Creating Spherical Surfaces

	This task shows how to create surfaces in the shape of a sphere. The spherical surface is based on a center point, an axis-system defining the meridian & parallel curves orientation, and angular limits.
	Open the Sphere1.CATPart document.
	Click the `Sphere` icon from the Extrude-Revolution toolbar. The Sphere Surface Definition dialog box is displayed.
	Select the center point of the sphere. Select an axis-system. This axis-system determines the orientation of the meridian and parallel curves, and therefore of the sphere.
	By default, if no axis-system has been previously created in the document, the axis-system is the document xyz axis-system. Otherwise the default axis-system is the current one.
	Click Apply to preview the surface.
	Modify the `Sphere radius` and the `Angular Limits` as required. Here we choose -90° and 90° for the parallel curves, and 240° and 0° for the meridian curves, and left the radius at 20 mm.
	Parallel angular limits are comprised within the -90° and 90° range. Meridian angular limits are comprised within the -360° and 360° range.
	Click OK to create the surface.
	The spherical surface (identified as Sphere.xxx) is added to the specification tree.
	You can also choose to create a whole sphere. In this case, simply click the icon from the dialog box to generate a complete sphere, based on the center point and the radius. The parallel and meridian angular values are then grayed.