Research Topic

Physically-Based Animation of Cutting and Fracture

Introduction

Nowadays, the use of computer-animation techniques is ubiquitous in entertainment and training applications. These are, for instance, video games [PO09], feature films [ZSL+10], surgical training and planning [WWD14], and virtual reality, to name a few. The traditional approach to animation consists in defining an object’s state at different instances in time where a smooth transition starts or ends. The actual animation is then obtained by interpolating an object’s state between the individual points in time. This technique, called key-frame animation, is often used for the animation of characters or objects with an inner source of energy.

In contrast, consider an object falling and shattering on a floor. Even so there might be only a dozen fracture pieces, it is surprisingly hard and time consuming to achieve a key-frame animation which looks realistic to a human viewer. On the one hand, the number of degrees of freedom increases very rapidly, making it quite involved to define the object’s current state. On the other hand, a viewer possesses a certain physical intuition from real-world experience with falling objects, which makes him sensitive to rather subtle details. These issues make the use of key-frame animation for passive objects or objects without an inner source of energy a rather tedious and expensive procedure, if it is not completely impractical for more complex scenarios.

Simulation and Requirements

Fortunately, the motion of passive objects is a function of initial conditions, physical equations and material parameters, thereby allowing the use of numerical methods to compute the actual animation. Clearly, this approach to animation provides an efficient and flexible way to guide or define the motion of objects, while it requires only a minimum amount of work and yields realistic results. It further allows for interactive applications which need to respond to user input, as it is the case for instance in video games and simulated virtual reality applications.

The modeling of physical objects and phenomena such as rigid and deformable bodies, thin-shells, fluids and material failure is described in a plethora of literature with a long history in mathematics, mechanics and material sciences. The primary concern in those disciplines is the accurate prediction of real-world behaviour as exact as possible. However, in computer graphics, especially in interactive applications the primary concern is to generate physically plausible behaviours with a minimum amount of computational resources. Existing methods from the discussed areas are often either not fast or stable enough to be used in computer graphics applications. This disparity in requirements shows the demand for novel methods and modeling approaches with a major concern on computational efficiency and stability.

Literature

[PO09] Parker, Eric G. and O'Brien, James F. Real-Time Deformation and Fracture in a Game Environment, Proceedings of the 2009 ACM SIGGRAPH/Eurographics Symposium on Computer Animation, SCA '09, pages 165-175, ACM, 2009

[ZSL+10] Zafar, Nafees Bin and Stephens, David and Larsson, Mårten and Sakaguchi, Ryo and Clive, Michael and Sampath, Ramprasad and Museth, Ken and Blakey, Dennis and Gazdik, Brian and Thomas, Robby. Destroying LA for "2012", ACM SIGGRAPH 2010 Talks, SIGGRAPH '10, ACM, 2010.

[WWD14] Wu, Jun and Westermann, Rüdiger and Dick, Christian. Physically-based Simulation of Cuts in Deformable Bodies: A Survey, EUROGRAPHICS 2014 State of the Art Reports, EG '14, Eurographics Association, to appear, 2014.

Research Area

Visualization and simulated reality

Contact

Sebastian Lipponer
Dipl.-Inform.

Address:

Dolivostraße 15

D-64293 Darmstadt

Germany

Phone:

+49 6151 16 - 24386

Fax:

+49 6151 16 - 24404

Office:

S4|10-207

Email:

lipponer (at) gsc.tu...

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