Draw a parabola

Farid · 7th Nov 2009, 09:15 pm

I am working on vertical alignment of highways and need to draw draw a vertical, which is a parabola, in AutoCAD 2010. Anyone can help me.

ReMark · 7th Nov 2009, 10:35 pm

What information do you have to work with? Can you share it with us?

CarlB · 7th Nov 2009, 11:15 pm

Discussed in this thread, with link to an earlier thread.
http://www.cadtutor.net/forum/showthread.php?t=28775

"Vertical curves are parabolas, you can draw them by drawing a polyline from endpoint to VPI to endpoint, then PEDIT>>Spline. For it to be a proper parabola, set SPLINETYPE to 5 before pediting, and to get a smooth curve set SPLINESEGS to 15 or higher. (Thanks to rc McSwain for the Spline/parabola info)."

Farid · 7th Nov 2009, 11:35 pm

i have the equation of the parabola, and I know the begging point of the curve, the vertex, and the end point of the curve. It will be very helpful if I can plot the equation. I tried the polyline, and then changed it to spline. But changes it's positing and became smaller.

CarlB · 7th Nov 2009, 11:47 pm

If by "vertex" you mean the high or low point of the curve, then yes the curve will be inaccurate after "pedit". it should be initially drawn as two straight segments, from start curve, VPI (intersection of tangents) (VPT) to end of curve.

if you want to plot the curve, you can do the calculations in Excel, with x & y values in adjacent columns; start the pline command, copy & paste values from Excel

Farid · 8th Nov 2009, 12:07 am

yes, exactly. I mean VPI by vertex. If plot that in excel, then I think I won't be able export to AutoCAD so that I continue the further on based on what I exported. It will be only a raster image.

SEANT · 8th Nov 2009, 01:32 am

To expand a bit on the procedure described by CarlB: If the parabola is symmetrical, i.e., the two end points are horizontal and the vertex is above the middle of those two points, then the poly’s 2nd point should be at twice the height of the desired vertex. See Sample.

Additionally, if there exists a sufficient comfort level with installing and running .NET Dlls this thread may be of interest.

http://www.cadtutor.net/forum/showthread.php?t=34370

Farid · 8th Nov 2009, 01:52 am

the parabolas that I am working with are symmetric. what is see in the animation will fit my work, thanks. But is it in AutoCAD? because i could read in the command line "para" and when I tried it in AutoCAD, it does recognize this command. and what is NET Dlls?

SEANT · 8th Nov 2009, 02:32 am

The animation demonstrates a custom routine (written in C#.NET) located in this post of that thread:

http://www.cadtutor.net/forum/showpo...1&postcount=34

To install - Download the attachment, unzip, and locate the file ParabolaByUCS\Release\CsParabola.dll.

In AutoCAD:

Command: Netload

Then find CsParabola.dll

To run:

Command: pbb

The routine will produce a spline. If you prefer Splined 2dPolylines, or if your IT department frowns on third party customization, the process CarlB described, and I illustrated in the DWG above, should produce useful geometry.

Farid · 8th Nov 2009, 02:42 am

Thank you Seant! I'll play with it and if I had a question, I'll again ask.

7th Nov 2009, 09:15 pm	#1
Farid Forum Newbie Using: AutoCAD 2010 Join Date: Nov 2009 Location: Athens, Ohio, USA. Posts: 5	Draw a parabola I am working on vertical alignment of highways and need to draw draw a vertical, which is a parabola, in AutoCAD 2010. Anyone can help me.

7th Nov 2009, 10:35 pm	#2
ReMark Quantum Mechanic Using: AutoCAD 2009 Computer Details Join Date: Nov 2005 Location: Norwalk, CT USofA Posts: 10,833	What information do you have to work with? Can you share it with us?
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7th Nov 2009, 11:15 pm	#3
CarlB Super Member Version: not specified Join Date: Jul 2004 Location: Anchorage, Alaska Posts: 1,909	Discussed in this thread, with link to an earlier thread. http://www.cadtutor.net/forum/showthread.php?t=28775 "Vertical curves are parabolas, you can draw them by drawing a polyline from endpoint to VPI to endpoint, then PEDIT>>Spline. For it to be a proper parabola, set SPLINETYPE to 5 before pediting, and to get a smooth curve set SPLINESEGS to 15 or higher. (Thanks to rc McSwain for the Spline/parabola info)."

7th Nov 2009, 11:35 pm	#4
Farid Forum Newbie Using: AutoCAD 2010 Join Date: Nov 2009 Location: Athens, Ohio, USA. Posts: 5	i have the equation of the parabola, and I know the begging point of the curve, the vertex, and the end point of the curve. It will be very helpful if I can plot the equation. I tried the polyline, and then changed it to spline. But changes it's positing and became smaller.

7th Nov 2009, 11:47 pm	#5
CarlB Super Member Version: not specified Join Date: Jul 2004 Location: Anchorage, Alaska Posts: 1,909	If by "vertex" you mean the high or low point of the curve, then yes the curve will be inaccurate after "pedit". it should be initially drawn as two straight segments, from start curve, VPI (intersection of tangents) (VPT) to end of curve. if you want to plot the curve, you can do the calculations in Excel, with x & y values in adjacent columns; start the pline command, copy & paste values from Excel

8th Nov 2009, 12:07 am	#6
Farid Forum Newbie Using: AutoCAD 2010 Join Date: Nov 2009 Location: Athens, Ohio, USA. Posts: 5	yes, exactly. I mean VPI by vertex. If plot that in excel, then I think I won't be able export to AutoCAD so that I continue the further on based on what I exported. It will be only a raster image.

8th Nov 2009, 01:52 am	#8
Farid Forum Newbie Using: AutoCAD 2010 Join Date: Nov 2009 Location: Athens, Ohio, USA. Posts: 5	the parabolas that I am working with are symmetric. what is see in the animation will fit my work, thanks. But is it in AutoCAD? because i could read in the command line "para" and when I tried it in AutoCAD, it does recognize this command. and what is NET Dlls?

8th Nov 2009, 02:32 am	#9
SEANT Super Member Using: Mechanical 2009 Join Date: Aug 2005 Location: Rhode Island Posts: 1,182	The animation demonstrates a custom routine (written in C#.NET) located in this post of that thread: http://www.cadtutor.net/forum/showpo...1&postcount=34 To install - Download the attachment, unzip, and locate the file ParabolaByUCS\Release\CsParabola.dll. In AutoCAD: Command: Netload Then find CsParabola.dll To run: Command: pbb The routine will produce a spline. If you prefer Splined 2dPolylines, or if your IT department frowns on third party customization, the process CarlB described, and I illustrated in the DWG above, should produce useful geometry.

8th Nov 2009, 02:42 am	#10
Farid Forum Newbie Using: AutoCAD 2010 Join Date: Nov 2009 Location: Athens, Ohio, USA. Posts: 5	Thank you Seant! I'll play with it and if I had a question, I'll again ask.