Hi Pilou,

> Yes this gives the helper line on somewhere must be the center's circle inside the sphere
> but not the deepth... ;)

Well you could use it for example to help draw a cylinder that had a central axis perpendicular to the surface of the sphere but partially submerged inside of it rather than sitting exactly on the tangent plane. Then with the cylinder intersecting the sphere you can intersect them.


> Not yet found for example the use of the Orient only for place the circle on this line..

It will be difficult to find the exact location to position the circle doing it that way - I'd recommend instead using a projection method so that you don't need to worry about the positioning in a manual way like that.

- Michael