Image-based meshing is the automated process of creating computer models for

computational fluid dynamics Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid dynamics, fluid flows. Computers are used to perform the calculations required ...

(CFD) and

finite element analysis Finite element method (FEM) is a popular method for numerically solving differential equations arising in engineering and mathematical models, mathematical modeling. Typical problem areas of interest include the traditional fields of structural ...

(FEA) from 3D image data (such as

magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...

(MRI),

computed tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...

(CT) or

microtomography In radiography, X-ray microtomography uses X-rays to create cross-sections of a physical object that can be used to recreate a virtual model (3D modeling, 3D model) without destroying the original object. It is similar to tomography and X-ray c ...

). Although a wide range of

mesh generation Mesh generation is the practice of creating a polygon mesh, mesh, a subdivision of a continuous geometric space into discrete geometric and topological cells. Often these cells form a simplicial complex. Usually the cells partition the geometric ...

techniques are currently available, these were usually developed to generate models from

computer-aided design Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...

(CAD), and therefore have difficulties meshing from 3D imaging data.

Mesh generation from 3D imaging data

Meshing from 3D imaging data presents a number of challenges but also unique opportunities for presenting a more realistic and accurate geometrical description of the computational domain. There are generally two ways of meshing from 3D imaging data:

CAD-based approach

The majority of approaches used to date still follow the traditional CAD route by using an intermediary step of surface reconstruction which is then followed by a traditional CAD-based meshing algorithm. CAD-based approaches use the scan data to define the surface of the domain and then create elements within this defined boundary. Although reasonably robust algorithms are now available, these techniques are often time consuming, and virtually intractable for the complex topologies typical of image data. They also do not easily allow for more than one domain to be meshed, as multiple surfaces are often non-conforming with gaps or overlaps at interfaces where one or more structures meet.

Image-based approach

This approach is the more direct way as it combines the geometric detection and mesh creation stages in one process which offers a more robust and accurate result than meshing from surface data. Voxel conversion technique providing meshes with brick elements and with tetrahedral elements have been proposed. Another approach generates 3D tetrahedral or tetrahedral elements throughout the volume of the domain, thus creating the mesh directly with conforming multipart surfaces. Young et al, 2008. An efficient approach to converting 3D image data into highly accurate computational models. ''Philosophical Transactions of the Royal Society A'', 366, 3155–3173.

Generating a model

The steps involved in the generation of models based on 3D imaging data are:

Scan and image processing

An extensive range of

image processing An image or picture is a visual representation. An image can be two-dimensional, such as a drawing, painting, or photograph, or three-dimensional, such as a carving or sculpture. Images may be displayed through other media, including a pr ...

tools can be used to generate highly accurate models based on data from 3D imaging modalities, e.g. MRI, CT, MicroCT (XMT), and Ultrasound. Features of particular interest include: * Segmentation tools (e.g. thresholding, floodfill, level set methods, etc.) * Filters and smoothing tools (e.g. volume- and topology-preserving smoothing and noise reduction/artefact removing).

Volume and surface mesh generation

The image-based meshing technique allows the straightforward generation of meshes out of segmented 3D data. Features of particular interest include: * Multi-part meshing (mesh any number of structures simultaneously) * Mapping functions to apply material properties based on signal strength (e.g.

Young's modulus Young's modulus (or the Young modulus) is a mechanical property of solid materials that measures the tensile or compressive stiffness when the force is applied lengthwise. It is the modulus of elasticity for tension or axial compression. Youn ...

Hounsfield scale The Hounsfield scale ( ), named after Sir Godfrey Hounsfield, is a quantitative scale for describing radiodensity. It is frequently used in CT scans, where its value is also termed CT number. Definition The Hounsfield unit (HU) scale is a linear t ...

) * Smoothing of meshes (e.g. topological preservation of data to ensure preservation of connectivity, and volume neutral smoothing to prevent shrinkage of convex hulls) * Export to FEA and CFD codes for analysis (e.g. node sets, shell elements, material properties, contact surfaces, boundary layers, inlets/outlets)

Typical use

Biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...

and design of medical and dental implants *

Food science Food science (or bromatology) is the basic science and applied science of food; its scope starts at overlap with agricultural science and nutritional science and leads through the scientific aspects of food safety and food processing, informing ...

Forensic science Forensic science combines principles of law and science to investigate criminal activity. Through crime scene investigations and laboratory analysis, forensic scientists are able to link suspects to evidence. An example is determining the time and ...

Materials science Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials sci ...

(composites and foams) *

Nondestructive testing Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), n ...

(NDT) *

Paleontology Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure ge ...

and

functional morphology Functional may refer to: * Movements in architecture: ** Functionalism (architecture) ** Form follows function * Functional group, combination of atoms within molecules * Medical conditions without currently visible organic basis: ** Functional ...

Reverse engineering Reverse engineering (also known as backwards engineering or back engineering) is a process or method through which one attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accompl ...

Soil science Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, soil classification, classification and Soil survey, mapping; Soil physics, physical, Soil chemistry, chemical, Soil biology, biologica ...

Petrophysics Petrophysics (from the Greek πέτρα, ''petra'', "rock" and φύσις, '' physis'', "nature") is the study of physical and chemical rock properties and their interactions with fluids. A major application of petrophysics is in studying reserv ...

References

External links

Computing-Objects
commercial C++ libraries for mesh generation & FEM computation * ScanIP commercial image-based meshing software
www.simpleware.com
* Mimics 3D image-based engineering software for FEA and CFD on anatomical data
Mimics website
* Google group on image-based modelling

* Avizo (software), Avizo Software's 3D image-based meshing tools for CFD and FEA * iso2mesh: a free 3D surface and volumetric mesh generator for matlab/octav

OOF3D
object oriented finite element analysis from the

NIST The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

VGSTUDIO MAX
Commercial CT analysis software for industry. They offer an add-on module for FEM meshing. {{DEFAULTSORT:Image-Based Meshing Mesh generation Computer graphics algorithms 3D computer graphics