全球虚拟地理环境中实时阴影关键技术研究

Research on Key Technologies of Real Time Shadow in Global Virtual Geographic Environment

阴影绘制对于真实感三维虚拟地理环境具有重要意义,但目前在本领域其实现和应用仍然较少。使用阴影贴图原理在全球虚拟地理环境中绘制阴影需要解决若干关键问题。首先对全球任意位置、任意时刻的太阳光方向进行了模拟计算;然后通过紧致地形包围盒,优化了光锥视景体计算方法;最后对于全球漫游动态变化、多尺度的特点,结合级联阴影的思想,提出了一种光源视锥体动态分割算法。实验结果表明,所提出的方法能够实现高效率的全球阴影绘制。

Shadow rendering is important for realistic 3D virtual geographic environment,but there are still very few implementations and applications currently.This paper focuses on some key issues of applying shadow map to global virtual geographic environment.First the sun light direction is calculated for globally arbitrary position and time;then through the compact terrain bounding box,an optimized light frustum calculation method is proposed;finally,for the global browsing has high dynamic range and scale,we put forward a dynamic division algorithm of light frustum based on the principle of cascade shadow map.Through this research,we can achieve high efficiency shadow rendering on global virtual environment.