9.5.2

164 • CHAPTER 6
EDIT MENU • 165
Evaluation order
Deformers 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.
The following example claries why the evaluation order for deformers and generators begins with
child objects. A Loft NURBS creates a temporary polygon object — it is a generator. Suppose the
splines that describe the Loft NURBS are themselves deformed by several FFD objects (deformers). The
hierarchy tree might look as in the illustration below.
It’s only possible for the FFDs (sub-objects of the splines) to deform the splines before they are used
by the NURBS object if the evaluation order is from the bottom of the hierarchy tree to the top.
The display order
We have addressed the order in which elements of the same data type are evaluated, but what is the
evaluation order for elements of differing types? Again, the display pipeline works to a strict order:
 First, all animation data is evaluated.
 Next, the expressions are evaluated (provided that you’ve not changed their
priority).
 Finally, and with top priority, the generators and deformers are evaluated.