Research And Implementation On Fragmentation Effect Based On Simplified Explosion Field Model

Explosion modeling is widely required by many applications of Virtual Reality, such as battlefield simulation, virtual training and so on. Explosion is a process in which physical or chemical energy is rapidly released, while it specifically refers to the chemical explosion in general. These explosions, releasing huge energy instantaneously and often giving rise to rich visible phenomena, are caused by chemical reaction of substances. The key factor for modeling explosion is to simulate these visual phenomena realistically and produce visually convincing effects. It is hard to model explosion accurately in a simple way because of its complexity. On the other hand, the accurate physics-based model is computationally expensive and it's difficult to meet real-time requirements. From the above analysis, we research on explosion modeling technology for the application of Virtual Reality and propose an algorithm to simulate the fragmentation effect of explosion. The main contributions and innovation of this thesis are summarized as follows.1. A simplified explosion field model based on diffusion process is proposed. According to the law followed by the change of velocity of explosion airflow, we abstract explosion as a process in which the gaseous product of explosion diffuses violently. Then, based on this abstraction, a diffusion model for the gaseous product's concentration is established. We develop the simplified model of the explosion field by defining velocity field of explosion airflow based on the concentration field of gaseous product.2. Based on the simplified explosion field model, we propose an algorithm to control the movement of fragments, which can simulate the actual process that explosion airflow affecting them. The algorithm captures the main features of the real movement of fragments through decomposing the movement into translation and rotation. For translation, the algorithm provides formula to calculate force exerted by the explosion airflow in simplified explosion field. For rotation, it defines the direction and speed for each fragment.3. A heuristic algorithm for rapid formation of the explosion fragments is proposed. The algorithm defines intensity of stress wave on the surface region of objects centering on the point where the blast wave hit the object first. Then, it distributes circumferential and radial cracks according to the intensity. When all cracks have been placed, it generates fragments for brittle solid objects and shell-type objects with the thickness information in a moment.4. We implement the simulation algorithm with GPU acceleration strategy. Both of the solving of simplified explosion field model and movement control algorithm has high degree of parallelism. Hence, we employ GPU to process them through designing proper kernel functions. As a result, it significantly improves the algorithm's ability to simulate large-scale problems, speeds up the simulation procedure, and saves computational resources.A number of objects are chosen to validate the efficiency our algorithm in different conditions. Experimental results show that our algorithm can achieve visually convincing result and meet real-time requirements.