Page 220 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes Self Assessment

Fill in the blanks:
8. In some cases there is a range of orientations that we can rotate to instead of just a
…………………….. .
9. If there is more than one center, ……………………... to any center will do.
10. Three surfaces, the elliptic and hyperbolic paraboloids and the parabolic cylinder, do not
have …………………….. .
14.3 Canonic Recognition

Canonic Recognition is a non open-source Open CASCADE component to convert, if possible, a
NURBS geometry (B-Spline/Bezier curve or surface) to its analytical form (primitive curve or
surface). The component is crucial for algorithms implemented or best fitted to work on canonic
geometry. This is especially important in CAM domain for CMM (Coordinate Measuring
Machines) and other tooling applications.
The Canonic Recognition component is based on the Open CASCADE Shape Healing module
and thereby takes advantage of its powerful capabilities.
The Canonic Recognition component includes:
1. Surfaces and curves simplification for a better reusability in downstream applications.
The NURBS conversion depends on the original geometry definition.
NURBS 3D curve can be translated to:

 Line,
 Circle or arc of circle,
 Ellipse or arc of ellipse.
NURBS surface can be translated to:
 Plane,
 Sphere,
 Cylinder,
 Cone,
 Torus.
2. The capability to merge several adjacent topological objects (edges or faces) built on
NURBS geometry into one single object based on an analytical geometry. This lowers
complexity of the topological model and makes it more usable for other algorithms and,
moreover, decreases usage of memory.
3. Tolerance management of the algorithms. The process of Canonic Recognition is handled
by user-defined tolerance which is applied for recognition and approximation with canonic
geometry.
The conversion preserves topological structure of original shape and thereby retains
connectivity of adjacent faces, edges with help of memorizing the history of modifications.
Within applications Canonic Recognition can be optimally used after importing neutral
or proprietary files (IGES, STEP, ACIS or others) or in other preparatory modules before
using special algorithms.

Task What are the basic components of canonic recognition?

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