Arc

The Get->Primitive commands are available in all modules except Tools. They let you define primitive objects which are basic objects with a fixed geometric structure.

For detailed descriptions of polygon mesh objects, curves, and surfaces, as well as the modelling tasks you can perform with them, see the Modelling User's Guide.

The Get->Arc command allows you to define an arc, which is an open 2D curve.

1. Choose the Get->Arc command.
   
   The Create Arc dialogue box is displayed.
   
2. Select the type of curve (Linear, Cardinal, B-Spline, or NURBS).
3. For NURBS curves, select the degree of curve: Linear (the default), Quadratic, or Cubic.
4. Set the parameters Radius, Begin, End, and Step.
5. Click Ok to accept the settings or Cancel to exit.

Parameters

Curve Type

• Linear: Straight line between control points.
• Cardinal: Curved line passing through control points.
• B-Spline: Curved line not necessarily passing through control points.
• NURBS: Curved line not necessarily passing through control points. Specify the degree, which affects the smoothness and continuity of the curve.
  • Linear creates a NURBS curve of the first degree. The resulting curve is of continuity zero (positional continuity). This is the default value.
  • Quadratic creates a NURBS curve of the second degree. The resulting curve is of continuity 1 (positional and tangential continuity).
  • Cubic creates a NURBS curve of the third degree. The resulting curve is of continuity 2 (positional, tangential, and curvature continuity).

Radius

Size of arc in SOFTIMAGE units.

Begin

Starting point degree reference (0 ° = 3 o'clock).

End

Ending point degree reference, up to a maximum of 360°. The default is 90° = 12 o'clock.

Step

Number of control points (definition).

Last updated 02-apr-1998