LORENE
scalar_import_symy.C
1 /*
2  * Member function of the Scalar class for initiating a Scalar from
3  * a Scalar defined on another mapping.
4  * Case where both Scalar's are symmetric with respect to their y=0 plane.
5  */
6 
7 /*
8  * Copyright (c) 2003 Eric Gourgoulhon & Jerome Novak
9  * Copyright (c) 1999-2001 Eric Gourgoulhon (Cmp version)
10  *
11  * This file is part of LORENE.
12  *
13  * LORENE is free software; you can redistribute it and/or modify
14  * it under the terms of the GNU General Public License as published by
15  * the Free Software Foundation; either version 2 of the License, or
16  * (at your option) any later version.
17  *
18  * LORENE is distributed in the hope that it will be useful,
19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21  * GNU General Public License for more details.
22  *
23  * You should have received a copy of the GNU General Public License
24  * along with LORENE; if not, write to the Free Software
25  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26  *
27  */
28 
29 
30 
31 
32 
33 /*
34  * $Id: scalar_import_symy.C,v 1.6 2016/12/05 16:18:18 j_novak Exp $
35  * $Log: scalar_import_symy.C,v $
36  * Revision 1.6 2016/12/05 16:18:18 j_novak
37  * Suppression of some global variables (file names, loch, ...) to prevent redefinitions
38  *
39  * Revision 1.5 2014/10/13 08:53:46 j_novak
40  * Lorene classes and functions now belong to the namespace Lorene.
41  *
42  * Revision 1.4 2014/10/06 15:16:15 j_novak
43  * Modified #include directives to use c++ syntax.
44  *
45  * Revision 1.3 2003/10/10 15:57:29 j_novak
46  * Added the state one (ETATUN) to the class Scalar
47  *
48  * Revision 1.2 2003/10/01 13:04:44 e_gourgoulhon
49  * The method Tensor::get_mp() returns now a reference (and not
50  * a pointer) onto a mapping.
51  *
52  * Revision 1.1 2003/09/25 09:07:05 j_novak
53  * Added the functions for importing from another mapping (to be tested).
54  *
55  *
56  * $Header: /cvsroot/Lorene/C++/Source/Tensor/Scalar/scalar_import_symy.C,v 1.6 2016/12/05 16:18:18 j_novak Exp $
57  *
58  */
59 
60 
61 
62 // Headers C
63 #include <cmath>
64 
65 // Headers Lorene
66 #include "tensor.h"
67 #include "param.h"
68 #include "nbr_spx.h"
69 
70  //-------------------------------//
71  // Importation in all domains //
72  //-------------------------------//
73 
74 namespace Lorene {
75 void Scalar::import_symy(const Scalar& ci) {
76 
77  int nz = mp->get_mg()->get_nzone() ;
78 
79  import_symy(nz, ci) ;
80 
81 }
82 
83  //--------------------------------------//
84  // Importation in inner domains only //
85  //--------------------------------------//
86 
87 void Scalar::import_symy(int nzet, const Scalar& cm_d) {
88 
89  const Map* mp_d = &(cm_d.get_mp()) ; // Departure mapping
90 
91  // Trivial case : mappings identical !
92  // -----------------------------------
93 
94  if (mp_d == mp) {
95  *this = cm_d ;
96  return ;
97  }
98 
99  // Relative orientation of the two mappings
100  // ----------------------------------------
101 
102  int align_rel = (mp->get_bvect_cart()).get_align()
103  * (mp_d->get_bvect_cart()).get_align() ;
104 
105  switch (align_rel) {
106 
107  case 1 : { // the two mappings have aligned Cartesian axis
108  import_align_symy(nzet, cm_d) ;
109  break ;
110  }
111 
112  case -1 : { // the two mappings have anti-aligned Cartesian axis
113  import_anti_symy(nzet, cm_d) ;
114  break ;
115  }
116 
117  default : {
118  cout << "Scalar::import_symy : unexpected value of align_rel : "
119  << align_rel << endl ;
120  abort() ;
121  break ;
122  }
123 
124  }
125 
126 }
127 
128 
129  //-----------------------------------------//
130  // Case of Cartesian axis anti-aligned //
131  //-----------------------------------------//
132 
133 
134 void Scalar::import_anti_symy(int nzet, const Scalar& cm_d) {
135 
136  // Trivial case : null Scalar
137  // ------------------------
