Physically-based and Real-time Simulation of Brittle Fracture for Interactive Applications. (Simulation de Fracture d'Objets Fragiles basée Physique et en Temps-Réel Pour les Applications Interactives)

In the Computer Graphics community, the animation of fracture is a key ingredient for special effects such as explosion and destruction in the movie and video game industries. Cracks are also naturally observable on aging objects like bark on trees, old roads damaged by the time and the weather. However, simulating a realistic fracture for interactive application is still challenging, especially for brittle materials that are most of the time stiff. Indeed, the fracture phenomenon intrinsically brings unique challenges on the real-time simulation of deformations due to impacts, on the collision detection algorithms, and on the evaluation and validation methods. In this manuscript, we propose new approaches to simulate efficiently realistic and real-time impact-based and age-based fracture, to handle collision detection between complex fragments, and to validate objectively and subjectively the simulations. The first contribution proposed in this manuscript is a new model of the fracture state of bodies. This model allows efficient updates to simulate crack propagations, allows efficient output of fragment surfaces for rendering, and clearly separates the model of deformation and the fracture phenomenon. We then propose a new approach based on modal analysis to simulate efficiently impact-based fracture, handling dynamic deformations of the bodies during impacts. Finally, we address aged-based fracture, allowing fast and realistic simulation of cracking bodies due to age. The second contribution deals with the interaction with fracturable bodies. We propose a new approach for the collision detection between dynamically created fragments, that allows real-time treatment of the collisions in complex scenes. The efficiency of our global system allows us to implement an haptic interaction with bodies that can fracture freely. In order to ensure the stability of the interactions, we propose a new coupling method between the simulation and haptics based on the definition of a sub-world that helps maintaining the high refresh rate imposed by this modality of interaction. Finally, we present partial validations of this work through a perceptive study, example-based fracture pattern with an optimization of fracture parameters, and fracture experiments on real objects. We also define a new metric for fracture pattern similarity based on a statistical analysis of the geometry of the fracture patterns obtained. All these contributions gathered yield a complete simulator of realistic brittle fracture, handling collision detection with complex non-convex shapes, stiff deformations during impacts, dynamic free cracks surfaces propagation at simulation rates that were not possible before.