topic Re: how do you find the tangent of point to curve in autocad api in .NET Forum

how do you find the tangent of point to curve in autocad api

Dannyisrael — Sat, 12 Feb 2022 10:44:11 GMT

Re: how do you find the tangent of point to curve in autocad api

Jeff_M — Sun, 13 Feb 2022 04:44:55 GMT

Option 1: Calculate the angle with a little Trig. You know that you have a triangle formed by the radius (R), the tangent line (T) and the line from point to radius point (H), You know (or can easily get) the lengths of the last 2 so the angle from the H to T would be arcsine (r/h). Now add or subtract the found angle to/from the angle of H.

Option 2: Similarly, you can calculate the length of the Tangent line since it a basic right triangle. Construct a temporary circle from the known point having that radius and use IntersectWith between the circle and arc to find the point of tangency.

Re: how do you find the tangent of point to curve in autocad api

R.Gerritsen4967 — Wed, 16 Feb 2022 08:23:54 GMT

I use this piece of code from @_gile :

Public Function GetTangentsTo(ByVal arc As CircularArc2d, ByVal pt As Point2d) As Point2d Dim center As Point2d = arc.Center If pt.GetDistanceTo(center) <= arc.Radius Then Return Nothing Dim vec As Vector2d = center.GetVectorTo(pt) / 2.0 Dim tmp As CircularArc2d = New CircularArc2d(center + vec, vec.Length) Dim inters As Point2d() = arc.IntersectWith(tmp) If inters Is Nothing Then Return Nothing Dim tanPt As Point2d If inters(0).X > inters(1).X Then tanPt = inters(0) Else tanPt = inters(1) End If Return New Point3d(tanPt.X, tanPt.Y) End Function

Re: how do you find the tangent of point to curve in autocad api

norman.yuan — Fri, 25 Feb 2022 04:07:32 GMT

You might want to read this:

https://drive-cad-with-code.blogspot.com/2022/02/where-tangent-point-is-show-it-when.html

Re: how do you find the tangent of point to curve in autocad api

Dannyisrael — Tue, 01 Mar 2022 14:39:33 GMT

Thank

Re: how do you find the tangent of point to curve in autocad api

Dannyisrael — Tue, 01 Mar 2022 14:40:17 GMT

Thank you