A type-merging algorithm for extracting an isosurface from volumetric data

A new approach for reducing the number of triangles representing an isosurface in volumetric data is presented. The basic idea is to classify the configurations of the marching cubes approach into types. Surface patches traversing neighboring cubes of the same type can be merged into patches, which can be approximated with fewer and larger triangles. Experimental results show that the number of triangles is about 50% of that obtained with the marching cubes algorithm, with comparable image quality. The execution time is somewhat longer than that of the marching cubes algorithm.     

Fast Isosurface Rendering on a GPU by Cell Rasterization

This paper presents a fast, high‐quality, GPU‐based isosurface rendering pipeline for implicit surfaces defined by a regular volumetric grid. GPUs are designed primarily for use with polygonal primitives, rather than volume primitives, but here we directly treat each volume cell as a single rendering primitive by designing a vertex program and fragment program on a commodity GPU. Compared with previous raycasting methods, ours has a more effective memory footprint (cache locality) and better coherence between multiple parallel SIMD processors. Furthermore, we extend and speed up our approach by introducing a new view‐dependent sorting algorithm to take advantage of the early‐z‐culling feature of the GPU to gain significant performance speed‐up. As another advantage, this sorting algorithm makes multiple transparent isosurfaces rendering available almost for free. Finally, we demonstrate the effectiveness and quality of our techniques in several real‐time rendering scenarios and include analysis and comparisons with previous work.     

Resampling Feature and Blend Regions in Polygonal Meshes for Surface Anti-Aliasing

Efficient surface reconstruction and reverse engineering techniques are usually based on a polygonal mesh representation of the geometry: the resulting models emerge from piecewise linear interpolation of a set of sample points. The quality of the reconstruction not only depends on the number and density of the sample points but also on their alignment to sharp and rounded features of the original geometry. Bad alignment can lead to severe alias artifacts. In this paper we present a sampling pattern for feature and blend regions which minimizes these alias errors. We show how to improve the quality of a given polygonal mesh model by resampling its feature and blend regions within an interactive framework. We further demonstrate sophisticated modeling operations that can be implemented based on this resampling technique.     

Real-Time Volume Deformations

Real-time free-form deformation tools are primarily based on surface or particle representations to allow for interactive modification and fast rendering of complex models. The efficient handling of volumetric representations, however, is still a challenge and has not yet been addressed sufficiently. Volumetric models, on the other hand, form an important class of representation in many applications. In this paper we present a novel approach to the real-time deformation of scalar volume data sets taking advantage of hardware supported 3D texture mapping. In a prototype implementation a modeling environment has been designed that allows for interactive manipulation of arbitrary parts of volumetric objects. In this way, any desired shape can be modeled and used subsequently in various applications. The underlying algorithms have wide applicability and can be exploited effectively for volume morphing and medical data processing.     

体数据的多精度等值面抽取

Marching Cubes（MC）算法是一个被广泛应用的体数据等值面抽取算法H本文提出的Marching Boxes（MB）算法结合显示所需精度，对MC算法作了优化，减少了由MC算法生成的三角面片数，使实时观察体数据成 为可能。在保留图象细节的前提下MB算法输出的三角面片数比MC算法减少了一半以上,从而加快了体数据的 面绘制速度.     

精确放射治疗计划系统中快速三维重建方法的研究与应用

在放射治疗计划系统中,为了精确地照射靶区避开危及器官,有必要对勾画的二维轮廓信息进行三维重建。现有的三维重建方法难以在拟合真实度和实时性上同时满足临床需求。通过对等值面提取算法进行改进,本文设计了一种快速三维重建流程,并基于可视化开发包(VTK)加以实现。多套来自真实病人影像数据的测试结果表明,快速三维重建法得到的面模型表面光滑,有效避免了"阶梯"效应;面片和顶点数目大幅度削减;与一般的等值面提取算法比较绘制时间大大减少。在保证真实拟合原始解剖结构的前提下,文中的方法改善了重建效果、提高了绘制速度,不仅可应用在精确三维放射治疗计划系统中,也可扩展应用在其他领域。     

Constructing Isosurfaces from 3D Data Sets Taking Account of Depth Sorting of Polyhedra

Creating and rendering intermediate geometric primitives is one of the approaches to visualisze data sets in 3D space.Some algorithms have been developed to construct isosurface from uniformly distributed 3D data sets.These algorithms assume that the function value varies linearly along edges of each cell.But to irregular 3D data sets,this assumption is inapplicable.Moreover,the detth sorting of cells is more complicated for irregular data sets,which is indispensable for generating isosurface images or semitransparent isosurface images,if Z-buffer method is not adopted.In this paper,isosurface models based on the assumption that the function value has nonlinear distribution within a tetrahedron are proposed.The depth sorting algorithm and data structures are developed for the irregular data sets in which cells may be subdivided into tetrahedra.The implementation issues of this algorithm are discussed and experimental results are shown to illustrate potentials of this technique.