May 20, 2011
Selecting objects by means of a rectangular frame, to trim or extend the objects inside the rectangular frame, this procedure is also called wrap processing.
Unlike performing TRIM and EXTEND commands, you don't have to indicate whether to extend or stretch while executing WRAP command, system responds to it automatically and do the corresponding operation.
Objects that are enabled to be processed by WRAP command are: lines, 2D or 3D polylines, construction lines, rays, arcs, circles, ellipse, spline polyline, wide polyline as well as splines .etc. But only under such circumstances that curve objects intersect with each other can wrap operates, except for the self-intersection of complex entities.
Nearly all of the entities are enabled wrapping as boundary objects, including blocks and xrefs.
Once you have selected objects using a rectangular frame, ZWCAD processes the objects based on their types:
For lines, construction lines, rays, arcs, circles, ellipse, spline polyline, you can both extend and trim these entities. But no processing operation implemented in case that no intersection on the selected objects or only one object is selected within the rectangular frame.
For wide polylines and 2D or 3D polylines, it's also enabled for both trim and extend. But different for that polylines can even be wrapped if only self-intersected curves are selected.
For splines, it's only enabled for trim operation, while extend is disabled.
Theory of wrap processing is determined by the following circumstances of selected object. ( the selection frame contains the whole entity being selected or only part of the selected entity ) :
Intersection for the entities by frame selection.
If the whole entity is included in the selection frame, the curve being selected by the frame is a part among the origins of source curve ( the intersection can be either on the curve or at the extension intersection. ).
If the frame only covers a part of the entity, the residual part exclusive of the part among intersections is eventually obtained after wrap processing.
Process some specific curves with particular methods, such as circle, ellipse, polyline an so on. If the entire closed circle or ellipse is selected within the frame, such objects will be taken as boundaries but not processing objects. Whereas arcs and ellipse arc have two ends which determine the wrapped curve with the relation between two points and the frame, if the two ends are not included in the frame, process them as trimming other than extending, or in case that only one end point is included in the frame, extend the curve to the far most extension intersection, and then get the curve with the same theory as getting the first point . If two points are within the frame, the curve will be extended to the nearest intersection among the two end points, and then get the wrapped curve with the same theory as treating the first point.
You should pay attention to the following matters when operating wrap processing :
It's both enabled wrap processing no matter in model space or in layout space. As manipulating trim and extend operations in different space while performing TRIM and EXTEND command.
Wrap processing is incapable of snapping entities even if the ESNAP is on, during the wrapping procedure, the ESNAP will be off temporarily and turn back to On state as soon as the wrap processing finished.
Changes for UCS take no effect on wrap processing.
Supports UNDO partially, that is to input u or ctrl + z to cancel the last manipulation but not exit the command.
EXTEND: Extends objects so as to connect to another object.
LENGTHEN: Changes object length and included angle of arcs.
PROPERTIES: Controls properties of existing objects.
TRIM: Trims object with the boundary defined by other objects.
WRAP: Frame select curves, trim or extend the curves inside the frame.
System Variables Reference
EDGEMODE: Controls the way of determining clipping edges and boundaries when performing TRIM and EXTEND command.
PROJMODE: Sets current Profile mode for trim and extend.
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