Web-based Terrain 3D Visualization Technology Research And Implementation

3D terrain is an important content of virtual scene, having widely application requirements. The paper probes into its new methods and technologies and studies on the main aspects about multi-differentiate rate, simplification and drawing. First of all, analyzing and synthesizing existing methods and techniques, we classifies and summarizes the published multi-differentiate rate models from the point view of "multi-differentiate project". Based on the "terrain simplification technology", comparing and choosing the best way for terrain model's geometric description, inducing and abstracting the result expressions, technical routes, disposed elements and means of TIN model and DEM model separately. Based on mature methods, we study and bring forward a simple arithmetic of topographic model founding on gridding vertex grads, which is a new one advanced from the simplification of visual character model. Furthermore, we research the new simplifying rules and design error measuring means based on gridding vertex grads, according to these main factors affecting visual character such as observing points, image differentiate rate and surface grads etc, and finally achieve its function by vertex eliminating technology. Experiment proved that the arithmetic can greatly simplify the terrain model in the premise of high fidelity. Aiming at multi-differentiate rate of terrain drawing, we further put forward a simplification and drawing method related to vision field, whose main idea includes that wholly simplifying terrain model by gridding vertex grids in pretreatment phrase and further modifying and measuring errors by gridding vertex encircled sphere in drawing phrase. Moreover, we analyze an approach constructed multi-differentiate rate by DEM model and design its chief arith2metic. After applying texture filled technique of matching gridding to image, the experiment outcome is finally presented. The paper systematically concludes WebGIS theory, analyzes the technical difficulties of 3D visualization based on WebGIS, and designs the technical project to realize terrain 3D visualization by Java3D in the 3-layer network frame, successfully actualizes the display and alternation of dynamic terrain modeling and 3D scence.