8

488 Chapter 8: Modifiers
Internally, the software "evaluates" an object
beginning at the bottom of the stack and applies
changes to the object by moving sequentially to
the top of the stack. You should therefore "read"
the sta ck from b ottom up to follow the sequence
usedbythesoftwareindisplayingorrendering
the final object.
Here is an example of stack entries for a capsule
object (an extended primitive):
• At the bottom of the stack, the first entry always
lists the object type (in this case, Capsule). You
click this entry to display the original object
creation parameters so you can adjust them. If
you haven’t applied any modifiers yet, this is the
only entry in the stack.
• Object-space modifiers appear above the object
type. You click a modifier entry to display the
modifier’s parameters so you can adjust them ,
or to delete the modifier.
Modifiers are preceded by a plus or m inus
icon if they have sub-object (or sub-modifier)
levels. See
Using the Stack at Sub-Object Level
(page 1–493)
.
• At the top of the stack are world-space modifiers
and sp ace warps bound to the object. (In the
illustration, Displace Mesh is a world-space
modifier.) These always appear at the top, and
are descr ibed as "bindings."
Basics of Using the Stack
With the stack feature, no modification has to be
permanent. By clicking an entry in the stack, you
can go back to the point w here you made that
modification. You can then rework your decisions,
temporarily turn off the modifier, or discard the
modifier entirely by deleting it. You can also insert
a new modifier in the stack at that point. The
changes you make ripple upward through the
stack, changing t he current state of the object.
Adding Multiple Modifiers
Yo u c a n a p p l y a n y nu m b e r o f m o d i f i e r s t o a n
object, including repeated applications of the same
modifier. As you start applying object modifiers
to an object, the modifiers "stack up" in the order
they’re applied. The first modifier appears just
abovetheobjecttypeatthebottomofthestack.
• The program inserts a new modifier in the stack
just above the cur rent selection, but always
in the proper location. If you try to insert a
world-space modifier between two object-space
modifiers, the program automatically places it
atthetopofthestack.
• If you select the object t ype on the st ack and
apply a new object-space modifier, it appears
just above the object type and b ecomes the first
modifier evaluated.
Effect of Stack Sequence
The software applies modifiers in their stack
order (beginning at the bottom and carrying
the cumulative change upward), so a modifier’s
location in the stack can be critical.
The following fig ure shows the difference between
the objects based entirely on a reversal in the stack
order of two modifiers. On the left-hand tube, a
Taper modifier is applied before a Bend modifier,