The Research About The Algorithm Of Physically-based Large Scale Fluid Simulation

The physically-based fluid simulation technology has attracted more and more attention from many graphics researchers during recent years. It has significant research and application value not only in computer games, feature films but also in virtual reality areas and so on.To achieve an accurate, real-time and physically-based fluid simulator is the goal of this area. However, it is hard to satisfy the accuracy and the real-time simultaneously. To find a suitable real time fluid simulation method, we first give a sample of using an eulerian method to simulate gas, which illustrates that the eulerian method is not suitable for large-scale real time fluid simulation. So we adopt SPH methods and some of its extension to implement a real-time fluid simulation frame on GPU. Also, in combination with a screen space based rendering method, we accomplish the real time simulation and rendering of 3D water and multiphase flow.When using SPH methods for fluid simulation, we use Tait equations to satisfy the incompressibility of fluid. There is tensile instability problem in standard SPH methods. We use a simple density correction method to solve this problem in this paper. However, one side effect of eliminating tensile instability is lower cohesion between the particles, which makes the surface tension of fluid disappear. So after density correction, we introduce an artificial tension item to simulate surface tension phenomenon.For boundary collision, we simultaneously adopt two ways: based on penalty force and sample ghost particles in the border. Also, comparing with two experiments, we conclude that the way of sampling the ghost particles is superior to the way of penalty force in terms of collision detection and collision response.For multiphase flow, we simulate it using a SPH method which is modified by numerical density. We find that using this way causes a problem: some parts gather low density of particles so that these low density particles will not float on the high density particles eventually. We bring in an artificial buoyancy to settle the problem. We adopt a rendering way based on screen space to render the final fluid. This way uses the ideas of curvature flow to smooth the surface depth and then calculate the surface normal based on the depth information after smooth. Meanwhile, the method uses an additional pass to get information about the thickness of the fluid, which is as an important basis of fluid color.