Figure 2 provides an overview of the editing operation
for changing the depth of a vertex. Figure 2(a) shows that the
vertex is moved from its initial (depth) position to the next
(depth) position in the cross-sectional plane by dragging the
mouse. The cross-sectional plane is called the “depth control
plane.”. Next, by moving the cross-sectional plane back and
forth, the user can move the vertex in the cross-sectional
plane to adjust the depth position. This means that the depth
of the vertex can be changed by varying the position of the
cross-sectional plane. Figure 2(b) shows how the vertex can
be moved in the cross-sectional plane by dragging the mouse.
If a user drags the mouse over the vertex on the 2D display,
the vertex of the 3DCG object is moved in the depth control
plane