# Locate a point on "Ellipse arc" to get chord of desired length

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Hi everyone,

is it possible to get a point on an "ellipse arc", in an specified distance to the start point of "ellipse arc"?

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Hi everyone,

is it possible to get a point on an "ellipse arc", in an specified distance to the start point of "ellipse arc"?

```
(setq sel (entsel))
(setq ent (car sel))
(setq obj (vlax-ename->vla-object ent))
(setq res (vlax-curve-getPointAtDist obj 2.0)) ;; where 2.0 is the desired distance

```

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```
(setq sel (entsel))
(setq ent (car sel))
(setq obj (vlax-ename->vla-object ent))
(setq res (vlax-curve-getPointAtDist obj 2.0)) ;; where 2.0 is the desired distance

```

But unfortunately vlax-curve-getPointAtDist behaves like MEASURE command. It doesn't return the desired point. I want to find point on the curve with straight certain distance from its start point.

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Hi everyone,

is it possible to get a point on an "ellipse arc", in an specified distance to the start point of "ellipse arc"?

But unfortunately vlax-curve-getPointAtDist ...... doesn't return the desired point. I want to find point on the curve with straight certain distance from its start point.

OK, you did not say that you wanted the straight linear distance in your original request.

Do you mean like in the image below?

Then draw a circle from the startpoint with a radius = the desired distance, and then find the intersection of the elliptical arc and the circle.

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Then draw a circle from the startpoint with a radius = the desired distance, and then find the intersection of the elliptical arc and the circle.

Thank you R.K.McSwain for the good offer, but...

Finding the intersection of two curves, this is the problem!

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Finding the intersection of two curves, this is the problem!

Here is an example:

```
(setq a (car (entsel)))
(setq b (car (entsel)))
(foreach item (ACET-GEOM-INTERSECTWITH a b 3)
(vl-cmdf "._circle" item (* 0.02 (getvar "viewsize")))
)

```

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Thank you R.K.McSwain for the good offer, but...

Finding the intersection of two curves, this is the problem!

if you cannot find the INT of two curves, you should certainly be able to trim one to the other. then used the end point.

good luck.

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Here is an example:

```
(setq a (car (entsel)))
(setq b (car (entsel)))
(foreach item (ACET-GEOM-INTERSECTWITH a b 3)
(vl-cmdf "._circle" item (* 0.02 (getvar "viewsize")))
)

```

Nice and very good function: ACET-GEOM-INTERSECTWITH

R.K.McSwain, I appreciate your great help:D.

Edited by Ahankhah
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if you cannot find the INT of two curves, you should certainly be able to trim one to the other. then used the end point.

good luck.

lamensterms, your method works very good in lack of express tools. Thank you very much.

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Finding the intersection of two curves, this is the problem!

Perhaps these will help, I try to avoid dependence on Express Tools functions as much as possible.

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Perhaps these will help, I try to avoid dependence on Express Tools functions as much as possible.

It's about time... I knew you would be along with something....

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It's about time... I knew you would be along with something....

........

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........

Yea, I don't like using code that you don't have the source to either.... but in this case, it was more of a "yes, it can be done" type of reference....

Glad to know you got that intersection stuff covered also...

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Perhaps these will help, I try to avoid dependence on Express Tools functions as much as possible.

Lee,

as always you have the best answer to everything. :lol:

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no worries mate. glad i could help.

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Lee,

as always you have the best answer to everything. :lol:

Thanks Mehrdad, I try my best

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