Image-based meshing

Image-based meshing refers to the automated process of creating simplified user interface descriptions of three dimensions of image files without performing a previous reconstruction of the surface. Image files that have been created for example by magnetic resonance imaging ( MRI), computed tomography (CT) or X-ray microtomography, can be converted into a computer model that can be further processed, for example, in computational fluid dynamics or finite element analysis by this method.

  • 2.1 Scanning and image processing
  • 2.2 Volume and surface mesh creation

Mesh creation of a 3D image file

Creating meshes from a three-dimensional image file contains a multitude of challenges but also unique opportunities to make more realistic and more accurate geometric descriptions of the domains of definition. There are generally two methods to create a meshing of a 3D image file:

Surface -based method

The majority of the methods hitherto used traditionally work with CAD applications, as an intermediate step is inserted in which a surface reconstruction is performed, which is followed by traditional CAD-based meshing algorithms. CAD-based methods use the scan data to define the surface of the work area, and create elements within these self-defined limits. Although this robust algorithms are available, these techniques are often very time consuming and sometimes it is not possible to represent the complex structures of image data. Sometimes it is not possible to create a polygonal network of more than one domain, since multiple surfaces may produce columns and overlaps at interfaces, if a plurality of structures encountered.

Image-based method

This is a more direct method for mesh production, detection as geometric and mesh creation phases are combined in a sequence, which results in more robust and more accurate results than by meshing surface data. The meshing method most commonly used is the voxel conversion technique that generates meshes with brick elements and the Marching Cubes algorithm, which meshes with tetrahedral elements generated. A new improved volumetric marching cubes method generates four - or six -scale 3D elements by the volume of the domain and created by the mesh directly with multipart surfaces. If complex structures to be modeled with potentially hundreds of unconnected domains of definition, this approach is much simpler, more effective, more robust and more accurate.

Creation of a model

To create a 3D image -based model, the following steps are necessary:

Scanning and image processing

A variety of image processing programs can be used to obtain very accurate 3D image - based models, such as MRI, CT, MicroCT, (XMT ) and Ultrasound. May be of particular interest:

  • Segmentation (eg thresholding, level-set methods, ...)
  • Filter and smoothing (eg, volume and structure -preserving smoothing )

Volume and surface mesh creation

Image-based meshing allows direct creation of meshes from segmented 3D data. May be of particular interest:

  • Multi-part Meshing (mesh of any structures at the same time )
  • Pictures to represent material properties based on signal strength (eg modulus of elasticity or Hounsfield scale )
  • ( In order to avoid, for example, preservation of the structure of data to maintain the connectivity, and the volume shrinkage of the neutral smoothing convex sheaths ) smoothing Meshes
  • Export of FEA and CFD codes for analyzes (eg nodes, elements, material properties, contact surfaces)

Applications

  • Biomechanics and the design of medical and dental implants
  • Nutrition
  • Forensics
  • Materials science ( composite and foam )
  • Material testing
  • Paleontology and morphology
  • Reverse Engineering
  • Soil Science and Petrology
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