Control multi-knots and CV hardness

Multi-knots are multiple edit points at the same location that create a sharp bend or corner in a curve. For example, the Create > Text tool creates curves with multi-knots to represent letters with sharp corners.

Hardening a CV edge

“Hardening” a CV creates multiknots that make the curve take a sharp turn at the CV.

To set the hardness of a CV

Select the CVs.
You can only harden a CV if the previous and next CVs on the curve are not hardened.
Select Edit Curves > CV Hardness > .
Do one of the following:
- Click Full to make this a hard CV, resulting in a sharp bend in the curve.
- Click Off to make this a normal CV, resulting in a normal (softer) bend of the curve.
If you turn on Keep Original, Maya will create a new curve with the hardness applied to the CV. In the dependency graph, you can see a node that takes the original curve, hardens the CV, and outputs a new curve.

You can select this node and turn the hardness on or off using the Multiplicity slider in the attribute editor.

If you turn off Keep Original, the operation applies to the CV on the original curve and is not editable.
Click Harden.

Adding or removing a tangent break at an isoparm

A tangent break inserts multi-knots along an isoparm to break tangent continuity. This lets you make a sharp bend in the surface along the isoparm. The shape of the surface doesn’t immediately change.

To...	Do this
Break tangency along an isoparm.	Select the isoparm and choose Edit NURBS > Surface Editing > Break Tangent.
Break tangency along isoparms in both directions.	Select a surface point and choose Edit NURBS > Surface Editing > Break Tangent.
Break an arbitrary tangent.	Use the Surface Editing tool to select the tangent direction, then choose Edit NURBS > Surface Editing > Break Tangent. Reshape a curve or surface manually
Smooth a broken a tangent.	Select the isoparm and choose Edit NURBS > Surface Editing > Smooth Tangent.

Note Edit NURBS > Surface Editing > Break Tangent sometimes doesn't work for U direction isoparm of closed surface.

If this happens, use Edit NURBS > Move Seam first.

To remove multi-knots from a curve

Select the curve.
Choose Edit Curves > Rebuild Curve > .
Set Rebuild Type to No Multiple Knots.
Click Rebuild.

To remove multi-knots from a surface

Select the surface.
Choose Edit NURBS > Rebuild Surfaces > .
Set Rebuild Type to No Multiple Knots.
Click Rebuild.