      2. Object-Cloth Collision Response
    4. Discussion
    5. Further Reading
    6. Conclusion
  12. What's Next
    1. Real-Time Applications
    2. Subspace Cloth Simulation
    3. Alternative Cloth Models
    4. Art Directing Cloth
    5. Cloth Rendering
  13. Conclusions
  14. Vector Calculus
  15. Bibliography (1/2)
  16. Bibliography (2/2)
  17. Author's Biography
  18. Blank Page (1/3)
  19. Blank Page (2/3)
  20. Blank Page (3/3)
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