用鞍点保证拓扑正确的快速等值面提取技术

Fast iso-surface extraction method using saddle to ensure topology correct

等值面提取是研究三维数据场可视化的有效方法。针对已有的一些等值面提取算法存在的二义性问题,提出了用鞍点保证拓扑正确的快速等值面提取算法。用二线性插值和三线性插值函数来近似计算立方体表面和内部点的值,根据立方体中面鞍点和体鞍点个数的不同,将立方体剖分成不同数目的四面体。这种剖分只和原始数据的属性有关,与给定的等值无关,因此在数据不变的情况下只需要剖分一次。最后,用分层分组的方法将四面体分类到不同组中,避免在等值面提取过程中访问那些不含有等值面的四面体,从而提高了算法的速度。该算法在等值平滑变化或是随机变化时都能保持良好的特性。

Iso-surface extraction is an effective manner to study the visualization of three-dimensional data field.To solve the ambiguity question of the existing iso-surface extraction algorithms,a fast iso-surface extraction method which uses saddle to ensure the topology correct is proposed.The accurate iso-surface in the interior of cube is constructed by using the bilinear and the trilinear interpolant method.According to the number of saddle in cube,the cube is tessellated to several tetrahedral cell.This method is only relate to the properties of original data rather than the iso-value,so the cube is only tessellated once when the original data are not changed.Finally,tetrahedral cells are classified into different classes by the class group mehtod,so that only the tetrahedral cell which is intersected with the given iso-surface is visited,the speed of extration is quite improved.Whether the iso-value is smoothly changed or randomly changed,the algorithm is able to maintain a good character.