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HSDS Modifier 693
HS DS M odifier
Select an object. > Modify panel > Modifier List >
Object-Space Modifiers > HSDS Modifier
Select an object. > Modifiers menu > Sub d ivision
Surfaces > HSDS Modifier
The HSDS modifier implements Hierarchical
SubDivision Surfaces. It is intended primarily as a
finishing tool rather than as a modeling tool. For
best results, perform most of your modeling using
low-polygon methods, and then use HSDS to add
detail and adaptively refine the model.
Note: Better speed optimization has b een
implemented in the HSDS modifier. Subdivision
calculations are now handled more efficiently
making the HSDS mod ifier faster.
The modifier’s pr imary features are:
•Localrefinement
• Hierarchical modeling
• Adaptive tessellation
With local refinement, you subdivide part of a
polygon mesh and edit the mesh in the subdivided
area. This is done indirectly by manipulating
sub-objects in a
control grid .Usethisfeaturewhen
you need to increase mesh resolution in specific
areas of a model rather than uniformly over the
entire object, as with the
Tessellate modifier (page
1–854)
. An example of usage would be a human
hand.Onceyou’vemodeledthebasicshape,you
might use the HSDS modifier to add bumps for
the knuckles.
TheHSDSmodifiersupportsmultiplelevels
of detail, hence its hierarchical nature. The
Subdivision Stack lets you visually navigate
the levels of detail at any time while using the
modifier. Thus, you can edit the same part of a
mesh at different mesh resolutions. If you work at
a level of detail lower t han the highest available,
the higher-detail areas are st i ll in effect, but you
controlthemindirectlybymeansofthemore
widespread sub-objects at the lower level.
Sub-object animation is supported only at
the lowest level of detail: Base Level. This is
accomplished by animating the mesh below the
HSDS modifier. To apply deformation animation
afterHSDSmodeling,firstconverttheobjecttoan
editable mesh by right-clicking the modifier stack
and choosing C ollapse All.
The adaptive tessellation automatically subdivides
polygons as needed to maintain a smoothly curved
surface when transforming mesh sub-objects. You
can use a preset or provide custom settings.
Impor tant: HSDS models are not passed up the modifier
stack. The HSDS modifi e r takes a polygon mesh as inp u t,
and outputs a triangle-based mesh.
Also, The HSDS modifier does not handle changes
to the modified object’s topology, such as altering
a sphere’s Segments setting. Topology changes to
the input mesh results i n the loss of al l edits made
in the HSDS modifier.
Procedure
To use the HSDS modifier:
1.
Apply the HSDS modifier to an object.
By default, the HSDS modifier doesn’t convert
non-quadrilateral polygons to quads. Because
the modifier works best with four-sided
polygons, it’s recommended you perform the
conversion if necessary.
2. If the object contains any non-quadrilateral
polygons,intheHSDSParametersdialog,turn
onForceQuads.ClickYesintheForceQuads?
dialog that appears.
Note: Upon conversion to quads, the modifier
automatically performs one level of subdivision
w ith smoothing (like
MeshSmooth (page
1–714)
with one iteration) on the object to