Hongxiang Ren

Development and application of distributed marine simulator

This paper introduces the main functions and technologies used in distributed full-mission marine simulator developed by Dalian Maritime University recently. As a facility for research analysis, captain training, engineering design, the simulation system has advantages of high accuracy mathematical model, low price and can display three dimension scene with 270 degree viewing field, ship dynamic image on ECDIS (Electronic Chart Display Information System) and radar image of certain sea area for training. The paper describes the main technologies used in the simulator include DIS (Distributed Interactive Simulation) technology, ship manoeuvring mathematical model, ship dynamic display based on ECDIS, Radar image, 3D scene generation using OpenGL and OpenGVS and network technology etc. The paper also introduces the application of this system in wharf design, pilot plan etc.

Real-Time Simulation and Visualization of Buoy in Irregular Wave

Buoys and other navigational aid marks are very important references to the ship’s pilots. Based on ship sea-keeping theory and the strip theory of ships in irregular waves heaving and pitching of the coupled equations of motions, we can obtain the motion mathematical model of the buoys in irregular wave. The particle system algorithm was applied to simulate the different waves of the sea level when the beacons or buoys by the impact of waves and spray occur, resulting in waves around the real-time effect, to achieve a buoy and around spray visualization, and to make visual system more realistic in the Marine Simulator.

Research on Key Technologies of Full Mission Navigation Simulation System

As an important application field of virtual reality and a typical man-in-loop simulation system, how to evaluate the performance of Full Mission Navigation Simulation System is very important. The paper presents three realism specifications to evaluate a Full Mission Navigation Simulation System: behavioural realism, environmental realism and physical realism. The three realism specifications are related with the key technologies used in the Full Mission Navigation Simulation System, which are system architecture, ship hydrodynamic mathematic model, visual system and simulated equipments. Behavioural realism is determined by ship hydrodynamic mathematic model, environmental realism is mainly determined by visual system and physical realism is determined by the simulated bridge and equipments. The paper introduces functions and requirements from three kinds of evaluation realism and key technologies in details.

Ship Fire-Fighting Training System Based on Virtual Reality Technique

The purpose of this paper is to improve the efficiency and the level of the crew fire-fighting training and save training costs. The whole framework of fire-fighting training system is designed. Fixed water fire extinguishment system, fixed carbon dioxide extinguishment system, and fire-fighting garment model are developed via the three dimension modeling technology. The action of the virtual character is simulated with the method of Inverse Kinematics (IK) applied, which reflects the imagination of the system. The nebulization of the fire and carbon dioxide is realized with utilizing particle system, enhancing the immersion of the system. The collision detection technology improving the interaction of the system is made use of to determine whether an interaction exists between virtual character and equipment, equipment and equipment, carbon dioxide and fire. The prompt information in the process of training can be provided to assist a trainee to accomplish the training. According to the experimental results, the simulation system has a favorable training effect which can be applied to ship fire-fighting training.

On the Wave Spectrum Selection in Ocean Wave Scene Simulation of the Maritime Simulator

The Phillips spectrum is widely used in the real-time scene simulation of ocean waves. Structural analysis has shown the Phillips spectrum to be an instantaneous spatial spectrum. Its frequency spectrum agrees with the spectrum form raised by Neumann, and is close to the P-M spectrum. Its directional distribution function is in the form recommended by the International Towing Tank Conference. However, the Phillips spectrum has two problems in application. First, neither the value nor the calculation method of the spectral constant A is given. Second, the height above ocean surface of the spectral wind speed is not provided. The spectral constant A is calculated on the hypothesis that the wave energy per unit area of the Phillips spectrum equals that of the P-M spectrum, and the height is specified with reference to the P-M spectrum. Apart from the Phillips spectrum, other spectrum should be considered, so we use the JONSWAP-Poisson spectrum. The spectrum has the JONSWAP spectrum as its frequency spectrum, and its distribution function is the Poisson form. The two spectra are applied for ocean wave scene simulation. A comparison of the simulation results of the two spectra shows that wind speed and fetch length can affect the shape of the generated ocean wave. The simulated ocean waves of the Phillips spectrum can reflect the wind speed and direction influence on the wave, but they cannot reflect the fetch length effect. The simulated waves of the JONSWAP-Poisson spectrum can embody the effect of the wind speed, wind direction, and fetch length on the wave. The frame rates of the two spectra are equal. To sum up, for wave spectrum selection of wave scene simulation in the maritime simulator, the wind parameter of the spectrum should contain the wind speed, wind direction, and fetch length, and the wave generated by the spectrum should be in (-(,(] of the wind direction. Thus, the JONSWAP-Poisson spectrum is more suitable than the Phillips spectrum. The method has been used in the maritime simulator.

Survey on scene simulation of the inviscid ocean wave

The scene simulation of ocean waves is a hot topic in computer graphics. Based on whether the liquid viscosity is considered, the simulation can be separated into two types, the scene simulation of viscid ocean waves and of the inviscid. For the scene simulation of viscid ocean waves, its theoretical principle is the governing equations of the viscid liquid, and it fits rendering middle and small scale size wave. When it is used for large scale rendering, the real-time ability is not good. In the scene simulation of inviscid ocean waves, the vicinity of liquid is ignored, but the simulation fits for large scale ocean waves and is real-time. The scene simulation of inviscid waves contains two methods: the method based on the regular wave and that based on the irregular. Both methods use the ocean wave spectrum. So the rendering results can reflect the wind influence on the wave. Both methods can be applied in the maritime simulator. An improvement is done by introducing a new instantaneous spatial spectrum with the JONSWAP spectrum as its frequency spectrum and the Poisson distribution as its directional distribution function. This improvement makes the generated waves show the fetch length influence. Additionally, two possible improvements for the irregular wave method are raised. One is to optimize the sampling of wave number vector to reduce the calculation amount, and the other one is to try the shallow water spectrum so that the rendered wave may reflect the water depth influence.

The Vector View-Up in Computer Graphics

In the existing textbooks on computer graphics, the vector view-up (VUP) is often used in lecturing the part of specifying the viewing coordinate system under the world coordinate system. However, the existing way of lecturing the vector VUP can not explain its actual function and exact physical meaning. The new conception of initial VUP is proposed and it is pointed out that the principle of rotating initial VUP around the vector n equals to the twist of the virtual camera. Further, for arbitrary vector VUP using initial VUP to allow it rotating twist angle around n axis, its solution method is given. Finally, the function glLookAt() of OpenGL is re-encapsulated. The scene rendering test on navigational simulator shows the proposed method is correct.