anim3D/src/TorusGO.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 Mon Jun 13 10:12:34 PDT 1994 by najork                   




 A TorusGO.T is a geometric object describing a torus.
   A torus can be described by one major and an infinite set of minor circles.


   The major circle of the torus is centerest at point center, its radius
   is rad, and its normal vector is normal. The minor circles (which
   together make up the surface of the torus) are centered around the perimeter
   of the mayor circle, their radius is rad2, and their normal vector is
   parallel to the circumference of the major circle in their center point.


   The following picture tries to illustrate the roles of the various
   parameters:
   \begin{center}
   \begin{tabular}{c}
   \psfig{figure=images/TorusGO.ps,width=3in,silent=}
   \end{tabular}
   \end{center} 


INTERFACE TorusGO;

IMPORT GO, Point3, PointProp, RealProp, SurfaceGO;

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

 tor.init(prec) initializes a new torus tor, composed of prec strips
   of prec trapezoids, and returns it.
   The location, orientation, and size of the torus is determined by the
   Center, Normal, Radius1, and Radius2 property values. 

VAR
  Center  : PointProp.Name;
  Normal  : PointProp.Name;
  Radius1 : RealProp.Name;
  Radius2 : RealProp.Name;

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


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


   Normal is the name of a property that describes the normal vector of
   the torus. It associates with a \type{PointProp}{Val}. If no Normal
   property is specified, the normal vector is taken to be (0,0,1).


   Radius1 is the name of a property that describes the radius of the
   major circle of the torus. It associates with a \type{RealProp}{Val}.
   If no Radius1 property is specified, the torus has a major radius of 1.


   Radius2 is the name of a property that describes the radius of the
   minor circle of the torus. It associates with a \type{RealProp}{Val}.
   If no Radius2 property is specified, the torus has a minor radius
   of 0.1. 

PROCEDURE New (center, normal   : Point3.T;
               radius1, radius2 : REAL;
               prec := 30) : T;

 New(center,normal,radius1, radius2,prec) creates a new torus,
   whose surface is composed of prec strips of prec trapezoids,
   and returns it. It also attaches the following properties
   to the new torus:
   \begin{verbatim}
     (Center,PointProp.NewConst(center))
     (Normal,PointProp.NewConst(normal))
     (Radius1,RealProp.NewConst(rad1))
     (Radius2,RealProp.NewConst(rad2))
   \end{verbatim} 
 The following three procedures provide sugaring to attach Center,
   Normal, Radius1, and Radius2 properties (where the property
   values have constant behaviors) to geometric objects: 


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

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

PROCEDURE SetNormal (o : GO.T; p : Point3.T);

 The expression SetNormal(o,p) is equivalent to
   o.setProp(Normal.bind(PointProp.NewConst(p))). 

PROCEDURE SetRadius1 (o : GO.T; r : REAL);

 The expression SetRadius1(o,r)is equivalent to
   o.setProp(Radius1.bind(RealProp.NewConst(r))). 

PROCEDURE SetRadius2 (o : GO.T; r : REAL);

 The expression SetRadius2(o,r)is equivalent to
   o.setProp(Radius2.bind(RealProp.NewConst(r))). 

END TorusGO.