Entities from which the boundary is created

My drawing consists of only lines and curves. Command boundary returns a polyline or a region. I am trying to figure out what entities actually formed this boundary. In other words, I pick a point on the drawing, and need to get the handles of all the lines/curves on my drawing that participated in boundary creation. It would be great to get a VB analog of the AutoCAD "boundary" command, or at least an algorythm of how this can be done.

 

Well, you could iterate through all items in the drawing and do an IntersectsWith against your new boundary entity.

Regards

Wayne Ivory
IT Analyst Programmer
Wespine Industries Pty Ltd

 

Well, if a line intersects the boundary, that doesn't necessarily mean that it forms it. Besides, the boundary command itself takes a lot of time to run. If I add a function that iterates through all the entities in the drawing, it would take forever. I would like to avoid that if possible.

 

I can't actually think of a situation where a line intersects the boundary but doesn't form part of it. Even if it T-junctions on the outside it still has a small component in the boundary, although I can understand that you might not want that one. I think you could check the number of intersections in that case and where it is only one perhaps discount it.

As for the iteration performance, it depends on the number of entities we're talking about, but an alternative might be doing a selection set 'Crossing' the boundary. Depending on your requirements you may have to subsequently exclude fully-contained items from the set (search this group for methods for determining if a point is inside a polyline, especially with the use of rays).

Regards

Wayne

 

Scratch the point-inside-polyline idea - a better way would be to iterate the selection set and do an IntersectWith on each item. If it doesn't intersect then it is fully-contained within the boundary.

Regards

Wayne

 

How about lines that are parallel, therefore don't intersect?

 

I don't understand what you're asking about parallel lines. They wouldn't be part of the boundary and they wouldn't be picked up by the method I've suggested.

Perhaps you can explain your question a bit more.

Regards

Wayne

 

I am sorry, Wayne. My last question had nothing to do with the task. I guess I was thinking about something else.

I still have a little complication, though. All the entities that I am looking for are on xrefs. Do I have to copy them onto the modelspace one by one, then intersect, then delete, or is there another way?

 

Not sure, sorry. I don't do any work with xrefs. Perhaps somebody else can help?

Regards

Wayne