实时仿真中的逼真虚拟地球实现

针对虚拟现实中真实感不强的问题,提出了一种具有高精度地表纹理的虚拟地球实现方法,构建了一个地表纹理像素精度高达21 600像素×10 800像素、地球表面轮廓凹凸效果和大气层光晕效果的虚拟地球.采用几何计算来构建地球形状模型,将地球按经纬度分成128块,分别计算每块区域顶点坐标、法向量、纹理坐标;采用混合纹理技术对地表纹理、云层纹理及云层法向量图进行3层纹理混合实现地球表面的云层和轮廓凹凸效果;采用实时移动与放缩带大气层纹理的正方形面板来实现大气光晕效果;采用可见性判断和纹理精度管理的方法,实时判断地球表面区域的可见性、选择不同精度纹理粘贴、剔除不可见区域,减少绘制开销.实验显示,该方法在加载1.02 GB纹理像素的情况下,达到了45帧/s的帧速率.

Realistic rendering of virtual earth in real-time application

A new approach was proposed to enhance realism of virtual earth in VR-based real-time applications. A virtual earth which had 21 600×10 800 pixels surface texture, bumping surface and shine of atmosphere was constructed.The whole virtual earth was cut into 128 parts and then the position of vertices, normal vectors, texture coordinate were calculated by geometry. Using the techniques of the mixture of the textures of earth, normal and clouds, it achieved relatively vivid surface of the earth. By moving and scaling the board which had atmosphere texture, it showed the shine of atmosphere. To achieve good real-time, it eliminated the unvisible parts by judging the parts- visibility in real-time, and chose different resolutions of texture. Experiments show that this approach is able to run 45 frames per second with 1.02GB texture pixels.