# Wish: edit edge tangency angle

Currently the only option I have is rotate an edge which rotates it about it’s CoG and that’s not really good because it requires adding another face, or more.

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You can relocate the Gumball using Ctrl or use the Rotate command on a sub-object. Does that help?

Not unless control-point-rotation is allowed in Rhino.

A single point has no size to rotate so I think I’m misunderstanding what you need. Can you explain more? My guess was that you wanted to rotate an edge from a spot other than it’s bounding box center.

Yes, but the tangent vector at this point of the edge can be.

(again I do not know the math behind subd) but it looks a lot like b-splines that maintain g3 continuity.

Imagine if a 3d rotation of the vertex in fact rotates the first immediately connected control point to it about that vertex that’s selected. This will change the tangent direction of the subd. This will allow to create a trumpet-ish edge out of a cone primitive subd without having to add one or more additional subd faces.

PS: Btw that same behavior when rotating control points of nurbs surfaces will bring quite a lot of value IMO.

I think this is possible now by rotating an edge about a vertex. You can use the Align to Object setting in the Gumball when sub selecting an edge as well to align one axis to that edge. My understanding is that you’d have to rotate the entire edge rather than a single point. I think I know what you mean though when editing bezier splines in say Illustrator where you can introduce kinks along a curve by breaking tangency. To my knowledge this is not how NURBS or SubD surfaces work and if you want to create a sudden change in direction you’ll need to add more edge loops. On a NURBS surface you’d add more control point rows or trim the surface and work from that edge.

I’d be happy to file a feature request though for the math geniuses to investigate if you can show me an example of what you need to model

not to rotate the edge, to bend it. Currently whatever the form of the edge is you’ve no option to change it. You can’t straighten a curved edge or bend a straight one. You can only rotate, offset and move it.

I’ll think of an example and I’ll post it here.