138 
139  if (cm_d.get_etat() == ETATZERO) {
140  set_etat_zero() ;
141  return ;
142  }
143  if (cm_d.get_etat() == ETATUN) {
144  set_etat_one() ;
145  return ;
146  }
147 
148  const Map* mp_d = &(cm_d.get_mp()) ; // Departure mapping
149 
150  // Protections
151  // -----------
152  int align = (mp->get_bvect_cart()).get_align() ;
153 
154  assert( align * (mp_d->get_bvect_cart()).get_align() == -1 ) ;
155 
156  assert(cm_d.get_etat() == ETATQCQ) ;
157 
158  if (cm_d.get_dzpuis() != 0) {
159  cout <<
160  "Scalar::import_anti_symy : the dzpuis of the Scalar to be imported"
161  << " must be zero !" << endl ;
162  abort() ;
163  }
164 
165 
166  const Mg3d* mg_a = mp->get_mg() ;
167  assert(mg_a->get_type_p() == NONSYM) ;
168 
169  int nz_a = mg_a->get_nzone() ;
170  assert(nzet <= nz_a) ;
171 
172  const Valeur& va_d = cm_d.get_spectral_va() ;
173  va_d.coef() ; // The coefficients are required
174 
175 
176  // Preparations for storing the result in *this
177  // --------------------------------------------
178  del_t() ; // delete all previously computed derived quantities
179 
180  set_etat_qcq() ; // Set the state to ETATQCQ
181 
182  va.set_etat_c_qcq() ; // Allocates the memory for the Mtbl va.c
183  // if it does not exist already
184  va.c->set_etat_qcq() ; // Allocates the memory for the Tbl's in each
185  // domain if they do not exist already
186 
187 
188  // Departure (x,y,z) coordinates of the origin of the Arrival mapping :
189 
190  double xx_a, yy_a, zz_a ;
191  if (align == 1) {
192  xx_a = mp_d->get_ori_x() - mp->get_ori_x() ;
193  yy_a = mp_d->get_ori_y() - mp->get_ori_y() ;
194  }
195  else {
196  xx_a = mp->get_ori_x() - mp_d->get_ori_x() ;
197  yy_a = mp->get_ori_y() - mp_d->get_ori_y() ;
198  }
199  zz_a = mp->get_ori_z() - mp_d->get_ori_z() ;
200 
201 
202  // r, theta, phi, x, y and z on the Arrival mapping
203  // update of the corresponding Coord's if necessary
204 
205  if ( (mp->r).c == 0x0 ) (mp->r).fait() ;
206  if ( (mp->tet).c == 0x0 ) (mp->tet).fait() ;
207  if ( (mp->phi).c == 0x0 ) (mp->phi).fait() ;
208  if ( (mp->x).c == 0x0 ) (mp->x).fait() ;
209  if ( (mp->y).c == 0x0 ) (mp->y).fait() ;
210  if ( (mp->z).c == 0x0 ) (mp->z).fait() ;
211 
212  const Mtbl* mr_a = (mp->r).c ;
213  const Mtbl* mtet_a = (mp->tet).c ;
214  const Mtbl* mphi_a = (mp->phi).c ;
215  const Mtbl* mx_a = (mp->x).c ;
216  const Mtbl* my_a = (mp->y).c ;
217  const Mtbl* mz_a = (mp->z).c ;
218 
219  Param par_precis ; // Required precision in the method Map::val_lx
220  int nitermax = 100 ; // Maximum number of iteration in the secant method
221  int niter ;
222  double precis = 1e-15 ; // Absolute precision in the secant method
223  par_precis.add_int(nitermax) ;
224  par_precis.add_int_mod(niter) ;
225  par_precis.add_double(precis) ;
226 
227 
228  // Loop of the Arrival domains where the computation is to be performed
229  // --------------------------------------------------------------------
230 
231  for (int l=0; l < nzet; l++) {
232 
233  int nr = mg_a->get_nr(l) ;
234  int nt = mg_a->get_nt(l) ;
235  int np = mg_a->get_np(l) ;
236 
237 
238  const double* pr_a = mr_a->t[l]->t ; // Pointer on the values of r
239  const double* ptet_a = mtet_a->t[l]->t ; // Pointer on the values of theta
240  const double* pphi_a = mphi_a->t[l]->t ; // Pointer on the values of phi
241  const double* px_a = mx_a->t[l]->t ; // Pointer on the values of X
242  const double* py_a = my_a->t[l]->t ; // Pointer on the values of Y
243  const double* pz_a = mz_a->t[l]->t ; // Pointer on the values of Z
244 
245  (va.c->t[l])->set_etat_qcq() ; // Allocates the array of double to
246  // store the result
247  double* ptx = (va.c->t[l])->t ; // Pointer on the allocated array
248 
249 
250  // Loop on half the grid points in the considered arrival domain
251  // (the other half will be obtained by symmetry with respect to
252  // the y=0 plane).
