Last change
on this file since 4450 was 731, checked in by tbretz, 24 years ago |
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1 | #include "slalib.h"
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2 | #include "slamac.h"
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3 | void slaDvn ( double v[3], double uv[3], double *vm )
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4 | /*
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5 | ** - - - - - - -
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6 | ** s l a D v n
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7 | ** - - - - - - -
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8 | **
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9 | ** Normalizes a 3-vector also giving the modulus.
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10 | **
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11 | ** (double precision)
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12 | **
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13 | ** Given:
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14 | ** v double[3] vector
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15 | **
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16 | ** Returned:
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17 | ** uv double[3] unit vector in direction of v
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18 | ** *vm double modulus of v
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19 | **
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20 | ** Note: v and uv may be the same array.
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21 | **
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22 | **
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23 | ** If the modulus of v is zero, uv is set to zero as well.
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24 | **
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25 | ** Last revision: 6 November 1999
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26 | **
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27 | ** Copyright P.T.Wallace. All rights reserved.
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28 | */
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29 | {
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30 | int i;
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31 | double w1, w2;
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32 |
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33 | /* Modulus */
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34 | w1 = 0.0;
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35 | for ( i = 0; i < 3; i++ ) {
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36 | w2 = v[i];
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37 | w1 += w2 * w2;
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38 | }
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39 | w1 = sqrt ( w1 );
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40 | *vm = w1;
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41 |
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42 | /* Normalize the vector */
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43 | w1 = ( w1 > 0.0 ) ? w1 : 1.0;
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44 |
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45 | for ( i = 0; i < 3; i++ ) {
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46 | uv[i] = v[i] / w1;
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47 | }
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48 | }
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