anim3D/src/SphereGO.i3

 Copyright (C) 1993, Digital Equipment Corporation                         
 All rights reserved.                                                      
 See the file COPYRIGHT for a full description.                            
                                                                           
 Created by Marc Najork                                                    
 Last modified on Sun Jun 12 17:21:04 PDT 1994 by najork                   




 A SphereGO.T is a geometric object describing a sphere. 


INTERFACE SphereGO;

IMPORT GO, Point3, PointProp, RealProp, SurfaceGO;

TYPE
  T <: Public;
  Public = SurfaceGO.T OBJECT
  METHODS
    init (prec := 30) : T;
  END;

 sph.init(prec) initializes a new sphere sph, whose surface is composed
   of prec strips of prec triangles,  and returns it. The location and
   radius of the sphere are determined by the two properties Center and
   Radius. 

VAR
  Center : PointProp.Name;
  Radius : RealProp.Name;

 In addition to the properties observed by all \type{GO}{T}'s and
   \type{SurfaceGO}{T}'s, there are two additional properties that
   are observed by SphereGO.T's:


   Center is the name of a property that describes the center of the sphere.
   It associates with a \type{PointProp}{Val}. If no Center property
   is specified, the sphere is centered at the origin.


   Radius is the name of a property that describes the radius of the sphere.
   It associates with a \type{RealProp}{Val}. If no Radius property
   is specified, the sphere has a radius of 1. 




PROCEDURE New (center : Point3.T; radius : REAL; prec := 30) : T;

 New(center,radius,prec) creates a new sphere, whose surface is composed of
   prec strips of prec triangles, and returns it. It also attaches the
   following properties to the new sphere:
   \begin{verbatim}
     (Center,PointProp.NewConst(center))
     (Radius,RealProp.NewConst(radius))
   \end{verbatim}

 The following two procedures provide sugaring to attach
   Center and Radius properties with non-animated
   property values to geometric objects: 


PROCEDURE SetCenter (o : GO.T; center : Point3.T);

 The expression SetCenter(o,p) is equivalent to
   o.setProp(Center.bind(PointProp.NewConst(p)). 

PROCEDURE SetRadius (o : GO.T; radius : REAL);

 The expression SetRadius(o,r)is equivalent to
   o.setProp(Radius.bind(RealProp.NewConst(r))). 

END SphereGO.