How to build a oval?

Replies to This Discussion

Permalink Reply by Taylor on March 6, 2012 at 5:03am

I mean the 3d oval. not 2d..

Permalink Reply by Danny Boyes on March 6, 2012 at 5:07am

use a Sphere and the Scale NU component

Permalink Reply by Taylor on March 6, 2012 at 6:02am

thanks, seems like this is the only way I can do it...

Permalink Reply by Taylor on March 6, 2012 at 6:48am

Aha, sorry, Im stupid, once we set up the sphere Dimention to 1 the scale is precise, thanks!!  

Permalink Reply by Robert Narracci on April 24, 2014 at 1:09pm

Just came across this searching with the same question. I'm pretty sure scaling a sphere yields an ellipsoid and not an ovoid.

Permalink Reply by Michael Makris on April 24, 2014 at 6:09pm

What is  your definition of an Ovoid? I am not familiar with (nor can I find) any mathematical definition of an oval.

Assuming you just want an ellipsoid, the other answers work great.

Permalink Reply by Robert Narracci on April 24, 2014 at 8:17pm

Ovals and ellipses are superficially the same but different mathematically and in projection. An ellipse can be drawn with a pencil and two pin points connected by a string longer than their distance, whereas an oval is two pairs of circles trimmed tangent to one another. I was literally looking to reproduce an egg (oval comes from the Latin ovum) which is has only one axis of symmetry. Scaling a sphere won't produce an egg shape. I've been wrestling with ways to create a tangent arc between two circles (of different radii) but unfortunately the GH component only seems to yield concave tangent arcs. I'm not trying to be a wise-acre...just trying to draw an egg.

Permalink Reply by Robert Narracci on April 25, 2014 at 5:13am

MKT,

Looks like what I was trying to do but the fairing btwn the spheres was inverted (concave). I was using the Tangent Arc Between Circles. Did you find a way of making that component do a convex arc or did you use some other way?

Permalink Reply by Sridevi Koonath on April 25, 2014 at 7:14am

Hello Robert,

I had made this little script for a friend last year, using one of the equations off the internet, for egg-shape. It's not perfect since the base of the "egg" is flat (it was supposed to be an egg-shaped building), but maybe it is of some use to you?

Permalink Reply by Robert Narracci on April 25, 2014 at 7:42am

Very elegant. Thank you Sridevi!

Its interesting that along with the egg formula (I didn't know there was one), there's also a drawing method similar to the classical ellipse method with a string, only with three pins instead of two. I found it here...

http://www.mathematische-basteleien.de/eggcurves.htm

Permalink Reply by Sridevi Koonath on April 25, 2014 at 10:03am

Ah neat, then you can apply the method in Grasshopper to get the perfect curve and the perfect egg!

I vaguely recall seeing this webpage myself, though I didn't think to get the curve in this manner :-|