Hi Anis, MoI does an automatic refitting process for control point editing of arcs and circles. There isn't currently any way to turn it off.

This is to avoid a problem which is a frequent area of confusion in Rhino. In Rhino after you draw a circle and turn on control points, you will see control points like this:



Then if you edit those points, you will see this kind of result:



Most people are very surprised by getting this result with those sharp points at the quadrant areas. Since a circle starts out smooth, most people expect getting a smooth result when you edit it. In Rhino to get a smooth result you have to do some extra steps, either use the "Deformable" when you create the circle or use the Rebuild command on it. It's something extra that you have to learn and that's exactly the kind of thing that I have tried to reduce in MoI.

MoI applies a kind of automatic "deformable" option when you turn on control points for an arc or circle curve like this, so you don't have to do any extra steps to get the expected result when editing a circle. This is also applied to arc curves, and it involves replacing the degree 2 arc segment (with 3 points in it), with a degree 3 general curve segment. A degree 3 curve will have a minimum of 4 points in it.


I suppose it should be possible for me not to do this refitting when the arc has only 3 points in it, which is usually the case for an arc of 90 degrees or less. I'll take a look at that.

In the meantime if you really want a 3 point curve in those corners, you will have to use Edit/Separate to break the curve into segments, delete the existing arcs and draw in a new curve segment there using Draw curve / Freeform / Control points and use only 3 points for that new drawn curve, that should create the kind of point structure that you want there.

- Michael