Each time a dataset is opened from a file, a source is selected, a filter is applied, or an existing reader, source, or filter (hereafter simply referred to as filter) is selected in the Pipeline Browser, ParaView updates the Object Inspector for the corresponding output dataset. The Object Inspector has three tabs. In this chapter we are primarily concerned with the Properties tab. The Display tab gives you control over the visual characteristics of the data produced by the filter as displayed in the active view. The Information tab presents meta-information about the data produced by the filter.
From the Properties tab you modify the parameters of the filter, fine tuning what it produces from its input (if any). For example, a filter that extracts an isocontour will have a control with which to set the isovalue (or isovalues) to extract at. The specific controls and information provided on the tab then are specific to the particular vtkAlgorithm you are working with, but all filters have at least the Apply, Reset, Delete and ? (help) controls.
The help button brings up the documentation for the filter in ParaView's help system in which the input restrictions to the filter, output type generated by the filter, and descriptions of each parameter are listed. The same information is repeated in the Appendices 1, 2 of this book.
The Delete button removes this filter from the pipeline. The delete button is only enabled when there are no filters further down the pipeline that depend on this filter's output. You have to either use the Pipeline Browser and Object Inspector in conjunction to delete the dependent parts of the pipeline or use Delete All from the Edit menu.
When a reader, source, or filter is first selected, the associated data set is not immediately created. By default (unless you turn on Auto-Accept in ParaView's settings) the filter will not run until you hit the Apply button. When you do press apply, ParaView sends the values shown on the Properties tab to the data processing engine and then the pipeline is executed. This delayed commit behavior is important when working with large data, for which any given action might take a long time to finish.
Until you press Apply and any other time that the values shown on the GUI do not agree with what was last sent to the server, the the Apply button will be highlighted (in blue or green depending on your operating system). In this state the Reset button is also enabled. Pressing that returns the GUI to the last committed state, which gives you an easy way to cancel mistakes you've made before they happen.
The specific parameter control widgets vary from filter to filter and sometimes vary depending on the exact input to the filter. Some filters have no parameters at all and others have many. Many readers present the list and type of arrays in the file, and allow you to pick some or all of them as you need. In all cases the widgets shown on the Properties tab give you control over exactly what the filter does. If you are unsure of what they do, remember to hit the ? button to see the documentation for that filter.
Note that ParaView attempts to provide reasonable default settings for the parameter settings and to some extent guards against invalid entries. A numeric entry box will not let you type in non-numerical values for example. Sliders and spin boxes typically have minimum and maximum limits built in. In some cases though you may want to ignore these default limits. Whenever there is a numeric entry beside the widget, you are able to manually type in any number you need to.
Some filter parameters are best manipulated directly in the 3D View window with the mouse. For example, the Slice filter extracts slices from the data that lie on a set of parallel planes oriented in space. This type of world space interactive control is what 3D Widgets are for. The textual controls in the Properties Tab and the displayed state of the 3D widgets are always linked so that changing either updates the other. You can of course use the Reset button to revert changes you make from either place.