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    • Segmentation
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    • Worked Example: 3D Slicer (Lung)
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  • Home
  • Printing Techniques
  • Design Considerations
    • General
    • Ultimaker
    • FormLabs
  • CAD Software
    • Onshape >
      • Basics
      • Sketching
      • Constraints
      • Extrude
      • Revolve
      • Fillet & Chamfer
      • Shell & Draft
      • Direct Editing
    • FreeCAD >
      • Turner's Cube
      • Whiffle Ball
      • Casino Dice
      • Bearing Bracket
      • Fork Bearing
      • Compression Spring
      • Propeller
      • Inner Threads
      • Outer Threads
      • Heart Shaped Ashtray
      • Bird Feeder
      • Ball Bearing
  • Image to STL
    • Medical Images
    • Segmentation
    • Refinement
    • Worked Example: 3D Slicer (Lung)
    • Worked Example: Seg3D (Rib)
    • Completed Examples >
      • Ribs
      • Kidney
      • Brain
  • STL to Print
    • Cura (Ultimaker)
    • Preform (Formlabs)

Image to STL: Mesh Refinement

Introduction

​•Following segmentation, the 3D model can be further refined into a polished, printable piece
​
•Basic refinement involves removing artefacts from the segmentation process and repairing errors

•The anatomically accurate model can then be incorporated into a finished 3D print model, which may include additional structures.
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Example Refinement Techniques

The number of potential operations one might perform on a raw .stl file from a segmentation are too numerous for an exhaustive list. Computer aided design tools allow almost limitless mesh manipulation and refinement. However there are a few processes that most models will go through:
Repairing
• Errors and discontinuities can sometimes arise in the segmentation & exporting process, need to be repaired before printing

Smoothing
• Staircasing errors resulting from the resolution of the original medical image can be mitigated by smoothing the surface of the mesh model

Appending
• The segmentation will often only be one component of a final model. To convert the model into a final, useable form it is often necessary to combine it with other structures to, or subtracting volumes from, the mesh. 
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Refinement Software

There is a huge range of software that will allow greater or lesser degrees of mesh refinement. Powerful, professional software will often have the most comprehensive set of utilities. When using freely available software, it is often necessary to use several different packages in combination in order to leverage the unique advantages of each. Here are a few examples of useful, free software that provide essential mesh refinement tools
FreeCAD: http://www.freecadweb.org/
• Open source computer-aided design software. Limited functionality, but very easy to use and useful for viewing and designing models
• Check out our tutorial page

NetFabb Basic: http://www.netfabb.com/basic.php
• Free version of professional NetFabb software, with a very useful mesh repair tool.
• If nothing else, we recommend checking all models in NetFabb before printing.

Blender: https://www.blender.org/
• Primarily a rendering and animation software. However it has some very useful tools for performing Boolean operations on large meshes

​MeshMixer: http://www.meshmixer.com/
• Very useful mesh viewing and manipulation software.
• Easy to use, with several essential mesh refinement tools
• Used extensively in the Seg3D & 3D Slicer worked examples. 

MeshLAB: http://meshlab.sourceforge.net/
• Less intuitive user interface, but has a selection of powerful functionalities that are difficult to find freely elsewhere

CAD Inventor: http://www.autodesk.co.uk/products/inventor/overview
• Powerful, professional 3D design software that students often have free access to through their institutions. 

Next Stage...

Worked example: Seg3d
Worked Example: slicer

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