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Local Operations and Drafting

The Local Operations Component (LOP) provides a way to locally manipulate the geometry of a face or set of faces in a prescribed way without changing the topology of the solid model. LOP allows existing model features to be manipulated without the use of Boolean operations. The integrity of the model's topology and geometry remains intact as features are relocated or adjusted.

The following lists the local operation types:

Tweak
Tweaks an array of faces by calculating new geometric definitions for each edge and vertex of the tweaked faces to maintain the original ACIS body.
Move
Calculates the new face surfaces by applying a transform to the old face surfaces. Move includes sweep-more, where a face is transformed along a sweep path.
Offset
Calculates the new face surfaces by offsetting the old face surfaces by a given distance.
Taper
Includes these types: plane taper, edge taper, and shadow taper. Tapers are primarily used for modifying dies or molds to allow the work piece to be removed easily, but are also of use in general modeling.


Plane taper Calculates the new face surfaces by rotating the rulings about their intersection with the supplied taper plane. New face surfaces are defined as the envelope surfaces of cones whose apices ride along the intersection curve of the respective faces and the taper plane, whose axes are specified by the taper plane normal, and whose half-angles are equal to the supplied draft angle.

Edge taper Calculates the new face surfaces by rotating the rulings about the specified face edge curves. New face surfaces are defined as the envelope surfaces of cones whose apices ride along the respective face edge curves, whose axes are given by the supplied draft angle, and whose half-angles are equal to the supplied draft angle.

Shadow taper Uses ruled faces to remove regions where the face is considered to be "in the shadows" (face regions that have normal vectors perpendicular to the draft direction) from the specified faces.

Sheetbody extend
Extends the faces of a sheet body at the limiting edges by offsetting those edges to the specified offset distance.

LOP is not usually used through tweak, but rather through the other operations, such as moving or offsetting. These automatically create the new surfaces for a face.

Use api_initialize_local_ops to access the libraries, and api_terminate _local_ops when local operations are finished.

Local Operations and its sister components (Shelling, RBI, and Rem) all have a rich set of options which can be used to set error data and validation, order of operations, repair algorithms, and preferences for solutions. Several options are ACIS global operations, however in ACIS versions 15 and later, all Local Op APIs take the lop_options class as an argument to the API.

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