Modeling And Rendering For Physical-based Ocean Wave In Navigation Scene

The simulation of ocean wave is an important part of fluid simulation.Its realism,rapidity and interactivity directly affect the fidelity of navigation scenes.Traditional methods have some shortcomings,such as inability to simulate realistic bow waves,splashes on the sea surface,fluid-solid interaction,and so on.The physical simulation method based on computational fluid dynamics has become the main means to improve the realistic effect.Smoothed Particle Hydrodynamics(SPH)is suitable for treating free surfaces and capturing spray splashing and foam.Five key points of SPH method,namely GPU acceleration,fluid-solid coupling,incompressibility of water,surface reconstruction of fluid,foam and spray,are studied in depth.Considering the requirements of realistic rendering of waves,spray,foam and ship-wave coupling,this paper presents a method of modeling and rendering ocean waves based on SPH.The CPU-GPU hybrid architecture for SPH fluid computation is proposed.The whole physical simulation process is implemented on GPU,especially the GPU parallel neighborhood search algorithm.Through the simulation results,convergence analysis and performance test of typical scenarios,it is verified that GPU algorithm for physical modeling of ocean waves in navigation scene greatly improves the overall simulation efficiency compared with CPU algorithm.In order to solve the complex boundary problem of fluid-solid coupling in navigation scene,a new boundary handling method based on repulsive force is proposed.The unified particle model is employed and the solid surface are sampled into boundary particles,which are involved in physical calculation.The continuity equation and momentum equation are improved and applied to simulate fluid-solid interaction in navigation scenes.The effectiveness of the algorithm is verified by the simulation of navigation scenes such as the interaction of waves with lighthouses,life buoys and container ships.The fluid-solid interaction algorithm can deal with complex boundary problems.The algorithm satisfies momentum conservation and non-penetration conditions,and can simulate the interaction between fluid with solid boundary and rigid body.Aiming at the problem of low efficiency of incompressibility in navigation scene,an incompressible fluid simulation method based on relaxed density invariance is proposed.Through the predictive-corrective iteration method,the ratio of pressure to density square can be directly solved,and the density of fluid particles near the boundary is corrected,and relaxation method and optimization of initial value selection are adopted to accelerate convergence.While satisfying the stability,it does not need to frequently perform time-consuming neighborhood search.The proposed method achieves better performance than PCISPH method and improves the execution efficiency.Only the condition of constant density cannot satisfy mass conservation,but also the divergence-free velocity field is needed.Therefore,an incompressible fluid simulation method based on divergence-free condition is further proposed.Two pressure solvers with constant density and divergence-free velocity are combined and integrated into the fluid simulation.A relaxation method is also used to accelerate the convergence.Compared with PBF method,the method can maintain the velocity-divergence-free,improve the accuracy,and ensure the stability of the system at a larger time step.The simulation results,convergence analysis and performance tests of typical experiments verify the effectiveness and stability of the proposed incompressible fluid simulation algorithm.Foam and spray are the most typical visual characteristics of rolling wave in navigation scene.In the paper,a unified particle modeling method for foam and spray is presented.the diffused particles are used to model the foam and spray splashing,and the possibility of generating diffused particles according to the geometric characteristics,kinetic energy and relative velocity of fluid particles is determined.The simulation of the advection and dissipation of foam and spay.Aiming at the problem of surface reconstruction of fluid,the rendering method of screen space was optimized.Experiments show that the method increases the effect of detail scale such as similar to surface tension,foam and spray,and realizes the simulation of small-scale navigation scene.