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pltnp_c
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Procedure
Abstract
Required_Reading
Keywords
Brief_I/O
Detailed_Input
Detailed_Output
Parameters
Exceptions
Files
Particulars
Examples
Restrictions
Literature_References
Author_and_Institution
Version
Index_Entries

Procedure

   void pltnp_c ( ConstSpiceDouble    point[3],
                  ConstSpiceDouble    v1   [3],
                  ConstSpiceDouble    v2   [3],
                  ConstSpiceDouble    v3   [3],
                  SpiceDouble         pnear[3],
                  SpiceDouble       * dist      ) 

Abstract

 
   Find the nearest point on a triangular plate to a given point. 
 

Required_Reading

 
   None. 
 

Keywords

 
   GEOMETRY 
   MATH 
 

Brief_I/O

 
   Variable  I/O  Description 
   --------  ---  -------------------------------------------------- 
   point      I   A point in 3-dimensional space. 
   v1, 
   v2, 
   v3         I   Vertices of a triangular plate. 
   pnear      O   Nearest point on the plate to `point'. 
   dist       O   Distance between `pnear' and `point'. 
 

Detailed_Input

 
   point      is an arbitrary point in 3-dimensional space. 
 
   v1, 
   v2, 
   v3         are 3-vectors constituting the vertices of  
              a triangular plate. 
 
              The plate is allowed to be degenerate: it may 
              consist of a line segment or of a single point. 
         

Detailed_Output

 
   pnear      is the closest point on the plate to `point'. 
              `pnear' is unique, since the plate is convex. 
 
   dist       is the distance between `point' and `pnear'. 
 

Parameters

 
   None. 
 

Exceptions

 
   1) The input plate is allowed to be degenerate: it may be 
      a line segment or a single point. 
 

Files

 
   None. 
 

Particulars

 
   None. 
 

Examples

 
   The numerical results shown for these examples may differ across 
   platforms. The results depend on the SPICE kernels used as input 
   (if any), the compiler and supporting libraries, and the machine 
   specific arithmetic implementation. 
 
 
   1) Find the nearest point to the point (2,2,2) on a plate having 
      vertices at the unit basis vectors that lie along the positive 
      X, Y, and Z coordinate axes. 
 
 
      Example code begins here.  
  

         #include <stdio.h>
         #include "SpiceUsr.h"

         int main()
         {
            /.
            Local variables 
            ./ 
            SpiceDouble             dist;
            SpiceDouble             pnear[3];
            SpiceDouble             point[3] = {2.0, 2.0, 2.0};
            SpiceDouble             v1   [3] = {1.0, 0.0, 0.0};
            SpiceDouble             v2   [3] = {0.0, 1.0, 0.0};
            SpiceDouble             v3   [3] = {0.0, 0.0, 1.0};

            pltnp_c ( point, v1, v2, v3, pnear, &dist );

            printf ( "\n"
                     "Plate vertex 1 = %14.7e %14.7e %14.7e\n" 
                     "Plate vertex 2 = %14.7e %14.7e %14.7e\n" 
                     "Plate vertex 3 = %14.7e %14.7e %14.7e\n" 
                     "Input point    = %14.7e %14.7e %14.7e\n" 
                     "\n"
                     "Near point     = %14.7e %14.7e %14.7e\n" 
                     "Distance       = %14.7e\n" 
                     "\n",
                     v1[0],    v1[1],    v1[2],
                     v2[0],    v2[1],    v2[2],
                     v3[0],    v3[1],    v3[2],
                     point[0], point[1], point[2],
                     pnear[0], pnear[1], pnear[2],
                     dist                                    );

            return ( 0 );
         }
 
 
   When this program was executed on a PC/Linux/gcc/64-bit platform, 
   the output was: 


      Plate vertex 1 =  1.0000000e+00  0.0000000e+00  0.0000000e+00
      Plate vertex 2 =  0.0000000e+00  1.0000000e+00  0.0000000e+00
      Plate vertex 3 =  0.0000000e+00  0.0000000e+00  1.0000000e+00
      Input point    =  2.0000000e+00  2.0000000e+00  2.0000000e+00

      Near point     =  3.3333333e-01  3.3333333e-01  3.3333333e-01
      Distance       =  2.8867513e+00

 

Restrictions

 
   None. 
 

Literature_References

 
   None. 
 

Author_and_Institution

 
   N.J. Bachman   (JPL) 
 

Version

 
   -CSPICE Version 1.0.0, 1-FEB-2016 (NJB)

Index_Entries

 
   nearest point on triangular plate 
 
Wed Apr  5 17:54:40 2017