纹理映射技术中正方形过滤器边长的计算方法

纹理映射技术是通过纹理过滤实现的,由于实时的面过滤方式计算消耗比较大,实际应用中常采用正方形过滤器进行预过滤(如Mipmap技术)。在实时显示时,如果把象素近似看作一个正方形,其在纹理空间投影的区域通常是一个不规则的曲边四边形,常用一个正方形来近似表示。通过这个正方形过滤器的边长d与预过滤使用的正方形过滤器的边长D 进行比较,查找预过滤的标准采样表进行过滤计算,但是对不规则曲面四边形采用多大的正方形来近似不好确定。本研究以Mipmap技术为例分析了预过滤的原理和常用d 值的求取办法,提出了一个采用四边形对角线求取近似正方形边长d 的方法,并在理论上进行了讨论。

Study on the Method of Computing of Side-Length of Square Filter in Texture Mapping Technique

Texture mapping technique is realized by texture filtering. In practice,square filter is usually adapted to prefilter due to Real-time surface-filtering being high consumptive(e.g. Mipmap technique). The projection of pixel on texture space generally is an irregular quadrangle if it is regarded as a square in Real-time presenting. The irregular quadrangle is commonly approximately showed by the square. Looking up standard sample table with after refiltering by comparing side length d of the square with D of the square filter, but it is not easy of computing the side length d of the square to approximate to the irregular quadrangle. In this paper,we analyzes the principle of pre-filtration and ways of evaluation in common use of d with example Mipmap, and a method for computing the side length d of approximate square via diagonal of quadrangle is offered. The discussion on the efficiency of the method in theory is cluded.