MayaVi Users Guide
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# Filter Documentation

The following are the list of provided Filters along with a brief description.

CellToPointData

  This class produces PointData given an input that contains CellData. This is useful because many of VTK's algorithms work best with PointData. The filter basically wraps the vtkCellDataToPointData class.

CutPlane

  This filter takes a cut plane of any given input data set. It interpolates the attributes onto a plane. The position and orientation of the plane are configurable using a GUI.

Delaunay2D

  This filter wraps around the vtkDelaunay2D filter and lets you do 2D triangulation of a collection of points. The key parameters are Tolerance and the Alpha value. Tolerance gives the criteria for joining neighbouring data points and alpha is the threshold for the circumference of a caluculated triangulated polygon.

Delaunay3D

  This filter wraps around the vtkDelaunay3D filter and lets you do 3D triangulation of a collection of points. The key parameters are Tolerance and the Alpha value. Tolerance gives the criteria for joining neighbouring data points and alpha is the threshold for the circumference of a caluculated triangulated polygon.

ExtractGrid

  Wraps vtkExtractGrid (structured grid), vtkExtractVOI (imagedata/structured points) and vtkExtractRectilinearGrid (rectilinear grids). These filters enable one to select a portion of, or subsample an input dataset. Depending on the input data the appropriate filter is used.

ExtractTensorComponents

  This wraps the vtkExtractTensorComponents filter and allows one to select any of the nine components or the effective stress or the determinant from an input tensor data set. This will work for any dataset.

ExtractUnstructuredGrid

  This wraps the vtkExtractUnstructuredGrid filter. From the VTK docs: vtkExtractUnstructuredGrid is a general-purpose filter to extract geometry (and associated data) from an unstructured grid dataset. The extraction process is controlled by specifying a range of point ids, cell ids, or a bounding box (referred to as 'Extent'). Those cells lying within these regions are sent to the output. The user has the choice of merging coincident points (Merging is on) or using the original point set (Merging is off).

ExtractVectorComponents

  This wraps the vtkExtractVectorComponents filter and allows one to select any of the three components of an input vector data attribute.

ExtractVectorNorm

  This wraps the vtkVectorNorm filter and produces an output scalar data with the magnitude of the vector.

MaskPoints

  This wraps the vtkMaskPoints filter. The problem with this filter is that its output is Polygonal data. This means that if you add this filter to a ModuleManager with visualizations apart from HedgeHog or other velocity vector data you won't see anything! If that happens create another ModuleManager and show the other visualizations there. Also, this means that this filter should be typically inserted at the end of the list of filters.

PolyDataNormals

  This wraps the vtkPolyDataNormals filter. vtkPolyDataNormals is a filter that computes point normals for a polygonal mesh. This filter tries its best to massage the input data to a suitable form. Its output is a vtkPolyData object. Computing the normals is very useful when one wants a smoother looking surface.

StructuredPointsProbe

  A useful filter that can be used to probe any dataset using a Structured Points dataset. The filter also allows one to convert the scalar data to an unsigned short array so that the scalars can be used for volume visualization.

Threshold

  This wraps the vtkThreshold filter. The problem with this filter is that its output is an Unstructured Grid. This means that if you add this filter to a ModuleManager of a gridded dataset and you have a few grid planes, then your grid planes won't show anymore. If that happens create another ModuleManager and show the grid planes there acting on unfiltered data.

UserDefined

  This filter wraps around a user specified filter and lets one experiment with VTK filters that are not yet part of MayaVi. By default if the class is instantiated it will ask the user for the VTK class to wrap around. If passed a valid VTK class name it will try to use that particular class.

WarpScalar

  This wraps the vtkWarpScalar filter. vtkWarpScalar is a filter that modifies point coordinates by moving points along point normals by the scalar amount times the scale factor. Useful for creating carpet or x-y-z plots.

WarpVector

  Warps the geometry using the vtkWarpVector filter. vtkWarpVector is a filter that modifies point coordinates by moving points along vector times the scale factor. Useful for showing flow profiles or mechanical deformation.

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