Some Useful Definitions
closed contours: Contours that do not have start and end points, such as circles, rectangles, and closed polygons. Infinite contours, such as lines, are also closed.
contours: Shapes that are continuous paths in the plane. Contours may be drawn with a single stroke of a pen without lifting the pen or retracing. Most primitive shapes are contours.
handedness: Non-intersecting, closed contours are either right handed or left handed. Handedness determines the direction in which points are generated when the curve is sampled.
hierarchical refinement: Hierarchical refinement of a shape hierarchy preserves the structure of the original hierarchy up to the leaf nodes. The leaf nodes may themselves be expanded into full hierarchies in the refinement.
hole regions: Regions that are children of solid regions in a region tree.
Non-Uniform Rational B-Splines (NURBs): Another name for the CVL implementation of de Boor splines. De Boor spline control points have associated positive scalar weights. Increasing the weight of any control point pulls the spline curve toward that point; decreasing the weight reduces the effect of that point on the curve.
open contours: Continous curves with well-defined start and end points, which may coincide, through which they can be connected to other open contours. Examples of open contours are line segments, elliptical arcs, and open polygons.
perimeter positions: Arbitrary and unique points along CVL shapes. Perimeter ranges can be used to delineate arbitrary sections of a shape.
perimeter ranges: Pairings of a perimeter position and a signed distance that delineate arbitrary sections of a shape
phantom holes: Holes at the root of a region tree used to group disjoint solid regions into a single region tree.
primitive shapes: Shapes that are not made up of a shape tree, such as a line segment or a circle.
regions: Shapes that partition the plane into an inside and an outside. The inside has a finite area and extent. The outside is the complement of the inside.
shape hierarchy: A drawing usually comprises a shape hierarchy consisting of several component shapes. See also shape tree.
shape information objects: Objects that encapsulate detailed information about specific shapes. This information is required for the perimeter and parameterization functions.
shape tree: A composition of shapes organized in an hierarchical fashion, starting with a root node and ending at the leaf nodes. CVL has specialized shape tree classes to contain contour shapes and region shapes, and a general shape tree to contain any kind of shape.
solid regions: Regions that are children of hole regions in a region tree.
wireframes: Type of generalized polygon used to implement a synthetic model. To use a wireframe shape with PatMax, you must put the wireframe into a shape tree prior to training.