8
480 Chapter 8: Modifiers
An object can carry any number of modifiers, but
it always has only a single set of transforms.
The transforms of an object are expressed as
a matrix of values that contain the following
information:
• Position of the object center in world space
• Rotation of the object in world space
• Scale of the object along its local axes
The matrix is cal led the
transformation matrix
,
and its information relates directly to the
transforms Move, Rotate, and Scale. Applying
one of these transforms alters the values in the
transformation matrix.
Transforms have the following properties. They
are:
• Appliedtotheentireobject.
• Independent of their order of application. No
matterhowmanytimesyoutransforman
object, the results are stored as one set of values
in the matrix.
• Applied af ter all object-sp ace modifiers have
been evaluated, but before the world-space
modifiers. S ee
Using the Modifier Stack (page
1–487)
.
Most transforms produce equal displacement
along one or more axes of an object, or part
of an object. For
Move (page 1–419)
,
Rotate
(page 1–420)
,and
Uniform Scale (page 1–421)
transforms, the displacement is equal along all
threeaxes.Whenyourotateabox,allsidesremain
parallel. In general, all vertices keep the same
relative position to one another. The exceptions
are
Squash (page 1–422)
and
Non-Uniform Scale
(page 1–421)
, which displace axes by different
amounts.
Tip: Use the
XForm modifier (page 1–942)
if you
wanttotransformanobjectataspecificlocation
in the stack (that is, after some object-space
modifiers but b efore others), or if you want to
transform a sub-object selection. See
Modifying at
the Sub-Object Level (page 1–492)
.
Modifiers
Most modifiers allow you to perform operations
on the internal str uc ture of an object in
object
space (page 3–1076)
.Forexample,whenyou
apply a modifier such as
Twist (page 1–865)
to
a mesh object, the position of each vertex of the
object is changed in object space to produce the
tw isting effect.
Modifiers can operate at the sub-object level, and
are dependent on the internal structure of the
object when the modifier is applied.
Modifiers have the follow ing properties. They are:
• Applied to al l of an object or p art of an object
(using a sub-object selection).
• Dependent on the order of application.
ApplyingaBendfollowedbyaTwistproducesa
result different from applying a Twist followed
by a Bend.
• Displayed as individual entries in the modifier
stack,whereyoucanturnthemonoroff,and
change the order in which they’re applied.
Some modifiers operate in world space. These
use world-space coordinates, and are applied to
the object af ter all object-space modifiers and
transforms have been applied. Otherwise, they
havethesameoverallpropertiesasobject-space
modifiers.
Tr ansforms, Modif iers, and Object
Dat a Flow
Once you have defined an object, 3ds Max
evaluates changes affecting the base object and
displays the result in the scene. What these changes
are, and the order in which they are evaluated, is
called the
object data flow
.