Sets the scalar type of the region. The region should not be allocated yet. If the data of this region is not going to be set explicitely, this method can be used to make a new data object for the region. Extent, and ScalarType should be set before this method is called. You can set the data object explicitly.
Old data is released, and the region automatically registers the new data.
This assumes that the Data being set has already been allocated. This method is used mainly by vtkImageCache . If one does not exist, the a data object is created. This method returns the memory that would be required to fill the region. The returned value is in units KBytes.