Bug: Unwanted snapping with Line tangent

Sometimes there is an unwanted snapping with the ! _Line _Tangent _Pause command while reaching the end of an arc with the mouse pointer. You can clearly see this bug in the video below. I also attach the same curves to try the bug by yourself. It has happened multiple times to me over the past years.
The funny thing is that once I make it work properly, every next time it works as expected. However, when I undo the action and try the command again, the bug happens is also present. I tried this several times after I recorded the video.

However, the following macro…
! _CPlane _Object _Pause _ProjectOsnap _Toggle Enter _Pause _Line _Tangent _Pause _Pause _Cplane _Undo _ProjectOsnap _Toggle Enter
… works perfectly fine every time, whereas the default command ! _Line _Tangent _Pause fails. :slight_smile:

Bug - Unwanted snapping with Line tangent.3dm (103.2 KB)

Hi Bobi - I think you’ll find that the ‘snap’ occurs when the start points hits the end of the arc.


@pascal , if you take a closer look the beginning of the video, you will notice that Rhino literally makes it impossible to build the tangent line in a location just before its starting point reaches the left end of the arc. This is a few degrees of “prohibited zone” where the problem occurs. This particular behaviour has happened to me hundreds of times during the years and it’s clearly some stubborn bug related to arcs that are the result of split circles. :slight_smile: