CSPICE_PLTNP finds the nearest point on a triangular plate to a
given point.
For important details concerning this module's function, please refer to
the CSPICE routine pltnp_c.
Given:
point is an arbitrary point in 3dimensional space.
v1,
v2,
v3 are 3vectors 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.
the call:
cspice_pltnp, point, v1, v2, v3, pnear, dist
returns:
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'.
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.
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.
PRO PLTNP_T
point = [2.D, 2.0, 2.0]
v1 = [1.D, 0.0, 0.0]
v2 = [0.D, 1.0, 0.0]
v3 = [0.D, 0.0, 1.0]
cspice_pltnp, point, v1, v2, v3, pnear, dist
print, 'Plate vertex 1 = ', v1
print, 'Plate vertex 2 = ', v2
print, 'Plate vertex 3 = ', v3
print, 'Input point = ', point
print
print, 'Near point = ', pnear
print, 'Distance = ', dist
END
IDL outputs:
Plate vertex 1 = 1.0000000 0.0000000 0.0000000
Plate vertex 2 = 0.0000000 1.0000000 0.0000000
Plate vertex 3 = 0.0000000 0.0000000 1.0000000
Input point = 2.0000000 2.0000000 2.0000000
Near point = 0.33333333 0.33333333 0.33333333
Distance = 2.8867513
None.
ICY.REQ
DSK.REQ
Icy Version 1.0.0, 15DEC2016, ML (JPL), EDW (JPL)
nearest point on triangular plate
