Isosurface Generation Using VTK




VTK Basics



3.2. Filter Objects


Filter objects take one or more input objects and generate one or more output objects.  In this tutorial, filter objects play a variety of roles.  An object named vtkExtractVOI will obtain the region of interest from a very large data file in the tens of megabytes.  Afterwards, the image data will need to be isolated further by selecting a particular isosurface with either vtkContourFilter or vtkMarchingCubes.  In the following sections, each class will be presented with a general description, followed by a listing of all relevant functions and their respective purposes, and finally, there will be a chance to test out each of the classes on the data file that will be used for the tutorial and working off practice code generated from 3.1.


With respect to the last section, the beginnings of a VTK pipeline are starting to form.  vtkExtractVOI takes the output from vtkImageReader2 and sets it as the input for vtkExtractVOI.  Remember, the above description is how a pipeline is created— get the output from one object and set the output as input to another class.  From there, the output from vtkExtractVOI will serve as input to either vtkContourFilter or vtkMarchingCubes since only one of these two filters can be used.  Below is a diagram of the pipeline created so far that helps to illustrate this idea.





 +-- vtkExtractVOI


      +-- vtkMarchingCubes


      +-- vtkContourFilter


Figure 3.1: VTK pipeline for using vtkExtractVOI and vtkMatchingCubes or vtkContourFilter



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