Study On The Physical Model-Based Fluid Animation

In computer animation, the simulation of the fluid began in the eighties of the twentieth century. However, it is still significant and challenging. In recent years, simulating natural phemomena has always been one of the most challenging tasks in compute graphics. Simulating natural phenomena, such as hills, water, cloud, smoke, fire and so on, has been widely used in computer game, movie production and advertisement, etc. As one of its most important parts, simulating smoke, water wave and fire has been given more and more attention.Realistic animation and real-time simulation are two objectives pursued in the computer graphics applications. We aim to solve the simulation of the fluid, including simulation of smoke, water wave animation and fire animation based on the physical model by seeking for a tradeoff between the realistic effects and real time performance.The physical model used in the simulation of smoke movement is improved. Based on the improved physical model, a method for the smoke animation is proposed. The improvement on the smoke animation includes two aspects:simplifying the velocity field equations and adding the source field equation. On the one hand, we simplify the velocity field equations in the smoke animation. In the previous production of smoke animation, the full Navier-Stokes equations are generally used. In the simulation of smoke movement, the movement of smoke is modeled as non-viscous and incompressible flow. Viscous effects in the gas situation especially in coarse mesh can be ignored, and its compression can also be neglected when the fluid velocity is far below the speed of sound. On the other hand, we add the source field equation after the velocity field equations.We present a new algorithm for water wave animation based on the two-dimensional shallow water equations. Unlike traditional methods, we neither construct special functions to model the shape of water wave individually, nor solve the complex Navie-Stokes equations. Instead, the two-dimensional shallow water equations are integrated by a novel numerical method—the implicit semi-Lagrangian integration scheme—which allows large timesteps while maintaining stability. Our results show that our models and mehtods are effective and efficient. They can even satisfy the requirements of real time animation under generic PC.A physically based algorithm for fire simulation is proposed. Traditional animation technique can be helpful for virtual movement, but it is difficult for realistic movement. Compared with the traditional animation technique, physically based animation can represent realistic movement better. The full Navier-Stokes equations are used in the model, and the operator splitting method is employed to split the model into external force term, advection term, diffusion term and projection term. Every step is stable, so the whole process is also stable. Thus, the large timestep can be taken in the real-time simulation. Compared with the traditional technique, this method can be taken for realistic animation and real-time simulation of smoke in computer graphics applications.