## ParaView Decimate

The Decimate filter is used to simplify a triangle model by reducing the number of triangles in the model. Many times this will provide a good approximation to the original polygonal model. The filter itself uses the vtkDecimatePro filter. The input to this filter is the a vtkPolyData object.

If the input is a polygonal model (that is a model with polygons that are not triangles) then the Triangulate filter (which uses vtkTriangleFilter) must be used to create a triangle model first. Then the resulting triangle model can have the decimate filter applied to it. Otherwise, the decimation of the polygonal data set will not occur, and the output is simply equal to the input. An example of a polygonal model would be one using the Source menu to create a plane source, which is formed by quadrilaterals.

- First the user selects the data they wish to operate on from the Selection Window. It will be highlighted when this occurs.
- The user can then select
**Filter->Alphabetical->Decimate**from the main menu. This will open the Decimate filter interface. - In the
**Target Reduction**section the user can select the amount of decimation. The Reduction Target slider accepts a number between 0 and 1. This provides a target for the desired reduction of the number of triangles. A number close to 0 provides very little decimation. A number closer to 1 provides a larger reduction in the number of triangles. - The
**Feature Angle**slider is used to define edges in the model. - The
**Preserve Topology**checkbox preserves the topology of the mesh. - The
**Boundary Vertex Deletion**checkbox allows the boundary to be deleted during decimation. - The
**Apply**button must be pressed before any cutting planes or spheres will be generated. - The color attributes of the cutting plane|sphere can be changed as is detailed in the Coloring Data in ParaView Section.