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742 Chapter 8: Modifiers
object (page 1–183). It compr ises four different
elements: t he body, the handle, the spout, and the
lid. Normally, MultiRes optimizes each discrete
element in a mesh on its own.
The default behavior of the Vertex Merging option
is to merge vertices between elements. Turning on
Within Mesh causes vertices within elements to
be merged as well.
Boundary Metric—When on, MultiRes preserves
materials assigned to the selected model. The
material boundaries defined by Material IDs are
retained as long as possible, and are the last to be
eliminated at low vertex counts. Default=off.
Maintain B ase Ver tices—When on, overrides the
MultiRes optimization algorithms and preserves
any vertices selected at the MultiRes Vertex
sub-object level as "critical" ones. Use this feature
to retain critical features of an object or character
such as its fingers or claws, or other geometry
that might b ecome unrecognizable i f reduced too
severely.
To select ver tices for use with this option, use
the MultiRes Vertex sub-object level. To access
this level, first go to the modifier stack display
and click the plus-sig n icon next to the MultiRes
modifier. This opens its hierarchy, which consists
of the single Vertex sub-object level. Next, click
the Vertex entry. T he MultiRes vertices appear on
the mesh as blue dots. You can select these using
any standard interact ive method, but you cannot
transform them.
Impor tant: After selecting MultiRes sub-obj e ct vertices
with Maintain Base Vertices turned on, regenerate the
mesh before changing the vertex resolution.
In the following illustration, the clown started out
as a high-resolution mesh. All of the MultiRes
vertices in the r ight half were selected, Maintain
Base Vert ices was turned on, and then the vertices
were reduced.
Clown model with left half reduced, right half at original
resolution
Multiple Ver tex Normals—When on, lets MultiRes
assign multiple norma ls for each vertex. By default,
MultiRes generates a sing le normal per vertex.
If multiple normals are generated, they are applied
as the vertex resolution is decreased and increased.
WhentheMultipleVertexNormalsoptionison,
the MultiRes modifier generates normal updates
when the geometry surrounding a vertex changes.
Yo u m u s t s p e c i f y a crease angle in degrees (0.0 -
180.0). The crease angle is the angle between the
face normals. It is used to decide when a normal
should be shared across an edge between two faces.
Forexample,inaplanedefinedasameshgridof
10 x 10 faces, any two adjacent faces have a c rease
angle of zero. In a cube, adjacent faces have a
crease angle of 90 degrees. In general, crease ang les
approaching 0 yield smoother shading. Crease
angles approaching 180 yield more visible corners.