Geodesic line/curve tangent to a circle in V5

[fredtheblue]

I've been trying to do the following but after asking many people haven't got an answer:-

(This works perfectly with the Geodesic function on V4)

In GSD, how do I place a line/curve on a surface whose origin is a point anywhere on that surface, and which is tangential to a circle or curve that already lies on that surface?
I dont want this new entity to be parallel with an existing curve.
Seems simple but i cannot find a solution.

 

[solid7]

Sorry, Fred. The wonderful command called "Geodesic" is not to be found in V5. The workarounds are complex, and inelegant.

To make this answer short - you need to create supporting geometry. (surfaces, lines, etc - and intersect with the surface)

Wish I could be more positive, but I've been frustrated by this. Hopefully someone can chime in and suggest a better method, or at least give the lowdown on a workbench that maybe I don't have, to accomplish this.

---
CAD design engineering services - Catia V4, Catia V5, and CAD Translation. Catia V5 resources - CATBlog.

 

[JuhaEdag]

One method is to project the existing curves on the surface along a direction to a plane. Work on the plane creating your tangent geometry etc. either through work on support alternatively a sketch and then project them back to the surface along the same direction (or create an extrusion in the same direction and intersect the surface).

 

[jackk]

Fred,

Many of the V4 Geodesic constructions are available as the GEOMETRY ON SUPPORT option in the feature creation panel (such as circle and spline).

Another way to get Geodesic geometry is to use WORKING SUPPORT and select a surface.

However, I haven't been able to use either method to draw a tangent line (curve) between a point and a circle.

I've done what Juha suggested with good results.

If you have the license for Developed Surfaces and you're working with ruled surfaces, you can also use FOLD and UNFOLD to semi-automate Juha's method.

 

[catiajim]

GEOMETRY ON SUPPORT should work, but it doesn't seem to in R14 or R16. You should simply be able to create a Line, Tangent To Curve, select your curve, select your point, and select the surface as a support.

What I get, however, is WRONG. It is giving me a line parallel to a line that would be tangent to the curve thru the point AS PROJECTED ONTO THE CURVE. Dead Wrong! Sounds like PMR Time.

 

[jackk]

Jim...

I think TANGENT TO CURVE is working correctly, or at least it's doing what it always did. But it's not the line that Fred wants.

 

[jackk]

Make sure you use the BITANGENT option!

 

[catiajim]

You're right, jackk. Unfortunately, BiTangent requires a planar support.

A perfect example of "Works as Designed" but the design is @#$%^