Game Development Reference
In-Depth Information
Figure 11. The fields of the SBBone (a) and SBMuscle (b) node.
(a)
(b)
identifier, their geometric transformations have the same set of parameter
values.
The bone-skin influence volume described is implemented as follows: the
specification of the affected vertices and the measure of affectedness are
obtained by instantiating the
skinCoordIndex
and
skinCoordWeight
fields.
The
skinCoordIndex
field enumerates the indices of all skin vertices affected
by the current bone. The
skinCoordWeight
field is a list of values of affected-
ness measure (one for each vertex listed in
skinCoordIndex
). The influence
volume specified with respect to a certain number of planes (discretisation step)
is computed as follows. The
sectionInner
(respectively,
sectionOuter
) field is
a list of inner (respectively, outer) radii of the influence volume corresponding
to different planes. The
sectionPosition
field corresponds to the distance
d
. The
falloff
field specifies the choice of the measure of affectedness function as
π
sin(
x
)
follows: -1 for
x
3
, 0 for
x
2
, 1 for
x
, 2 for
, 3 for
x
and 4 for
3
x
. The
2
location of the bone is specified by the
center
and
endpoint
fields.
The possible 3D geometric transformation consists of (in this order): (1)
(optionally) a non-uniform scale; (2) a rotation with respect to an arbitrary point
and axis; and (3) a translation. The transformation is obtained through the fields
rotation
,
translation
,
scale
and
scaleOrientation
. The global geometric
transformation of a given child of a bone is obtained by composing the bone
transformation of the child with the parent. The
rotationOrder
field contains
information related to the conversion from the quaternion representation, used
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