The farthest X point and Y point

[cadking2k5]

here is a Ellipse drawn from Spline command Tangent doesn't work right on this is there a way to find the point that is the farthest X east and the farthest west X point and same North and South with Y

[Kent1Cooper]

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@cadking2k5 wrote:

here is a Ellipse drawn from Spline command Tangent doesn't work right on this is there a way to find the point that is the farthest X east and the farthest west X point and same North and South with Y

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@cadking2k5, we need some clarification.  Obviously people are interpreting what you want in different ways.  Could you re-post the images from Posts 1 and 14, with dots or something showing the locations you are trying to find?

[cadking2k5]

@marko_ribar find the farthest East X Point and West X point on this SPINE Ellipse

[cadking2k5]

@marko_ribar your ellipse is not touching the line

[marko_ribar]

This must be a joke... I have better things to do than finding your points in messy drawing...

And my ellipse is touching line, just computation and drawing based on segmentation is not 100% accurate... This bounding box is only based on principal directions which are calculated somewhat inaccurate because of segmented region, so the whole thing is little problematic, but process is correct in terms of studying what resulting outcome is - ellipse and not a spline...

[SEANT61]

Do any of these help?

[john.uhden]

That should be, "Does any of these help?"  Any is singular, as in any one.  "Of these" is is just an adjectival phrase.  It would be different if you had said, "Do these help?" 

[marko_ribar]

This by @SEANT61 reminds me on this :

http://www.lee-mac.com/5pointellipse.html

HTH., M.R.

[SEANT61]

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@john.uhden wrote:

That should be, "Does any of these help?"  Any is singular, as in any one.  "Of these" is is just an adjectival phrase.  It would be different if you had said, "Do these help?" 

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Let me acknowledge up front that I’ve been honing my butchery of the English language for many years now.  I just never found grammar particularly interesting.

Your confidence to make such a comment leads me to believe that you know what you are talking about. 

Those statements notwithstanding, this case interests me.  My drawing includes three different examples of a procedure that may or may not be useful to the OP.  Does “Any” imply singular?  In that case I certainly did misspeak/type.   I tend to think that my posts/DWGs are so frikken helpful that readers find nuggets of usefulness in just about all the examples.  

[SEANT61]

Certainly a good choice, but not what I used to generate the ellipse. 

I used:

https://apps.autodesk.com/ACD/en/Detail/Index?id=7033830822584405086&appLang=en&os=Win32_64

which uses a different algorithm than the one used in Lee Mac's routine.

[marko_ribar]

@SEANT61

Is your e-mail the same?... I think my archive link changed (this happens when updating archive with some stuff and when packing - archive fails to do it correctly, so I then have to rename it to ZIP again)...

[SEANT61]

Reply made by private message.

[john.uhden]

Actually, your english don't make no difference.  It's the nuggets that count.

[cadking2k5]

@SEANT61 That is a really good job but I set the Arc and Circles Smoothness at 20000 and the Ellipse and the line don't touch they are of just a very little just like I draw an Ellipse and use the Diameter as from the center to the upper right corner and rotate it at the angle it is at and how did you get the center point and those points for the axis on these ellipse.

[SEANT61]

Sometimes the graphical display of AutoCAD entities can be misaligned.  I haven't done it myself but try to trim the ellipse with the tangent line and see what happens.

With regard to creating the ellipse - I, too, used a spline as an intermediate entity.  See the general procedure in the screencast I included in this thread:

https://forums.autodesk.com/t5/autocad-forum/ellipse-inscribed-within-a-parallelogram/m-p/5908700#M8...  

The properties of that spline were used to recreate the ellipse.

[SEANT61]

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@john.uhden wrote:

Actually, your english don't make no difference.  It's the nuggets that count.

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Hah, now I see it.  I didn't actually pick up on it first time around.

Interestingly enough, cohorts in my industry will often remark "that ain't never gonna go nowhere!" regarding items that have been securely fastened into place.  Though computationally expensive, at least the triple negative has the intent pointing in the proper direction.

[stevor]

In the same plane, make a circle about the point,

that encloses the ellipse/any-curve;

and walk the distance between the curves to a minimum,

with vlax-curve-getClosestPointTo.

[cadking2k5]

@marko_ribar that is good but what is that 45° for and how did you get that angle 46.83524825° for the axis of the the ellipse and some parts of it is off by 0.00047750

[marko_ribar]

AFAIK, you can get correct ellipse in parallel projection in 2 different ways...

1. look into screen cast posted in link by @SEANT61... You'll notice that he constructed 4 helper 2nd degree splines with weights of control points 1, (sqrt 0.5), 1 and then he connected them with JOIN command... After that you can use region command to get adequate region entity from which you can get correct main principal directions with (vla-get-principaldirections (vlax-ename->vla-object regionentity))... When you get correct directions you can reconstruct correct bounding rectangle and then inscribe correct ellipse after which you can remove helper region...

2. you can project 5 points from main orthogonal projection of circle/ellipse on your parallel projection... Then you simply apply Lee Mac's 5 point ellipse on those transformed points and you'll get correct ellipse...

M.R.

[Kent1Cooper]

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@Kent1Cooper wrote:

@cadking2k5, we need some clarification.  Obviously people are interpreting what you want in different ways.  Could you re-post the images from Posts 1 and 14, with dots or something showing the locations you are trying to find?

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I repeat the question, and add another:

It seems a lot of recent Posts here are about finding the Ellipse that represents a Circle [or another Ellipse] fitting an existing parallelogram  that respresents a square or rectangle in some kind of oblique/projected view.  But the original Post 1 is starting from an already-existing elliptical (+/-) Spline, which must have come from somewhere -- perhaps based on something like a similar parallelogram, but I can't tell.

SO:  Is a way of making a true Ellipse relative to existing geometry, instead of  a Spline approximation, going to serve your purpose, or are you looking for a way to find points  [whatever points they are supposed to be -- see question above] on an already-drawn  Spline-form ellipse approximation?  The original question suggests the latter, because if you already have the parallelogram [or whatever geometry the Spline was generated from], presumably you can get the points you want from that [likely midpoints of edges, but it's still not clear to me].  But if  it's the latter, all the offerings about generating the true Ellipse, however interesting, seem irrelevant.

[john.uhden]

@Kent1Cooper wrote, "... all the offerings about generating the true Ellipse, however interesting, seem irrelevant."

Agreed, except for the interesting part.

The Horizontal Elliptical Reinforced Concrete Pipe (HERCP) that we design is not an ellipse at all.  It has two larger radii and two smaller radii that sort of look like an ellipse.  All that matters is the area and wetted perimiter as a function of depth of flow within the pipe.