source: trunk/MagicSoft/slalib/imxv.c@ 9472

Last change on this file since 9472 was 731, checked in by tbretz, 24 years ago
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1#include "slalib.h"
2#include "slamac.h"
3void slaImxv ( float rm[3][3], float va[3], float vb[3] )
4/*
5** - - - - - - - -
6** s l a I m x v
7** - - - - - - - -
8**
9** Performs the 3-d backward unitary transformation:
10**
11** vector vb = (inverse of matrix rm) * vector va
12**
13** (single precision)
14**
15** n.b. The matrix must be unitary, as this routine assumes that
16** the inverse and transpose are identical.
17**
18** Given:
19** rm float[3][3] matrix
20** va float[3] vector
21**
22** Returned:
23** vb float[3] result vector
24**
25** The same vector can be specified for both va and vb.
26**
27** Last revision: 6 November 1999
28**
29** Copyright P.T.Wallace. All rights reserved.
30*/
31{
32 int i, j;
33 float w, vw[3];
34
35/* Inverse of matrix rm * vector va -> vector vw */
36 for ( j = 0; j < 3; j++ ) {
37 w = 0.0f;
38 for ( i = 0; i < 3; i++ ) {
39 w += rm[i][j] * va[i];
40 }
41 vw[j] = w;
42 }
43
44/* Vector vw -> vector vb */
45 for ( j = 0; j < 3; j++ ) {
46 vb[j] = vw[j];
47 }
48}
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