China
Africa
Explore chapters and articles related to this topic
Image-Based Triangular and Tetrahedral Meshing
Published in Yongjie Jessica Zhang, Geometric Modeling and Mesh Generation from Scanned Images, 2018
In scanned images such as CT and MRI, the geometric surface often exists implicitly as an isosurface or a level set. Although there have been tremendous progresses in geometric modeling and mesh generation, high-fidelity mesh generation directly from images is still a challenging problem. The volumetric imaging data V can be written as a scalar field sampled on rectilinear grids, that is, V = {f (i,j,k) | i,j, k are indices of x,y,z coordinates in a rectilinear grid}. Within a cubic cell or voxel, we can construct a trilinear function to define a continuous field in it.
Data Representation
Published in Alexandru Telea, Data Visualization, 2014
As we shall see next, the value (or luminance) component of an HSV color is equal to the maximum of the R, G, and B components. Hence, all colors shown by an HSV color wheel for a given value V ∈ [0, 1] are equivalent to all points on the outer faces of a cube similar to the whole RGB cube but of edge size V. Such an equal-value surface for V = 0.5 is shown in Figure 3.14 inside the RGB cube. As we shall see in Section 5.3, such a constant-value surface is called an isosurface.
C
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
contour (1) an image curve, often used to represent the set of points where a given function has a given constant value. A familiar example is a contour line on a topographic map. Here the contour denotes where the land has a given elevation. Another type of map contour might denote the boundary between increasing and decreasing population density. The equivalent concept in 3D is the level surface or isosurface.
Controllable three-dimension auxetic structure design strategies based on triply periodic minimal surfaces and the application in hip implant
Published in Virtual and Physical Prototyping, 2023
Bo Liu, Jiawei Feng, Zhiwei Lin, Yong He, Jianzhong Fu
TPMS is a type of minimal surface with zero mean curvature, where the surface areas are minimised under the assigned boundaries. TPMS surfaces are of many types. This research involves P surface and G surface, and their functional formulas are as follows: Schwarz P Gyroid where and c are periodic and threshold parameters, respectively. As an iso-surface, TPMS can be generated and drawn using visualisation algorithms. As the most widely adopted 3D visualisation method, the marching cubes (MC) algorithm can efficiently extract any iso-surface within a defined 3D data field (Lorensen and Cline 1987). The MC method divides space into a 3D discrete data field. In the data field, the iso-surface is approximated by linear interpolation. The meshes divided by linear interpolation can be used for rendering and manufacturing.
3D visualization modeling of nonwoven fabrics from multi-focus images
Published in The Journal of The Textile Institute, 2022
Yan He, Na Deng, Binjie Xin, Lulu Liu
Marching cubes algorithm is also known as the isosurface extraction method. In the 3 D data field, voxels are constructed with a certain unit volume. In the condition of the given threshold, the isosurface of each voxel is extracted, and the isosurface is drawn through the isopoint coordinates and normal vector of the triangular patch to complete the reconstruction of the object (Cirne & Pedrini, 2013; Johansson & Carr, 2006). The isosurface extraction method retains the gray information inside the object and can reflect the spatial structure of the object more realistically, and the details of the reconstructed contour are clear. For the reconstruction of the microscopic images, the clarity of the outline details is a very important index, and the true reflection of the spatial structure of the object can reflect the significance of microscopic reconstruction in the research. Therefore, this paper uses the Marching cubes algorithm to reconstruct the nonwoven fiber region extracted from the optical slice.
Integration of cortical thickness data in a statistical shape model of the scapula
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Jonathan Pitocchi, Roel Wirix-Speetjens, G. Harry van Lenthe, María Ángeles Pérez
An algorithm was developed in Python 3.5 to automatically estimate sampled cortical thickness (Figure 1) starting from the initial three-dimensional model. For each point in the model surface, HU values were sampled along the line passing through that point and perpendicular to the surface, with a sampled distance of 0.1 mm. As a result, a HU profile was obtained for each point in the surface. First, a threshold of 226 HU was applied to detect the cortical bone in the profile and separate cortical and trabecular values. The full-width at half maximum method (FWHM) was used to estimate the cortical thickness by setting the 10th percentile of the trabecular intensities as the value for the trabecular bone. Using a Variable Wrapped Offset algorithm, it was possible to build the inner surface (representing the trabecular bone) by setting the measured cortical thickness as local offset for each point of the outer surface. The algorithm makes use of a vtkContourFilter to generate the Isosurface mesh from the scalar values (VTK: vtkContourFilter Class Reference).