Graphics Reference
In-Depth Information
If you try the snapping functionality at this point by moving the geometry in the active layer, you will no-
tice that the Move tool simply stops at intervals, when elements in the foreground layer are within snapping
range of elements in the background layer. The geometry does not, however, deform based on the back-
ground geometry.
To achieve the kind of deformation necessary for this purpose, you need to engage a constraint. Unlike
simple snapping, a constraint (in this case, a background constraint) physically restricts the movements of
geometric data on a vertex basis. As a result, when a background constraint is enabled, you can deform
foreground geometry based on the geometry in the background layer. As with the Snapping mode, when a
constraint is enabled, additional options appear. The Constrain To Background section enables you to set
an offset (the distance between snapped geometry and existing background geometry), to constrain handles
of curve objects to the geometry (Handle Constraint), and to snap to both sides of single-sided polygons
(Double Sided).
With the background constraint enabled, you can now use the Push tool to constrain the rounded square
to the background pedestal. There is, however, one main difficulty when using this type of tool to create a
clothlike effect—and that is topology. Because the polygons are flowing up and down and left and right on
the cloth mesh, and diagonally on the pedestal, it will be difficult to get good corners and edges when wrap-
ping the cloth around the background geometry (see
Figure 5-16
)
. To deal with this issue, you can take two
steps for a more natural appearance: first, rearrange the topology of the cloth, and second, create a closely
adhering top panel by using existing geometry.
Figure 5-16:
The misalignment of foreground and background topology
