中文摘要：

光线投射算法是最常使用的体绘制算法之一，它能够产生高质量的结果图形，但是绘制的时间复杂度高。提出了一种基于片段的光线投射算法（segment—basedraycasting，SRC），以实现加速。同许多加速技术一样，SRC利用体数据的数据一致性，但是却将优化重点放在融合阶段而不是传统的数据预处理阶段。SRC将连续的具有相似属性的重采样点合并成一个片段，然后对片段进行融合而不是对重采样点进行融合，从而减少了融合操作的次数和时间。对SRC从理论和实验两个方面进行验证。实验结果表明，软件实现的光线投射算法使用SRC后性能提高约30％，而基于GPU的光线投射算法使用SRC后性能提升的倍数与片段长度几乎相同，SRC易于与其他体绘制优化算法结合，具有较强的适用性。

英文摘要：

The traditional ray casting algorithm which is the most accurate volume rendering algorithm suffers from high computational complexity. In order to improve the traditional algorithm, a new ray casting accelerating algorithm, which is called SRC（ segment-based ray casting） for short, is proposed in this paper. There are many optimization techniques making use of data coherence to reduce process time in former researches. SRC works the same way, while the optimization is emphasized in the composition stage instead of traditional data preproeessing stage. SRC combines sequential samples which have the similar optical values into a segment. The segments substitute for the samples to be the basic composition units. Therefore, the number of composition operations is reduced. The efficiency of SRC is demonstrated by both theoretical reasoning and experiments results. The experiments results show that software SRC can improve the rendering performance by about 30% compared with traditional ray casting without degrading image quality noticeably and hardware SRC can improve the performance by nearly the same multiple as the length of the segment. In addition, SRC is easy to combine with other successful optimizations.