Sphere

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->Sphere command allows you to define a sphere, a 3D object that may be a polygon mesh, a patch, or a NURBS surface.

For patch spheres, you can specify the type of curve used in the u and v directions; for NURBS, you can specify the degree of curve in each direction.

Polygon mesh spheres are closed. By default, patch and NURBS spheres are closed in u and open in v.

1. Choose the Get->Sphere command.
   
   The Create Sphere dialogue box is displayed.
   
2. Select Polygon, Patch, or NURBS for the object type.
3. For all sphere types, set the radius and the number of Steps in Longitude and Latitude.
4. For Patch surfaces, select the type of curve (Linear, Cardinal, or B-Spline) for longitude and latitude (U and V directions).
5. For NURBS surfaces, select the degree of the curve (Linear, Quadratic, or Cubic) for longitude and latitude (U and V).
6. Click Ok or Cancel.

Parameters

Object Type

• Polygon creates a polygon mesh sphere.
• Patch creates a patch sphere using Linear, Cardinal, or B-Spline curve types for longitude/latitude (U and V).
• NURBS creates a NURBS sphere of the first degree (linear), second degree (quadratic) or third degree (cubic), in either the U or V direction, or both.
  • Linear creates a NURBS surface of the first degree in the chosen direction. The resulting direction is of continuity zero (positional continuity). This is the default value.
  • Quadratic creates a NURBS surface of the second degree. The resulting direction is of continuity 1 (positional and tangential continuity).
  • Cubic creates a NURBS surface of the third degree in the chosen direction. The resulting direction is of continuity 2 (positional, tangential, and curvature continuity).

Radius

Size of sphere in SOFTIMAGE units.

Longitude (U) Step

Number of equidistant subdivisions on the vertical axis.

Latitude (V) Step

Number of subdivisions on the horizontal axis.

Tip:

It is often useful to cap a patch or NURBS surface in V. To do this, select the sphere and choose Info->Selection. In the dialogue box that appears, select the Capping options for Bottom and Top in V. Bottom refers to the start of V direction and Top refers to the end of V direction. After capping, the top or bottom points of the sphere move as one. Compare the results with and without capping.

Last updated 02-apr-1998