9.5.2

162 • CHAPTER 6
EDIT MENU • 163
Evaluation order
Expressions are evaluated from left to right as they appear in the Object manager. First the parent
object is evaluated, then the order continues along the hierarchy tree; to display this tree, open the
entire structure for a complex object group by choosing Objects > Expand Object Group in the Object
manager. The objects are evaluated from top to bottom in the order you see them.
Use Generators
Generators are objects that create temporary hierarchical structures. For example, a NURBS object
generates a temporary polygon object. You can convert the temporary object to a real object if
required using the Current State To Object command. Generators include NURBS objects, the particle
system, the array, the symmetry object, polygon primitives, spline primitives, instances, metaballs
and so on.
Evaluation order
Generators are evaluated starting with the child objects, then evaluation moves up the hierarchy
tree; to display this tree, open the entire structure for a complex object group by choosing Objects
> Expand Object Group in the Object manager. The objects are evaluated from top to bottom in the
order you see them.
Use Deformers
Deformers are the functions listed in the Objects > Deformation menu and include Explosion, FFD and
Bone. A deformer deforms the object(s) that it is applied to. The deformation is applied to a virtual
copy of the source object so that the original geometry is preserved and can always be restored. The
Polygon Reduction command also performs in this way and is therefore classed as a deformer. The
main difference between expressions and deformers is that expressions are processed before the
(virtual) copy is created, whereas deformers are processed after the copy is created.