Procedure

   void pl2nvp_c ( ConstSpicePlane   * plane,
                   SpiceDouble         normal[3],
                   SpiceDouble         point [3]  ) 

Abstract

 
   Return a unit normal vector and point that define a specified 
   plane. 
 

Required_Reading

 
   PLANES 
 

Keywords

 
   GEOMETRY 
   MATH 
   PLANE 
 

Brief_I/O

 
   Variable  I/O  Description 
   --------  ---  -------------------------------------------------- 
   plane      I   A CSPICE plane. 
   normal, 
   point      O   A unit normal vector and point that define plane. 
 

Detailed_Input

 
   plane          is a CSPICE plane. 
 

Detailed_Output

 
   normal, 
   point          are, respectively, a unit normal vector and point 
                  that define the geometric plane represented by 
                  plane.  Let the symbol < a, b > indicate the inner 
                  product of vectors a and b; then the geometric 
                  plane is the set of vectors x in three-dimensional 
                  space that satisfy 
 
                     < x - point, normal >  =  0. 
 
                  point is always the closest point in the input 
                  plane to the origin.  point is always a 
                  non-negative scalar multiple of normal. 
 

Parameters

 
   None. 
 

Exceptions

 
   Error free. 
 
   1)  The input plane MUST have been created by one of the CSPICE 
       routines 
 
          nvc2pl_c ( Normal vector and constant to plane ) 
          nvp2pl_c ( Normal vector and point to plane    ) 
          psv2pl_c ( Point and spanning vectors to plane ) 
 
       Otherwise, the results of this routine are unpredictable. 
 

Files

 
   None. 
 

Particulars

 
   CSPICE geometry routines that deal with planes use the `plane' 
   data type to represent input and output planes.  This data type 
   makes the subroutine interfaces simpler and more uniform. 
 
   The CSPICE routines that produce CSPICE planes from data that 
   define a plane are: 
 
      nvc2pl_c ( Normal vector and constant to plane ) 
      nvp2pl_c ( Normal vector and point to plane    ) 
      psv2pl_c ( Point and spanning vectors to plane ) 
 
   The CSPICE routines that convert CSPICE planes to data that 
   define a plane are: 
 
      pl2nvc_c ( Plane to normal vector and constant ) 
      pl2nvp_c ( Plane to normal vector and point    ) 
      pl2psv_c ( Plane to point and spanning vectors ) 
 

Examples

 
   1)  Given a plane normal and constant, find a point in 
       the plane.  point is the point we seek. 
 
          nvc2pl_c ( normal, const,  &plane );
          pl2nvp_c ( &plane, normal, point  ); 
 

Restrictions

 
   None. 
 

Literature_References

 
   [1] `Calculus and Analytic Geometry', Thomas and Finney. 
 

Author_and_Institution

 
   N.J. Bachman   (JPL) 
 

Version

 
   -CSPICE Version 1.0.0, 05-MAR-1999 (NJB)

Index_Entries

 
   plane to normal vector and point 
 

Link to routine pl2nvp_c source file pl2nvp_c.c