Research On Soil Erosion Prediction And Virtual Reality Landscape In Small Watershed Of Loess Plateau

Loess Plateau as one of the severest soil erosion regions in the world, the serious soil erosion of those caused many negative problems, such as degradation of soil physical properties, soil nutrient loss, vegetation degraded, ecology fragiled, economy developed slowly etc. Meanwhile, sand sedimentation in the lower river made aggravation of flood disaster. Therefore, our country pays great attention to it and takes many effective measures to conduct soil and water conservation ecological building in the Loess Plateau, but situation of soil erosion is still severe.Soil erosion prediction in small watershed was implemented based on BP network in this paper. In addition, explored theory and key technology of visualization, discussed primarily realization of realistic three-dimension landscape. And a system of soil erosion prediction and virtual reality landscape in small watershed with was built. The main research and results as follows:(1) Improved learn algorithm of BP network, chose average annual rainfall, rainfall to make flood, annual runoff and runoff to make flood as input variables, soil erosion of small watershed as output variable. According to observation data in many years, a network was built and trained, and tested the precision result, which gained better forecasting accuracy.(2) Discussed the constructing three-dimension terrain based on contour line. In order to solve the problem of continuity in illumination model and enhance the reality, a weighted average method to compute the normal vector at grid vertex was proposed in this paper. A sky-ball model was built for background of sky, which combined with texture mapping technology and clock control, realized the scene of moving clouds.(3) A"crossing method"based on image was designed in drawing virtual trees, which had batter visual image quality and fast rendering ability.(4) Studied on simulation of natural rainfall with particle system, selected position, lift period and shape as attributes of particle. What's more, designed a linked list data structure to generate new particles, calculate move of particles, draw particles and delete dead particles in turn.(5) The surface runoff of small watershed was a complex physical process, to realize its virtual reality, a geologic model of the flow direction was simplified, and flow direction was determined by eight-grid algorithm. For lowland, to solve the problem of continuity in runoff, a new method of increasing their elevation value gradually was put forward. The results obtained a fairly satisfactory simulating effect based on particle system.