How to find tangent point at 30 degrees?


(Menno Deij - van Rijswijk) #1

Let’s say I have a curvy curve on the XY plane and I want to find the point where the tangent line is 30 degrees with the X-axis? How would you do this using just Rhino commands?


(Pascal Golay) #2

Hi Menno - a clunky way would be to make a 30 degree line nearby and use ClosestPoint> Object to find the tangent point on the curve.

Or, rotate the CPlane 30 degrees and use the Quad OSnap to locate the point.
! CPlane Rotate Z 30 Point Quad Pause CPlane Previous

-Pascal


#3

another–

make a line at 30º then use _Move with Tangent oSnap.

select an endpoint of the 30º line then move it along the curvy curve… it will snap into place when tangent.

(i personally also use the Near osnap… that way, your moving curve is tracking along the curvy curve then clicks into place when tangent… not necessary but just behaves better (to me) )


(David Cockey) #4

@pascal methods have a difference which may make one preferable.

[quote=“pascal, post:2, topic:45152”]
a clunky way would be to make a 30 degree line nearby and use ClosestPoint> Object to find the tangent point on the curve.
[/quote]This locates the single closest point on the curve to the line segment, which may be a tangent point or may be a kink, or depending on the length and position of the line segment the closest point to one end of the line segment which may not be a tangent point.[quote=“pascal, post:2, topic:45152”]
rotate the CPlane 30 degrees and use the Quad OSnap to locate the point.
! CPlane Rotate Z 30 Point Quad Pause CPlane Previous
[/quote]Only tangent points will be located with the Quad OSnap, and it will also locate all tangent points.


(David Cockey) #5

This method also will only find tangent points, and can locate all tangent points.