9

934 Glossary
See also
IK Goal (page 3–954)
Envelopes
In Physique (page 2–1076),theenvelopeisthe
primary tool for controlling skin deformation. An
envelope defines an area of influence about a single
link in the hierarchy. If the envelope is deformable
(page 3–927), mesh vert ices within that e nvelope
follow the movement of the Physique deformation
spline (page 3–927). An envelope has a p air of
inner and outer bounds; the env elope’s influence is
strongest at the inner bound, and falls off toward
the outer bound. By default, each envelope has
four cross sections. You can reshape the cross
sections, or add new ones, to change the envelope’s
geometry.
In the Skin modifier (page 1–791),theenvelope
plays a similar role with respect to bones. Each
bone has its own envelope with two or more
cross-sections that allow you to shape the envelope
to fit the surrounding mesh.
Typically, the envelopes of adjacent links or bones
overlap each other. Vertices that fall in the overlap
area are weighted to produce smooth blending at
joint intersect ions.
Envir onment Ma p
Above: Image uses a picture in screen coordinates as a
background.
Below: Image shows spherical mapping coordinates applied
using a checker map.
Texture coordinates lock a m ap to geometry.
Environment coordinates, on the other hand, lock
a map to the world. If you move t he object, the
map remains in place. If you move the view (or
camera), the map changes. This ty pe of mapping
system is used with reflection, refract ion, and
environment maps.
There are four types of environment coordinates:
•Spherical
•Cylindrical
•Shrink-Wrap
•Screen
Thefirstthreearethesameasthoseusedbythe
UVW Map modifier (page 1–922).Ifyouimagine
a sphere, infinite in size, surrounding your scene
and mapped with spherical mapping coordinates,