8

802 Chapter 8: Modifiers
Pressure Af fects—
Selects the brush parameter to
be affected by pressure sensitivity. Choose from
four options: None, Strength, Size, or both size
and strength (Size/Str).
Predef ined S tr Pr ess ure—Tur n th is opt ion on to u se
a predefined strength pressure. Click the button to
view and edit t he falloff curve for the st rength .
Predef ined S ize Pres sur e—Tur n this opt ion on to
use a predefined size pressure. Click the button to
v iew and edit the fal loff curve for the size.
Mirror group
Mirror—Turn this option on to mirror the paint
gizmo on the other side of the object. Choose an
axis from the drop-down menu. The paint g izmo
is mirrored about the selected axis in the world
coordinate system.
Offset—Offsetsthemirrorplanebythevalueyou
specify.
Gizmo S ize—Changes the mirror gizmo size to a
value you specify.
Misc group
Tree Depth—Determines the size of the quad tree
used for hit testing. Tree Depth relates to the
amount of memory set aside for weight painting.
Larger values mean faster interaction but more
memory use.
Update On M ouse Up—Prevents the system from
updating viewports when the mouse button is
pressed. This can save time in your workflow.
Lag R ate—Deter m ines how often the stroke
updates the painted surface. Higher values update
the surface less often.
Sk in Morph Modifier
The Skin Morph modifier lets you use a bone ’s
rotation to drive a morph; that is, a deformation
of the object mesh. Skin Morph is intended for
use with a Skin or comparable modifier (e.g.,
Physique); add the Skin Morph modifier after
the skin-t ype modifier. You create the morph at
the frame in w h ich the effect should be greatest,
and then Skin Morph automatically animates the
affected vertices into and out of the morph, based
on the rotation of the bone that drives the morph.
This lets you fine-tune mesh deformation at any
frame, using a bone to d rive the mor ph that is
fixingaproblemarea.Typically,whenanimatinga
character with bones, an artist has to create extra
bonestohandleproblemareassuchasarmpitsand
groin areas. With Skin Morph, instead of using
extra bones, you can simply create a morph, and
then transform vertices into the exact shape you
want. Skin Morph lets you easily create muscle
bulges and many other effects.
Note: When working with Skin Morph, it’s
important to be familiar with the concept of
delta .Theframeatwhichyouapplythemodifier
determines the base position for each ver tex that’s
used in a morphing animation controlled by Skin
Morph. After applying the modifier, go to a frame
at which the bone driving the morph is rotated an
amount that will cause the greatest deformation,
and then transform vertices to produce the morph.
Theamountbywhichyoutransformthevertices
is called the
delta : the difference between t he base
poseandthemorphedposition.
Procedure
To use S k in Mor ph (ba sic usage):
1.
Create an animated character with bones and
a skinned bo dy mesh, using a modifier such as
Skin (page 1–781) or Physique (page 2–692) .
2. Go to the “pose frame” and apply the Skin
Morph modifier.
Theposeframecontainstheinitialpose;
typically a standing charac ter with arms
outstretched and legs apar t. This is often