Softimage has the ability to render only a sub-set of the scene via several mechanisms: Render Selection, Track Selection and Isolate Selection.
Render Selection is active if the "SelectionOnly"context attribute is set to true, and Isolate Selection is set if the "ObjectList"context attribute is set. The selection is based only on the X3DObjects found in the selection. Sub-components and items of any other type are ignored. If no X3DObjects are found, the selection is considered empty.
In both cases, if the selection or object list is empty, then all objects are rendered.
The object list has a priority over the selection, so if both are set, the object list takes priority.
Track Selection, through the "TrackSelection"context attribute, works similarly. If an object list is present and non-empty, it uses the object list to constrain the crop window, otherwise it falls back on the current selection. If nothing is selected, no cropping is done and the entire frame is rendered.