CSPICE_VPRJPI calculates the vector in a specified plane that
maps under orthogonal projection to a specified vector in
another plane.
For important details concerning this module's function, please refer to
the CSPICE routine vprjpi_c.
Given:
vin a double precision 3vector.
projpl a SPICE plane structure, describing a SPICE plane that
represents the geometric plane containing 'vin'. The structure
has the fields:
normal: [3array double]
constant: [scalar double]
invpl a SPICE plane structure, describing a SPICE plane that
represents the geometric plane containing the inverse image
of 'vin' under orthogonal projection onto 'projpl'.
The structure has the fields:
normal: [3array double]
constant: [scalar double]
the call:
cspice_vprjpi, vin, projpl, invpl, vout, found
returns:
vout the double precision 3vector inverse orthogonal projection
of 'vin'. This is the vector lying in the plane 'invpl' whose
orthogonal projection onto the plane 'projpl' is 'vin'. 'vout'
is valid only when 'found' is true. Otherwise,
'vout' is undefined.
found a scalar boolean flag, indicating whether the inverse orthogonal
projection of 'vin' could be computed. 'found' is true if so,
false otherwise.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
;;
;; Construct two planes via cspice_nvc2pl. Define the normal
;; vectors and constants for the planes.
;;
norm1 = [ 0.d, 0.d, 1.d]
norm2 = [ 1.d, 0.d, 1.d]
con1 = 1.2d
con2 = 0.65d
;;
;; Use the normals and constants to create the plane structures,
;; plane1 and plane2.
;;
cspice_nvc2pl, norm1, con1, plane1
cspice_nvc2pl, norm2, con2, plane2
;;
;; Define a vector in plane1...
;;
vec = [ 1.d, 1.d, 0.d]
;;
;; Calculate the inverse projection to plane2.
;;
cspice_vprjpi, vec, plane1, plane2, vec_iproj, found
if ( found ) then begin
print, 'Found an inverse vector:', vec_iproj
endif else begin
print, 'Could not find the inverse vector.'
endelse
IDL outputs:
Found an inverse vector: 1.0000000 1.0000000 0.35000000
None.
ICY.REQ
Icy Version 1.0.2, 23NOV2010, EDW (JPL)
Edit to example code comments and 'vec' assignment eliminating typos.
Icy Version 1.0.1, 02MAY2005, EDW (JPL)
Corrected typo in description of 'found'.
Icy Version 1.0.0, 16JUN2003, EDW (JPL)
vector projection onto plane inverted
