topic Betreff: Line intersecting two curves at equal angles in AutoCAD Forum

Line intersecting two curves at equal angles

Anonymous — Thu, 13 Sep 2018 13:38:44 GMT

Hello,

I need to create an array of lines that intersect splines at equal angles. I've attached a dwg file and a jpeg file to illustrate what I need to achieve.

Each line in the array should intersect both spline curves at equal angles. However, the angle that the lines intersect the spline curves do not need to be equal from line to line. For example, if one intersecting line in the array intersects each of the two splines at 90 degrees, the next intersecting line in the array does not need to intersect the two spline curves at 90 degrees.

James

Re: Line intersecting two curves at equal angles

beyoungjr — Thu, 13 Sep 2018 15:58:17 GMT

Did you try Path Array?

1. Pre-select one of your existing lines.

2. Click the drop-down arrow beside the Array button (Modify Panel of Home Ribbon).

3. Choose Path Array on this menu.

4. The Array ribbon appears.

5. Change the distance between items to 10 or something(default setting is "1" on your dwg file).

The Array ribbon also offers you options such as "Align Items". Change options to see a preview of the result before clicking "Close Array".

One thing many users may miss is "Associative". This button groups all items in the Array if active. I typically avoid the Associative option but there are great examples where it may be useful.

Your post asked about intersecting at equal angles but distance between the intersecting items is probably the more appropriate descriptor. I an't really think of how to apply the concept of equal angles to the desired image because the resulting angles are dictated by the shape of your contour path/s.

Hope this helps,

Blaine

Betreff: Line intersecting two curves at equal angles

j.palmeL29YX — Thu, 13 Sep 2018 16:35:05 GMT

@Anonymous schrieb:

Each line in the array should intersect both spline curves at equal angles.

I'm afraid in AutoCAD you can't solve this problem.

In this screencast https://knowledge.autodesk.com/community/screencast/73841c69-7948-4b9f-bce8-59e4ddcd5ba7 I show the result how I would do it in another software (Autodesk Inventor).

- draw two construction lines which touch permanently the spline and are always tangential to the spline (using constraints)

- draw the whished line from Endpoint to endpoint

- add two angle dimension and restrict this dimensions to be equal

In the video you see: If I drag the result line along the splines, it touches the splines at both sides always with the same angle to the tangent line at this point.

So you can draw as many lines as you want.

Unfortunately this doesn't work in AutoCAD, because there is no possibility to draw (and restrict) a line tangential or perpendicular to a spline. And also no possibility to restrict two angle dimensions to get always the same value.

cadder

Betreff: Line intersecting two curves at equal angles

leeminardi — Thu, 13 Sep 2018 18:58:39 GMT

I think the method outlined by @Anonymous is the way to go. Very slick!

However, if you do not have access to Inventor and are willing to accept an approximate solution you could use the parametric features of AutoCAD.

First approximation would be to approximate the shape of the splines by a series of arcs. This can be easily done by creating a polyline using the A (arc) option along with object snap near.

The second approximation is the use of a very small circle to represent the tangent point of a line with an arc. The center of this circle is necessary as a reference point for drawing the line between the two "splines" (arcs).

The arcs are fixed in space with fixed and radial dimension constraints. The two small circles have tangent constraints with the adjacent arcs and lines. Coincident constraints are used at the ends of all touching lines.

Here you can see the small circle that acts as the tangent point. It can be made smaller.

You can obtain additional solutions by changing the angle value (the angle at the bottom references the top angle value).

Betreff: Line intersecting two curves at equal angles

j.palmeL29YX — Fri, 14 Sep 2018 04:58:59 GMT

A slight improvement of @leeminardi's suggestion.

We need only one approximation - replace the spline with arcs. But we don't need the circles. Draw (at each arc) a construction line with one endpoint coincident to the arc and perpendicular to a construction line which is restrictet to the centerpoint of the arc. (I have had a similar try, but tangent to the arc. This didn't work). Now you can choose one of the angles (in my attached example set Win2 to 95, 90, 85, ...), the other angle is restricted to be equal and we get correct results. But as told this only works with arcs, not with splines.

cadder