To Create a Curve on Surface (COS) by Points
Use the 
Curve tool to create a curve on surface (COS) by defining points on a surface.
Curve tool to create a curve on surface (COS) by defining points on a surface.1. Click 
Style > Curve. The Curve tab opens.
Style > Curve. The Curve tab opens.2. To create a curve on surface, click 
Curve on Surface.
Curve on Surface.3. To select the surface on which to place the curve, click the References tab, click the Surface collector, and select a surface.
4. Define points for the curve on the selected surface. A COS that goes through the definition points is created.
 | When you define COS points, you can hold down SHIFT to snap to other vertices or datum points as long as they all lie on the same surface. You can use control points and interpolation points. |
5. To define the curve using control points, click 
Control Points.
Control Points.6. To set the curve degree, type or select a value in the Degree box.
7. Closed curves are created as periodic. To change the closed curve to nonperiodic, click 
Periodic Curve. Click Periodic Curve again to change the curve back to periodic.
Periodic Curve. Click Periodic Curve again to change the curve back to periodic.| | For periodic curves, the value for the curve degree must be an odd number. When a curve of an even-numbered degree is changed to periodic, the degree increases by one. |
8. To maintain the curve shape during edits by moving the free points in proportion to the soft points, click the Options tab, and select the Proportional Update check box.
| | A curve without proportional update only changes shape at the soft point during edits. |
9. Click 
OK.
OK.