9.5.2

426 • CHAPTER 7
OBJECTS MENU • DEFORMERS • 427
If this option is disabled, a different method is used for co-planar areas. As an example, create a cube
with 50 segments along each side and then use Polygon Reduction on the cube, once with Co-Planar
Optimization enabled and again with it disabled. You should nd that the cube reduces considerably
faster with the option enabled.
Boundary Curve Preservation
This option attempts to preserve the original surface continuity of the object. It detects boundaries in
the original object that occur either on polygon edges that belong to only one polygon, or on polygon
edges that are shared between two polygons with a large difference in surface normals.
Surfaces enclosed by these boundaries are reduced in such a way as to preserve as closely as possible
the original boundaries, while keeping the resulting boundary and the resulting surface continuous.
However, the boundaries of differently reduced surfaces may not meet perfectly: there may be
overlaps and gaps.
For instance, consider a cylinder. This option will ensure that the cylinder wall will be continuous, and
have a continuous boundary at the top and bottom of the side walls that approximates the original
boundary. The cylinder will also retain its caps, consisting of polygons that dene a continuous
boundary that approximates the original boundary. However, the resulting wall and caps may not
meet perfectly at their boundaries.
Without this option, the polygon reduction process may introduce gaps into the boundaries when
reducing the surfaces. As a result, the resulting wall surfaces and wall boundaries will be discontinuous,
and the caps may be removed entirely.
Polygon Quality Preservation
This option, when enabled, monitors the appearance of sliver polygons (i.e. triangles with an angle
smaller than 15˚) within the object mesh during the reduction process and tries to eliminate them, if
possible. Here is an example of the appearance of sliver triangles as a result of reduction:
Enabling this option usually leads to a much better distributed mesh. On the other hand be aware that
this check will preserve any already existing sliver triangles (from the original mesh) to the highest
levels of reduction. A more thorough explanation and some advice on how to work with these options
is given in the Hints and Tips section below.