Interactive Constrained Dynamics for Rigid and Deformable Objects

Following the continuous increase in computational power of consumer hardware, interactive virtual environments have been recently enriched with more and more complex deformable objects. However, many physics engines are still very limited in the way they handle interacting rigid and deformable objects. This paper proposes a constraint-based approach to real-time simulation of coupled rigid and deformable objects capable of providing two-way interactions. Similar techniques have seen widespread usage for either rigid or deformable objects, but not for the simultaneous simulation of both. By extending such approaches, we show not only how interaction is possible but also how it can be performed at real-time rates. We address contact response and also show how to implement typical constraints to enforce limitations in the degrees of freedom and to enhance the dynamical properties of deformable objects. The method is easily integrated into existing physics engines that use similar constraint solvers and is independent on the kind of deformable object paradigm chosen. The provided simulation results show that the method is fast and effective in handling contacts between rigid and deformable objects and in simulating friction and other kinds of constraints

Graph-Based Fracture Models for Rigid Body Explosions

Explosions are one of the most powerful and devastating natural phenomena. The pressure front from the blast wave of an explosion can cause fracture of objects in its vicinity and create flying debris. In this thesis, I outline a previously proposed explosion model. An explosion is treated as a fluid with its behaviour governed by the Navier-Stokes equations and the gaseous products modeled using particles. Explosions are simulated as a means for initiating fracture of rigid bodies in the vicinity of an explosion. In contrast to fracture models that are based on physics, I propose a new approach to simulating fracture which treats fracturing the rigid body as a pre-processing step. A rigid body can be pre-fractured by treating it as graph and using one of the two proposed graph partitioning algorithms to divide the object into the desired number of pieces. By treating fracture as a pre-processing step, much less computation need be done during the simulation than models based on physics. It is shown that the recursive breadth-first search graph partitioning algorithm produces physically realistic results for shattering windows that are consistent with observations of real broken windows. The curvature-driven spectral partitioning algorithm fractures objects into two pieces where the object is weakest, where weakest is defined by the area with largest curvature. Numerical simulations of explosions and fracture were conducted to produce data that was used by a ray tracer and volume renderer to create images which were assembled into animations

Combining deformable- and rigid-body mechanics simulation

We present an interface between a deformable body mechanics model and a rigid body mechanics model. What is novel with our approach is that the physical representation in both the models is the same, which ensures behavioral correctness and allows great flexibility. We use a mass-spring representation extended with the concept of volume, and thus contact and collision. All physical interaction occurs between the mass elements only, and thus there is no need for explicit handling of rigid-deformable or rigid-rigid body interaction. This also means that bodies can be partially rigid and partially deformable. It is also possible to change whether part of a body should be rigid or not dynamically. We present a demonstration example, and also possible applications in conceptual design engineering, geometric modeling, as well as computer animation. Key words: mechanics model, deformation, collision, deformable bodies, geometric modeling, conceptual design, rigid body