Ellipse tangent three lines how and best fit points?

[Steve1]

Hi,
V5

I hope the attached file save texture provides the jpg.

I am trying to best draw this S.
I need best fit elipse through these points. I have had such need before and never solved it.
No doubt V8 has such a basic tool by now. Look fwd to shrink wrap but basic tools are so important.
I thought V5 would have such.

I also need elipse tan to three lines, A B C and another at D E F for as you see it would do the job.
I also dont see that in V5.

Is that a plugin I can get ? ElipseTan3curve ???

One or the other would help, I do need tan to A B C to get the curves all ok.

Ideas ?

your approach ?
Fit elipses S.3dm (129.2 KB)

attaching jpg incase its necessary,
please advise.

(when I get this project done I can install V8)

With the discussion on use circle then scale1D it, I cant see how to scale it if two lines are 90deg and the third angled.

Ellipse tan to three curves is there a command else how?

The suggestion by @phcreates to use Scale1D is brilliant. The direction of the 1D scaling determines the orientation of the ellipse, and the amount of scaling determines the eccentricity. Draw a line parallel to the desired orientation of the ellipse. Place three points on the line with the ratio the distance between point 1 and point 2 to the distance between point 1 and point 3 equal to the desired eccentricity. Scale1D the lines with Copy=Yes. 1 is base, 3 is first reference point, 2 is s…

got as far as this but how does one scale 1D and get the circle to snap at the tan moment ?

Cheers

Steve

[pascal (Pascal Golay)]

Hello- what makes you think ellipses are what these images describe?

-Pascal

[Steve1]

Hi,
having spent 2 weeks creating a stencil alphabet tracing over such images for another style, the constant stroke width type, the S and 8 and 3 and such like ended up needing elipses. I started with circles and soon saw they didnt work, elipses fitted really nice.

I am following that design that 80 yrs ago seemed to be in the head of the creators.

However there is always that exception !

and if I find an elipse this time doesnt fit, then I would go off piste.

Steve

[Niels]

This would be an example of a real use case for the canned constraint WIP.

Rhino WIP Feature: Constraints

Constraints aren’t completely canned. I plan on picking them up again. One of the reasons for pivoting to other work was use cases failing to materialize for this project. It felt a little like a solution hunting for a problem. What would be helpful for kickstarting this when work resumes is real use cases and problem examples that would benefit from constraints.

When I need contraints Fusion is my go to, but there are other free CAD programs out there that have contraints.

Maybe it can be done in Grasshopper?

I hope the contraints feature is going to have a come back in Rhino 9.

[phcreates (peter harris)]

I guess you didn’t understand the solution in the other thread that you linked. It’s not difficult to create ellipse options that fit those three curves, if you also know the direction of the axes. It seems like you want the axes to be horizontal & vertical, so the attached is a simple example. Maybe I need to create a video to explain it better? I just copied your three curves multiple times. Then I scaled each set in Y, then drew a circle tangent to all three curves (I’m sure that tool has been around since v5, right?) Then use the Orient command with Scale=1D option to copy each circle back to your original curves. The scaling factor to complete the Orient command is just the length of B.

ellipse options.3dm (50.7 KB)