ParaView Quadric Clustering
The Quadric Clustering 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 vtkQuadricClustering filter. This filter is the same one that is used to generate the level of detail in ParaView. The input to this filter is a vtkPolyData object.
The algorithm for the Quadric Clustering filter used is the one described in the paper "Out-of-Core Simplification of Large Polygonal Models" by Peter Lindstrom at SIGGRAPH 2000. The algorithm clusters vertices in a uniform binning of space. The more bins, the more accurate the representation of the original model. The fewer bins, the less accurate the representation of the original model. This filter does not preserve topology.
- 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->Quadric Clustering from the main menu. This will open the Quadric Clustering Filter interface.
- The Divisions section of the Parameter allows the user to change the number of bins in the I, J, and K direction. For more accurate representation of the original model, increase the number of bins. This will also increase the number of triangles in the final mesh.
- The Use Input Points check box selects whether to use input points in the output, or to calculate the optimal points for each bin.
- The Use Feature Edges check box selects whether to use feature edge quadrics to match up piece boundaries.
- The Use Feature Points check box feature points quadrics to match up piece boundaries.
- The Copy Cell Data check box is used to copy cell data from input to output.
- The Use Internal Triangles check box is used to toggle on/off the use of internal triangles in a bin. If it is turned off, then the computation is faster, but the output surface that is generated may be worse. If it is turned on, then the computation will be slower, but the output surface may look better.
- The Apply button must be pressed before any decimated data will be generated.
- The color attributes of the cutting plane|sphere can be changed as is detailed in the Coloring Data in ParaView Section.