topic Rubberbanding a polyline arc in ObjectARX Forum

Rubberbanding a polyline arc

Anonymous — Fri, 16 May 2008 00:05:41 GMT

I am trying to display a rubberband when a user creates a 2d arc polyline. If I use the pline command, I can see the shape that the arc will be when the user selects the second point. I want to mimic this with ObjectARX and the acedGetPoint command.

Currently I can see the straight rubberband that connects the first point to the second point, but not what the 2d arc will look like.

I searched these forums for 'Rubberband' and came up with 5 topics. I found that I might be able to use a jig, but I think that might be overkill...

Is there an easier way to show the arc without using a jig?

Re: Rubberbanding a polyline arc

Anonymous — Fri, 16 May 2008 02:34:08 GMT

It's either a jig, or AcEdInputPointMonitor.

--
http://www.caddzone.com

AcadXTabs: MDI Document Tabs for AutoCAD 2009
Supporting AutoCAD 2000 through 2009

http://www.acadxtabs.com

Introducing AcadXTabs 2010:
http://www.caddzone.com/acadxtabs/AcadXTabs2010.htm

wrote in message news:5932746@discussion.autodesk.com...
I am trying to display a rubberband when a user creates a 2d arc polyline. If I use the pline command, I can see the shape that the arc will be when the user selects the second point. I want to mimic this with ObjectARX and the acedGetPoint command.

Currently I can see the straight rubberband that connects the first point to the second point, but not what the 2d arc will look like.

I searched these forums for 'Rubberband' and came up with 5 topics. I found that I might be able to use a jig, but I think that might be overkill...

Is there an easier way to show the arc without using a jig?

Re: Rubberbanding a polyline arc

Anonymous — Fri, 16 May 2008 22:25:53 GMT

Thanks for the reply Tony... I decided to implement the jig approach because I have already done something with the AcEdInputMonitor and want to learn something new.

Here is my current problem... I have modified the ObjectARX sample db_elipsJig (or something like that) and I have 're-created' what I already have. I can select the start point and I get a rubberband to the end point, but no arc in between the two points. (or an arc with a bulge of 0.0)

Maybe some context would help... When you create a 2 point Arc with the ACad drawing tools, you get a straight rubberband between the two end points as well as an arc rubberband that represents the arc. If I create a 2 pt arc in ObjectARX then there is no indicator for the user as to what the arc will look like. (The 2 point arc can be somewhat chaotic for someone not used to them.) So I'm trying to make 2 point arc creation more useful for the user.

I've looked at the Arc datatypes and none of them appear to be the 2 point type... At least not that I can make out. I thought I might be able to 'fake' an arc and then save the polyline with an arc.

So... I can put a bulge in there, but I don't know how the pline command calculates the bulge for a 2 point arc.

So... I guess the question is, "How do I calculate the bulge between two points so that the final arc between the two points matches what autocad would draw with the pline command for the same two points?

I'm sorry for being so verbose. As someone famous once said, "I could have made it shorter if I had more time." (Or something like that...)

Thanks.