pltar_c |

Table of contents## Procedurepltar_c ( Compute area of plate set ) SpiceDouble pltar_c ( SpiceInt nv, ConstSpiceDouble vrtces [][3], SpiceInt np, ConstSpiceInt plates [][3] ) ## AbstractCompute the total area of a collection of triangular plates. ## Required_ReadingDSK ## KeywordsDSK GEOMETRY MATH TOPOGRAPHY ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- nv I Number of vertices. vrtces I Array of vertices. np I Number of triangular plates. plates I Array of plates. The function returns the total area of the set of plates. ## Detailed_Inputnv is the number of vertices comprising the plate set. vrtces is an array containing the plate model's vertices. Elements vrtces[i-1][0] vrtces[i-1][1] vrtces[i-1][2] are, respectively, the X, Y, and Z components of the ith vertex, where i ranges from 1 to `nv'. This routine doesn't associate units with the vertices. np is the number of triangular plates comprising the plate set. plates is an array containing 3-tuples of integers representing the set of plates. The elements of `plates' are vertex indices. The vertex indices are 1-based: vertices have indices ranging from 1 to `nv'. The elements plates[i-1][0] plates[i-1][1] plates[i-1][2] are, respectively, the indices of the vertices comprising the ith plate. Note that the order of the vertices of a plate is significant: the vertices must be ordered in the positive (counterclockwise) sense with respect to the outward normal direction associated with the plate. In other words, if V1, V2, V3 are the vertices of a plate, then ( V2 - V1 ) x ( V3 - V2 ) points in the outward normal direction. Here "x" denotes the vector cross product operator. ## Detailed_OutputThe function returns the total area of the input set of plates. Each plate contributes the area of the triangle defined by the plate's vertices. If the components of the vertex array have length unit L, then the output area has units 2 L ## ParametersNone. ## Exceptions1) If the number of plates is less than 0, the error SPICE(BADPLATECOUNT) is signaled by a routine in the call tree of this routine. 2) If the number of plates is positive and the number of vertices is less than 3, the error SPICE(TOOFEWVERTICES) is signaled by a routine in the call tree of this routine. 3) If any plate contains a vertex index outside of the range [1, nv] the error SPICE(INDEXOUTOFRANGE) is signaled by a routine in the call tree of this routine. ## FilesNone. ## ParticularsThis routine computes the total area of a set of triangular plates. The plates need not define a closed surface. Examples of valid plate sets: Tetrahedron Box Tiled ellipsoid Tiled ellipsoid with one plate removed Two disjoint boxes Two boxes with intersection having positive volume Single plate Empty plate set ## ExamplesThe numerical results shown for this example 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) Compute the area of the pyramid defined by the four triangular plates whose vertices are the 3-element subsets of the set of vectors: ( 0, 0, 0 ) ( 1, 0, 0 ) ( 0, 1, 0 ) ( 0, 0, 1 ) Example code begins here. /. Program pltar_ex1 Compute the area of a plate model representing the pyramid with one vertex at the origin and the other vertices coinciding with the standard basis vectors. ./ #include <stdio.h> #include "SpiceUsr.h" int main() { /. Local constants ./ #define NVERT 4 #define NPLATE 4 /. Local variables ./ SpiceDouble area; /. Let the notation < A, B > denote the dot product of vectors A and B. The plates defined below lie in the following planes, respectively: Plate 1: { P : < P, (-1, 0, 0) > = 0 } Plate 2: { P : < P, ( 0, -1, 0) > = 0 } Plate 3: { P : < P, ( 0, 0, -1) > = 0 } Plate 4: { P : < P, ( 1, 1, 1) > = 1 } ./ SpiceDouble vrtces[NVERT ][3] = { { 0.0, 0.0, 0.0 }, { 1.0, 0.0, 0.0 }, { 0.0, 1.0, 0.0 }, { 0.0, 0.0, 1.0 } }; SpiceInt plates[NPLATE][3] = { { 1, 4, 3 }, { 1, 2, 4 }, { 1, 3, 2 }, { 2, 3, 4 } }; area = ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) ## Version-CSPICE Version 1.0.1, 04-AUG-2021 (JDR) Edited the header to comply with NAIF standard. -CSPICE Version 1.0.0, 24-OCT-2016 (NJB) ## Index_Entriescompute plate model area |

Fri Dec 31 18:41:10 2021