9.5.2

162 • CHAPTER 6
EDIT MENU • 163
The order in which actions are processed is what we refer to as the ‘pipeline’ — actions take place one
after the other, as though they are owing through a pipe. Since the whole process determines what
is ultimately drawn on the screen, the entire concept is termed ‘the drawing pipeline’. Be aware of the
drawing pipeline so that you can predict the outcome of applying several functions simultaneously.
The Use Animations, Use Expressions, Use Generators and Use Deformers functions (see below) turn
specic elements of the drawing pipeline on or off. If an element is turned off, its data will no longer
be evaluated in the viewports. For example, if you turn off deformers, all objects will appear in their
non-deformed state.
Suppose you’ve assigned a Look At Camera tag expression to an object. You’ll
be unable to rotate the object freely in the viewport due to Use Expressions
being enabled for the drawing pipeline. (The object will continue to point at
the object with its Z-axis).
Use Animation
Animation refers to any data stored in the Timeline. Although tag expressions can animate an object,
expressions are treated as a separate data type.
Evaluation order
Tracks are evaluated from bottom to top in the Timeline, beginning with parent objects. The child
objects (sub-objects) are then evaluated according to the hierarchy; to display the hierarchy in the
Object manager, open the entire structure for a complex object group by choosing Objects > Expand
Object Group in the Object manager.
What happens if you have allocated two different position tracks (e.g. one from A to B, the other
from A to C) to the same object? The track that is top-most in the Timeline will be evaluated last of
all and will overwrite the previous movement. If track A-to-B is above track A-to-C in the Timeline,
the object will move from A to B.
Use Expressions
Expressions are evaluated from left to right as they appear in the Object manager. An expression is
a behavioral property that can be added to an object as a tag. It gives instructions to the object. An
expression could, for example, change the color used by a house material according to the state of
a sun object.