Distortable Circle

Is there a way to draw a 'circle' using Autocad (or any other drafting/
graphics software) that allows one to 'drag' the corner and side
handles (one at a time) and distort the circle, so that a continuous
curve is maintained, but the starting circle is now a free-form shape?

In my experience, the side handles give a 'transient' ellipse which
collapses to a smaller or larger circle with a new center.

Thanks,

baumgrenze

 

Not in Acad. A circle has a standard relationship between the center and the
perimeter.

 

In a previous post baumgrenze wrote...

A circle or ellipse has 5 handle points counting the center. To be able to
distort the shape as you describe would require more than 5 points. It may
be possible to trace over a circle or ellipse with a multi-point polyline
and then you can stretch it in any direct you wish, but it will still be a
series of line segments not a continuous curve.

There is a type of curve that may be what you are after. It's called a
bezier and can be pulled and stretched in many directions depending on the
number of points in the curve. I don't think ACad can draw that type of
curve, but other some other cad softwares can, Visualcadd for one.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

 

What about offsetting an "ellipse" and then the grips are independently
adjustable?

Maybe I'm not fully understanding what the person is trying to do?

 

Works for me. Create a symmetric ellipse then offset it.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

 

In a previous post roy wrote...

The original question was:

Is there a way to draw a 'circle' using Autocad (or any other drafting/
graphics software) that allows one to 'drag' the corner and side
handles (one at a time) and distort the circle, so that a continuous
curve is maintained, but the starting circle is now a free-form shape?

The above is possible if the "circle" is a symmetric ellipse that has been
offset some distance.

1. Create an ellipse with x and y axes symmetrical. This will look look a
circle.

2. Offset (or parallel) the ellipse. It will now have multiple grips, but
still look like a circle.

3. Grab any one of the grips and drag in any direction. Free-form shape!

4. It seems to me that you have done what the OP was asking for.


--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

 

Thank you all for your contributions.

It is clear that my goal is a far more complex one than can be
realized by an occasional user of Autosketch.

Here is the underlying problem I thought might be approachable using a
drafting program.

We wish to evaluate an individual's field of vision. From my limited
experience (I'm a retired chemist who has had his eyes checked many
times.) a 'normal' field of vision is approximately a circle. I
envisioned a test in which a technician could project a circle, and a
central focus-of-attention point, and then adjust 1/8th segments of
the circle inwards from 'eight points of the compass,' leaving the
ends connected, until the individual could just see the projected
curve. Small adjustments in and out would be easy to accommodate. The
resulting closed curve should be a pretty good map of the individual's
field of vision.

Here's another description of the task. Consider a circle to be a
cross section of a distortable spherical balloon. Allow the user to
'push' on eight (or perhaps more) uniformly placed points on the
circle and to displace them towards an apparent fixed center. Distort
the adjacent line segments so that the two next neighboring remain
fixed in place and a new continuous curve is maintained between
between them.

Perhaps the concept is 'simple' but its execution is non-trivial, at
least using drafting software. Perhaps it is more a problem
approachable using graphing software.

If this stimulates any alternatives, let's continue the discussion.

Thanks,

baumgrenze

 

Try pasting this into the command line:

rec 0,0 100,100 pe l s x ro l 50,50 45

 

In a previous post baumgrenze wrote...

They already have equipment that will do this. It projects dots of light
on a spherical field. You indicate which ones you can see by pressing a
button. The equipment then plots the resulting dots on a paper disk,
which in turn gives your field of vision.

I have this test done every year by my optometrist.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

 

and if you want the control points on the curve itself then use this:

spline -100,0 0,100 100,0 0,-100 c -100,-100