基于微机环境的三维数据场多等值面快速显示算法

MICRO-COMPUTER BASED MULTI-ISOSURFACES RENDERING ALGORITHM FOR 3D DATA SETS

直接体绘制技术能够利用半透明效果显示三维数据场，提供了比等值面绘制方法更为丰富的信息．但是，由于数据场中所有体素都参与了图象生成过程，使得该技术的计算开销昂贵，远远无法达到交互式操作的要求．事实上，如果用边界表示法来表示三维数据场，就可以利用三维空间连续性来大幅度缩短绘制时间．边界表示法只关心有等值面穿过的边界体元，用Ｏ（ｋｎ２）内存单元来表示Ｏ（ｎ３）大小的原始数据场，从而产生大规模数据压缩．本文在此基础上提出一种基于微机环境的显示算法，生成图象效果近似于直接体绘制技术，而速度至少提高一个数量级．文章还给出了用新算法绘制的三维医学图象，并与ｒａｙｃａｓｔｉｎｇ算法的结果在图象质量和绘制时间上做了比较．

Direct volume rendering techniques use semi-transparency to visualize much more important features in the three-dimensional scalar sample volumes than isosurface rendering methods. However, since all voxels participate in the generation of each image,these techniques are computationally expensive and far from interactive manipulation. In fact, on the base of the boundary representation scheme for the volumetric data, the 3D spatial coherence can be fully exploited to drastically reduce the rendering time for arbitrary viewing orientation. This data model only considers the bounding cells pierced by theisosurfaces of specified materials ; therefore, it requires O(kn2) memory cells to represent O(n3) volumetric data, and produces a high degree of data compression. A PC-based rendering algorithm in use of the boundary scheme is proposed in this paper, which producesresults visually similar to the volume rendering techniques, but speedup at least an order of magnitude. Examples from medical CT studies are given in contrast to the results from ray casting method both in image quality and in processing time.