Research And Implementation Of Input 3D Terrain Technology Based On Image

Terrain is one of the most complex objects in the nature.Terrain visualization has become increasingly in recent years because it has wide application backgrounds, it is a subject about the display,simplification,simulation of Digital Terrain Mode or Digital Height Field.It is part of computer graphics.The techniques of generation and visualization for three -dimensional terrain are both important tools for many realms and interesting research field in Computer Graphics.The paper analyzed the source of the 3D terrain data.Because the grey scale image and contour image is easy to be obtained,the data input technology base on the image is raised.The system provide interface,the user only need simple operation such as input the data.The system read the 3D terrain data from the 2D terrain image and read it into interactive 3D terrain building system based on visual sense,then 3D terrain is built.In this paper,the fundamental theory and methods of terrain modeling, include regular square grid and triangulated irregular network,is studied. Then ,commprehensively summarize the previous work.The key point is regular square grid.In the view of the input data defect of the original system,the paper provide two input data method base on the 2D terrain image. One is base on the bitmap,this way is light of the mapping between gray levels of the bitmap and the height of the terrain.In other words,the minimum gray point is the lowest terrain and the maximum gray point is the summit.The other is based on contor line.The way is that first editing the contour line,then saving these heights,finally depending on linear calculating middle value,thus getting the height of every mesh point,and read the 3D terrain data into VRML file of the original system. The most important question is how to realize the input 3D terrain data technology base on contour picture. According to the character of contour, the paper introduce the method of autotracking the contour which can autotrack the point of the contour without thinning it beforhand. We use the linear interpolation method to fill the geomorphic information between the contours.The paper introduce detailded method of the input 3D terrain,the method is easy and has little demand of the computer and it is applicable to generate 3D terrain of small scale.