基于层次多项式纹理的实时草地绘制

根据草的几何结构复杂性和材质的漫反射特性,提出层次多项式纹理(layered polynomial texture,简称LPT)来表示草,可以高效真实地实现这个目标.LPT是一个五维纹理,每一个纹理单元是一组多项式系数,记录分布在多层像素的不同光照方向下亮度的拟合信息,用于在绘制时计算出纹理像素的颜色.把草表示成3个沿已知视线方向的LPT,然后基于Wang Tile的LPT合成方法生成拼图块,再映射到地面上得到草地,从而获得动态光照环境下草地的实时绘制.实验结果表明,LPT的存储量小,运算代价低,而且LPT能推广到树的表示,也可以实现树的动态阴影效果.

Layered Polynomial Textures for Real-Time Grassland Rendering

This paper presents a layered polynomial texture (LPT) to represent grass based on its complex geometric structure and diffuses material. LPT is a 5D texture, and its element contains a group of polynomial parameters, to fit the pixels of multiple layers with various lighting directions, and to calculate the actual color in rendering stage. Grass is represented with three LPTs along known view directions. The LPT synthesis method based on wang tile is presented to create tiles, which are mapped onto ground to form grassland. The grassland is rendered in the dynamic lighting condition. Experimental results show that the LPT storage is smaller, and computational cost is lower. Furthermore, LPT could be extended to represent trees with dynamic shadow.