Spiral

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->Spiral command creates a spiral, which is an open 2D curve.

1. Choose the Get->Spiral command.
   
   The Create Spiral 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: Starting and Ending Radii, Starting and Ending Angles, Depth, and Step.
5. Click Ok to accept, 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 two (positional, tangential, and curvature continuity).

Starting Radius

Size of the spiral in SOFTIMAGE units at the start.

Ending Radius

Size of the spiral in SOFTIMAGE units at the end. Together, the two radius parameters determine the shape of the spiral: conic or cylindrical.

Starting Angle

Angle of the first point.

Ending Angle

Angle of the last point.

Together, the two angle parameters determine the curvature of the spiral. Use the Front window centre as a reference point for these angles.

Depth

Size of the spiral in SOFTIMAGE units and starting from the origin the world. Use the Top or Right window for reference.

Step

Number of control points (definition).

Last updated 02-apr-1998