Trim Polyline

Hi,
I am looking for the best way to trim a polyline. In case of a line, it is simple. I just change the start/end point to an intersection point with the cutting object. I tried to use intersection point with the polyline, but there may be several verticies liying beyond the cutting edge that have to be removed. Just changing the start/end point to an intersection point doesn't work.
Thanks,
Mike

 

You could just create a new pline with the definition you want and delete
the old one. That is one method.

JRWalker

simple. I just change the start/end point to an intersection point with the
cutting object. I tried to use intersection point with the polyline, but
there may be several verticies liying beyond the cutting edge that have to
be removed. Just changing the start/end point to an intersection point
doesn't work.

 

Trimming polylines can be a fairly complicated exercise, and while
you can do all the work in VB, it's not something I'd savor doing.

AcadX (available at the URL below), has a Curve class that supports
a number of operations on any type of curve object (which includes
lines, arcs, polylines, splines, elliptical curves, and so on). These
include programmatic counterparts for DIVIDE, MEASURE, and
BREAK. The Curve class makes trimming these kind of objects fairly
easy using the Break() method. You get the intersection points of the
'cutting edge' and the entity that you want to trim using IntersectWith,
and then pass them to the Break() method, and it 'cuts' the entity at
the intersection points, returning an array of new objects. You can
just delete those you don't want, and that's it.

to an intersection point with the cutting object. I tried to use intersection point with the polyline, but there may be
several verticies liying beyond the cutting edge that have to be removed. Just changing the start/end point to an
intersection point doesn't work.

 

You can handle polylines by discovering in which segment you want to make the alteration. For example when using a pick routine that returns the entity and the pick point coordinate, you step through each pair of polyline vertices while checking if the pick point is on that line. There are a number of ways to do that "is on line" check. A simple function
"intWhichPolyVertice(ent,pickpoint)" that returns an interger telling you which segement number the pick point was works well as the basis for the remainder of your polyline process . It may not be the best way, but it works. I have something along these lines that I could post if you want.

AKS