Plotting a Parabola

[jclough]

At the risk of sounding foolish....Is there an easy way to draw a parabola?

 

[IFRs]

Autocad does not have a built in parabola. I'd use a spreadsheet to calculate the X and Y and then use a script to draw a polyline from those points.

 

[lpseifert]

Maybe something here will be of use, you need to register but it's free

http://www.theswamp.org/index.php?topic=15144.0

____________________
Civil 3D 2008, Terramodel

 

[chicopee]

Yeah, use the UCS as the origin and then type the positions of X&Y values as points, then polyline between points or nodes. To remove the discrite shape invoke the FIT option under PEDIT to smooth out the curve.

 

[CarlB]

A quick, and I believe accurate way to draw a parabola is as follows. This method appies to a parabola as used for a balanced roadway vertical curve):

Draw 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/parobola info).

 

[chicopee]

Carl,you should not use a spline because it is a statistical; you are better off to use a polylineand use thefit option tosmooth out the curve.