Prev | Up | Next

# Generating Contours (Isosurfaces)

The contour filter is used to generate isosurfaces and isolines from scalar values in a data set. If the VTK library a particular version of ParaView is using includes the patented classes, contouring is done with the vtkKitwareContourFilter. Otherwise vtkContourFilter is used. Regardless, the interface to contouring within ParaView is the same.

First the user must select which point data array to use to generate contours. When the array is selected, the data range of that array is displayed in the user interface. Then any number of contour values can be entered. The contour values desired should be entered in the "New Value" entry box. The value can be entered into the list of contour values either by pressing the "Enter" key or by clicking the "Add Value" button. In order to remove a value from the list, click on the value and then click the "Delete Value" button.

The user must also decide whether to have normals, gradients, and scalars computed for the isosurfaces or isolines generated by the contour filter. (Note: Selecting "Compute Normals" or "Compute Gradients" will have no effect if the vtkContourFilter -- as opposed to the vtkKitwareContourFilter -- is used.) Computation of normals is fairly expensive (in terms of both time and storage) as is computation of gradients. Especially if further filtering is to be done on the isosurfaces or isolines, it may be wise to turn off computation of gradients and normals. If scalars are computed, then for each point in a particular isocontour, the corresponding contour value will be stored. Typically scalars are computed when contours are generated.

Prev | Up | Next

Last modified: Mon Dec 3 13:21:01 EST 2001