一种应用面积等比约束的半球面纹理映射算法

球面或半球面是两步纹理映射算法中使用较多的一种中介面。两步法中的球面纹理映射算法一般通过立体投影来实现，不可避免产生较大的纹理形变。本文首先对传统基于立体投影的球面(半球面)纹理映射算法及其不足之处进行分析，并在此基础上提出一种半球面纹理映射新算法。该算法用映射纹理区在纹理平面和半球面上的对应面积比为约束务件，显著提高了纹理映射质量。文章通过理论分析和实验对新算法与传统算法进行比较，表明新算法具有其优势，并给出几个应用新算法的两步纹理映射产生的实例，显示出本文算法对减少映射纹理变形所起的作用。

Algorithm of Hemisphere Texture Mapping Applying Constraint of Equal Ratio of Areas

Sphere or hemisphere is an important intermediary surface used in two-part texture mapping. Traditional algorithm of hemisphere texture mapping in two-part texture mapping is based on stereo-projection, where the texture distortion is unavoidable. The paper discusses the traditional algorithm and its shortcoming of texture distortion at first. And then, a new algorithm of hemisphere texture mapping is put forward, in which the ratio of areas corresponding to the mapped texture regions in the texture plane and the hemisphere is taken as the constraint. The non-distortion criteria of spherical texture mapping, which were proposed in literature [1], are better satisfied and the quality of texture mapped is improved in the new algorithm. Comparison has been made between the new algorithm and the traditional one through theory analysis and experiment results, which shows the ascendancy of the new algorithm. Some examples of texture mapping produced by the two-part texture mapping with the new algorithm are given at the end of the paper, which show the important role of the new algorithm in improving the quality of mapping texture.