Topic Title

Can I draw a parabola with DataCAD12?

If so How?

I know that in the Curves menu, you can use either B-Spline or Bezier to make a parabola. I just haven't figured out how the point definitions work. Through trial and error I've used to approximate a circular dormer coming into an inclined roof plane in a roof plan.
If you can figure out the rationality behind those point definitions, let me know.

Hi Kelly,

I'm afraid you will have not a ready tool for creating a parabola, but you can use a trick for getting your target closer: an Ellipse.

In the image below you can see that when using the double length (height) of your parabola you'll get it, starting by an ellipse.
At follow just use Erase/Partial for removing the exceeding half. Use an auxiliary layer for adjusting the guide lines.



Any chance to help ?

Thanks,
Miguel

I know that in the Curves menu, you can use either B-Spline or Bezier to make a parabola. I just haven't figured out how the point definitions work.

Our Bezier approximation method uses a standard mathematical definition for the curve. As I recall, B-Spline uses a 2nd Order algorithm to fit the curve to the control points. As for creating a hyperbolic, conic section, we do not currently have any built-in tools for it.

Dave

I can't say that I have had to draw a parabola since algebra class, but you could draw a cone, explode it to polygons and use the 3dknife function to cut it to create an approximation of a parabola and then trace it. Or draw a cone and a slab intersecting it and use the Boolean 3d function to subtract the slab from the cone to get an approximation to trace.

[Mark F. Madura]

If you're having trouble sleeping, read this.

Bézier
http://en.wikipedia.org/wiki/Bezier_curves

Parabola
http://en.wikipedia.org/wiki/Parabola

A three-point Bézier curve should produce a parabolic segment.



FWIW,

MFM

[Mark F. Madura]

If you explode a three-point Bézier curve into points, then rotate the points 'up', then rotate and copy the points about their center, then use the points to create a TIN surface, you end up with a Paraboloid.



FWIW,

MFM

Cool! I actually understand beziers now. I knew they had sumtin doin with parabolas. Thanks, Mark.

[Mark F. Madura]

You can approximate a quarter circle using a cubic (four-point) Bézier. In the illustration above, the distance from the first control point to the second point is 0.55228475 times the radius of the circle.

FWIW,

MFM

[Mark F. Madura]

Since the control points for the curve of a mesh surface are based on a cubic Bézier, you could use your new-found knowledge to create the following surface.



FWIW,

MFM