One or more contour values must be specified to generate the isosurfaces. This filter can stream, so that the entire volume need not be loaded at once. Streaming is controlled using the instance variable InputMemroyLimit, which has units KBytes. This filter is specialized to volumes. If you are interested in contouring other types of data, use the general vtkContourFilter .
Normal computation is failrly expensive in both time and storage.
If the output data will be processed by filters that modify topology or geometry, it may be wise to turn Normals and Gradients off. Gradient computation is fairly expensive in both time and storage. Note that if ComputeNormals is on, gradients will have to be calculated, but will not be stored in the output dataset. If the output data will be processed by filters that modify topology or geometry, it may be wise to turn Normals and Gradients off. The units of this limit is KiloBytes.