pl2psv_c |

Table of contents## Procedurepl2psv_c ( Plane to point and spanning vectors ) void pl2psv_c ( ConstSpicePlane * plane, SpiceDouble point[3], SpiceDouble span1[3], SpiceDouble span2[3] ) ## AbstractReturn a point and two orthogonal spanning vectors that generate a specified plane. ## Required_ReadingPLANES ## KeywordsGEOMETRY MATH PLANE ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- plane I A SPICE plane. point, span1, span2 O A point in the input plane and two vectors spanning the input plane. ## Detailed_Inputplane is a SPICE plane. ## Detailed_Outputpoint, span1, span2 are, respectively, a point and two orthogonal spanning vectors that generate the geometric plane represented by `plane'. The geometric plane is the set of vectors point + s * span1 + t * span2 where `s' and `t' are real numbers. `point' is the closest point in the plane to the origin; this point is always a multiple of the plane's normal vector. `span1' and `span2' are an orthonormal pair of vectors. `point', `span1', and `span2' are mutually orthogonal. ## ParametersNone. ## ExceptionsError 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. ## FilesNone. ## ParticularsCSPICE geometry routines that deal with planes use the `plane' data type to represent input and output planes. This data type makes the routine interfaces simpler and more uniform. The CSPICE routines that produce SPICE 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 SPICE planes to data that define a plane are: pl2nvc_c ( Plane to normal vector and constant ) pl2nvp_c ( Plane to normal vector and point ) ## Examples1) Project a vector `v' orthogonally onto a plane defined by `point', `span1', and `span2'. `proj' is the projection we want; it is the closest vector in the plane to `v'. psv2pl_c ( point, span1, span2, &plane ); vprjp_c ( &v, &plane, &proj ); 2) Find the intersection of a plane and the unit sphere. This is a geometry problem that arises in computing the intersection of a plane and a triaxial ellipsoid. The CSPICE routine inedpl_c computes this intersection, but this example does illustrate how to use this routine. /. The geometric plane of interest will be represented by the SPICE plane plane in this example. The intersection circle will be represented by the vectors center, v1, and v2; the circle is the set of points center + cos(theta) v1 + sin(theta) v2, where theta is in the interval (-pi, pi]. The logical variable found indicates whether the intersection is non-empty. The center of the intersection circle will be the closest point in the plane to the origin. This point is returned by ## RestrictionsNone. ## Literature_References[1] G. Thomas and R. Finney, "Calculus and Analytic Geometry," 7th Edition, Addison Wesley, 1988. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) ## Version-CSPICE Version 1.0.1, 24-AUG-2021 (JDR) Edited the header to comply with NAIF standard. Added example #1. -CSPICE Version 1.0.0, 05-MAR-1999 (NJB) ## Index_Entriesplane to point and spanning vectors |

Fri Dec 31 18:41:10 2021