To Create a New Curve
1. Click 
Style > 
Curve. The Curve tab opens.
Style > Curve. The Curve tab opens.2. To specify the curve type, click an option:
◦ Free Curve—Creates a free curve that lies in three-dimensional space and is not constrained by any geometric entity.
Free Curve—Creates a free curve that lies in three-dimensional space and is not constrained by any geometric entity.◦ 
Planar Curve—Creates a planar curve that lies on a specified plane.
Planar Curve—Creates a planar curve that lies on a specified plane.◦ 
Curve on Surface—Creates a curve on surface that is constrained to lie on a specified single surface.
Curve on Surface—Creates a curve on surface that is constrained to lie on a specified single surface.3. Define points for the curve. You can create Style curves using control points or interpolation points.
4. To define the curve using control points, click 
Control Points.
Control Points.5. To set the curve degree, type or select a value in the Degree box.
6. 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. |
7. To create a curve that is symmetric, for a free or planar curve, on the References tab:
a. Select the Symmetrical Curve check box.
b. Click the Plane collector, and then select a datum plane to define the symmetry plane for the curve.
c. If required, to reverse the curve direction, right-click the curve and choose Flip Curve Direction.
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.