Game Development Reference
In-Depth Information
Figure 6. Orthogonal ellipses and best-fit ellipsoid.
After graph matching, head, torso and hand ellipses and their corresponding
attributes are sent from each processing board to the other one via the shared
memory. High-level information (ellipses corresponding to head, torso, and hand
areas) and low-level information (ellipse attributes) are used to model the best-
fit ellipsoids for each body part as shown in Figure 8. The best-fit ellipsoid
algorithm is based on Owens's (1984) work. Figure 6 displays the orthogonal
ellipses, their attributes, and best-fit ellipsoid after iterative approximation.
The equation of an ellipse is given by:
2
2
x
y
+
=
1
2
2
α
β
where
α
and
β
are the principal axes of the ellipsoid.
After rotation
φ
the ellipse equation becomes:
(
x
cos(
φ
)
+
y
sin(
φ
))
2
(
−
x
sin(
φ
)
+
y
cos(
φ
))
2
+
=
1
2
2
α
β
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