AutoCAD 2007/2008/2009

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Active Contributor
Posts: 38
Registered: ‎05-23-2003
Message 1 of 12 (6,067 Views)

Has Autocad figured out how to explode ellipses?

6067 Views, 11 Replies
03-18-2009 11:00 AM
I know about the Flatten command and that's better than nothing, but has Autocad ever figured out how to explode an ellipse into the basic 4 arc segments that they are made of instead of exploding to a spline? I know you can get crazy with ellipses, but they are a pain to work with - especially with editing. I just had to lay out seating in a stadium setting with an elliptical plan - in 3D. :smileysad:

To get the most exact trace of an ellipse that I can use (usually for arraying/trimming commands), I've deivided the ellipse segment using nodes and then tracing using PLINE with the Second Point command. It's accurate enough to edit and modify, but it creates LOTS of snap points (END and MID). When someone else has to work on the file, they get lazy and if they need to recreate or modify the ellipse segment, they shortcut the trace and it just gets progressively worse.
*Dean Saadallah
Message 2 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 11:25 AM in reply to: JeroldL
Splines have not changed.

--
Dean Saadallah
http://LTisACAD.blogspot.com
--
Distinguished Contributor
philip
Posts: 307
Registered: ‎04-07-2005
Message 3 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 12:19 PM in reply to: JeroldL
Hi it might not be what you are wanting
but set PELLIPSE to 1
now when you draw an ellipse it will be a polyline which can be exploded to form arcs.
setting PELLIPSE to 0 resets back to spline
*Matt Kolberg
Message 4 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 12:40 PM in reply to: JeroldL
I don't believe he was asking about a spline. He wants to explode an
ellipse.

--
Matt Kolberg
Global CADD Systems
www.gcscorp.ca


"Dean Saadallah" wrote in message
news:6144518@discussion.autodesk.com...
Splines have not changed.

--
Dean Saadallah
http://LTisACAD.blogspot.com
--
*Dean Saadallah
Message 5 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 01:24 PM in reply to: JeroldL
Ellipse are drawn as Splines by default... . Splines behavior has not
changed in AutoCAD, Flatten is the only fix.

--
Dean Saadallah
http://LTisACAD.blogspot.com
--
*Matt Kolberg
Message 6 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 01:28 PM in reply to: JeroldL
My ellipses are drawn as an "Ellipse" if PELLIPSE is set to 0.
They are drawn as a splined polyline if PELLIPSE is set to 1.

Neither are splines. Flatten does not work with an "ellipse" object.


--
Matt Kolberg
Global CADD Systems
www.gcscorp.ca


"Dean Saadallah" wrote in message
news:6144654@discussion.autodesk.com...
Ellipse are drawn as Splines by default... . Splines behavior has not
changed in AutoCAD, Flatten is the only fix.

--
Dean Saadallah
http://LTisACAD.blogspot.com
--
*Bill Gilliss
Message 7 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 01:39 PM in reply to: JeroldL

JeroldL wrote:
...
has Autocad ever figured out how to explode an ellipse into the basic 4
arc segments that they are made of ...

-

-

Ellipses are not made up of four basic arc segments. I (and
you) apparently learned how to approximate an ellipse on the boards
with a couple of constructed tangential arcs, but an ellipse's
curvature varies continuously, whereas that of an arc is fixed.
Entirely different animal down at the nano level.



As Phillip suggested, the quickest way to get a polyline of arc
segments is to set PELLIPSE = 1, and just trace the ellipse osnapping
to QUAdrant, which picks up the end points of the major and minor axes.



However, accuracy suffers: on a 100' long x 50' wide ellipse, the
polyline version varied from the true ellipse by up to 1.25". If your
anchor bolts locations depended on this, there might be trouble.



For more accuracy, I offset the ellipse a known distance, thus creating
a spline, and then offset the spline back the same distance. This gives
me a variance of only 0.01" or so. I then used ToolPac's Convert >
Splines > To Polylines function to convert the spline to a polyline
with arc segments every 24" inches, and the resulting polyline differed
from the original true ellipse by no more than 0.0005". Pretty amazing.



As someone wrote in another context, whatever you want, you can have it
good or fast or cheap -- pick any two.



-Bill

Distinguished Contributor
Posts: 497
Registered: ‎01-25-2006
Message 8 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 01:39 PM in reply to: JeroldL
You could draw the ellipse using the pre-cad hand drafting methods based on your major/minor axis and then you would end up with arcs.
*Jason Piercey
Message 9 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 02:22 PM in reply to: JeroldL
Since when?

"Dean Saadallah" wrote in message
news:6144654@discussion.autodesk.com...
> Ellipse are drawn as Splines by default... .
Active Contributor
Posts: 38
Registered: ‎05-23-2003
Message 10 of 12 (6,067 Views)

Re: Has Autocad figured out how to explode ellipses?

03-18-2009 02:50 PM in reply to: JeroldL
Thanks.

I like the Pellipse setting. It's better than nothing.

Where can I get the ToolPac's Convert software? I'd like to give it a try...

My office does a lot of masterplanning, so a lot of it gets fasttracked.
I had to whip out some manuals on how to build them by hand and build it that way in 2009 so I could break it down to editable arcs.

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