vtkAssembly - create hierarchies of actors

Super Class: vtkActor

Description:

vtkAssembly is an object that groups actors and other assemblies into a tree-like hierarchy. The actors and assemblies can then be transformed together by transforming just the root assembly of the hierarchy. A vtkAssembly object can be used in place of an vtkActor since it is a subclass of vtkActor. The difference is that vtkAssembly maintains a list of actor instances (its "parts") that form the assembly. Then, any operation that modifies the parent assembly will modify all its parts. Note that this process is recursive: you can create groups consisting of assemblies and/or actors to arbitrary depth. Actor's (or assemblies) that compose an assembly need not be added to a renderer's list of actors, as long as the parent assembly is in the list of actors. This is because they are automatically renderered during the hierarchical traversal process. Since a vtkAssembly object is a derived class of vtkActor, it has properties and possibly a mapper. During the rendering process, if a mapper is associated with the assembly, it is rendered with these properties. Otherwise, the properties have no effect (i.e., on the children of the assembly).

Caveats:

Collections of assemblies are slower to render than an equivalent list of actors. This is because to support arbitrary nesting of assemblies, the state of the assemblies (i.e., transformation matrices) must be propagated through the assembly hierarchy. Assemblies can consist of hierarchies of assemblies, where one actor or assembly used in one hierarchy is also used in other hierarchies. However, make that there are no cycles (e.g., parent->child->parent), this will cause program failure.

See Also:

vtkActor vtkTransform vtkMapper vtkPolyDataMapper

Methods:

Detailed Method Descriptions: