PHYSICALLY-BASED SIMULATION OF LIQUIDS IN INTERACTIVE ENVIRONMENTS
Dr. Ahmad Khalaf
Department of Electrical, faculty of Engineering, lraqi University, Iraq.
Matter in the liquid state of aggregation is referred to as a liquid. The physical behaviour of liquids is discussed within the framework of the fluid mechanics described. The numerical and most accurate simulation possible of the flow behaviour of liquids is an important part of the research and Development. Because of the complex dynamics of liquids, However, such physical simulations are too computationally intensive for interactive applications, such as virtual reality environments or computer games.
The general motion of fluids (gases and Newtonian liquids) is physically described by the Navier-Stokes equations. The Navier-Stokes equations can be formulated in a compressible and an incompressible form. Change of the volume of substance under external pressure, this property is called compressibility. Vice versa incompressibility denotes the property when under external pressure no volume change occurs. Real materials are always compressible.
On a macroscopic level, however, gases are classified as compressible and liquids and solids are generally considered incompressible because of the degree of compression is so small that it can often be neglected. For this reason, only the incompressible Navier-Stokes equations are considered in this work.It should be mentioned that the incompressible consideration is not the representation of effects that result from density fluctuations. For example, the representation of sound propagation or extreme temperature gradientsnot possible with the incompressible representation. such effects however, are of secondary importance in computer graphics[6, 7].
The performance improvements of standard PC hardware have exceeded the ambitions of research on liquid representation on these systems also towards interactive or real-time presentation. It is designated that real-time systems as computing systems whose processing results are available within a specified period of time. Computer graphics adapt existing physical simulation methods, to realize realistic animations of virtual liquids. The aim of this efforts is an automatic, realistic, and plausible dynamic and representation. To achieve comparable realism with classic animation techniques, it is normally associated with a great deal of time and effort. In real-time environments, where the user interacts with the environment, there is no significant alternative to simulations since the interaction is unpredictable. Usually approximating physical simulation methods with classic animation methods are combined, so that for the simulation methods in computer graphics in term of physically-based method is used. Despite the use of physics-based simulation techniques for the animation of liquids require generation Photo-realistic results. However, it takes many minutes or hours per image (e.g. [9, 10]). Because in addition to the simulation, there is one constantly changing surface of the liquid and optical depict characteristics to extract realistically. These three steps are computationally expensive.