253 
254  for (int k=0 ; k<np/2+1 ; k++) { // np/2+1 : half the grid
255  for (int j=0 ; j<nt ; j++) {
256  for (int i=0 ; i<nr ; i++) {
257 
258  double r = *pr_a ;
259  double rd, tetd, phid ;
260  if (r == __infinity) {
261  rd = r ;
262  tetd = *ptet_a ;
263  phid = *pphi_a + M_PI ;
264  if (phid < 0) phid += 2*M_PI ;
265  }
266  else {
267 
268  // Cartesian coordinates on the Departure mapping
269  double xd = - *px_a + xx_a ;
270  double yd = - *py_a + yy_a ;
271  double zd = *pz_a + zz_a ;
272 
273  // Spherical coordinates on the Departure mapping
274  double rhod2 = xd*xd + yd*yd ;
275  double rhod = sqrt( rhod2 ) ;
276  rd = sqrt(rhod2 + zd*zd) ;
277  tetd = atan2(rhod, zd) ;
278  phid = atan2(yd, xd) ;
279  if (phid < 0) phid += 2*M_PI ;
280  }
281 
282 
283  // NB: to increase the efficiency, the method Scalar::val_point
284  // is not invoked; the method Mtbl_cf::val_point is
285  // called directly instead.
286 
287  // Value of the grid coordinates (l,xi) corresponding to
288  // (rd,tetd,phid) :
289 
290  int ld ; // domain index
291  double xxd ; // radial coordinate xi in [0,1] or [-1,1]
292  mp_d->val_lx(rd, tetd, phid, par_precis, ld, xxd) ;
293 
294  // Value of the Departure Scalar at the obtained point:
295  *ptx = va_d.c_cf->val_point_symy(ld, xxd, tetd, phid) ;
296 
297  // Next point :
298  ptx++ ;
299  pr_a++ ;
300  ptet_a++ ;
301  pphi_a++ ;
302  px_a++ ;
303  py_a++ ;
304  pz_a++ ;
305 
306  }
307  }
308  }
309 
310  // The remaining points are obtained by symmetry with rspect to the
311  // y=0 plane
312 
313  for (int k=np/2+1 ; k<np ; k++) {
314 
315  // pointer on the value (already computed) at the point symmetric
316  // with respect to the plane y=0
317  double* ptx_symy = (va.c->t[l])->t + (np-k)*nt*nr ;
318 
319  // copy :
320  for (int j=0 ; j<nt ; j++) {
321  for (int i=0 ; i<nr ; i++) {
322  *ptx = *ptx_symy ;
323  ptx++ ;
324  ptx_symy++ ;
325  }
326  }
327  }
328 
329 
330  } // End of the loop on the Arrival domains
331 
332  // In the remaining domains, *this is set to zero:
333  // ----------------------------------------------
334 
335  if (nzet < nz_a) {
336  annule(nzet, nz_a - 1) ;
337  }
338 
339  // Treatment of dzpuis
340  // -------------------
341 
342  set_dzpuis(0) ;
343 
344 }
345 
346 
347  //-------------------------------------//
348  // Case of aligned Cartesian axis //
349  //-------------------------------------//
350 
351 
352 void Scalar::import_align_symy(int nzet, const Scalar& cm_d) {
353 
354  // Trivial case : null Scalar
355  // ------------------------
356 
357  if (cm_d.get_etat() == ETATZERO) {
358  set_etat_zero() ;
359  return ;
360  }
361  if (cm_d.get_etat() == ETATUN) {
362  set_etat_one() ;
363  return ;
364  }
365 
366  const Map* mp_d = &(cm_d.get_mp()) ; // Departure mapping
367 
368  // Protections
369  // -----------
370  int align = (mp->get_bvect_cart()).get_align() ;
371 
372  assert( align * (mp_d->get_bvect_cart()).get_align() == 1 ) ;
373 
374  assert(cm_d.get_etat() == ETATQCQ) ;
375 
376  if (cm_d.get_dzpuis() != 0) {
377  cout <<
378  "Scalar::import_align_symy : the dzpuis of the Scalar to be imported"
379  << " must be zero !" << endl ;
380  abort() ;
381  }
382 
383 
384  const Mg3d* mg_a = mp->get_mg() ;
385  assert(mg_a->get_type_p() == NONSYM) ;
386 
387  int nz_a = mg_a->get_nzone() ;
388  assert(nzet <= nz_a) ;
389 
390  const Valeur& va_d = cm_d.get_spectral_va() ;
391  va_d.coef() ; // The coefficients are required
392 
393 
394  // Preparations for storing the result in *this
395  // --------------------------------------------
396  del_t() ; // delete all previously computed derived quantities
397 
398  set_etat_qcq() ; // Set the state to ETATQCQ
399 
400  va.set_etat_c_qcq() ; // Allocates the memory for the Mtbl va.c
401  // if it does not exist already
402  va.c->set_etat_qcq() ; // Allocates the memory for the Tbl's in each
403  // domain if they do not exist already
404 
405 
406  // Departure (x,y,z) coordinates of the origin of the Arrival mapping :
407 
408  double xx_a, yy_a, zz_a ;
409  if (align == 1) {
410  xx_a = mp->get_ori_x() - mp_d->get_ori_x() ;
411  yy_a = mp->get_ori_y() - mp_d->get_ori_y() ;
412  }
413  else {
414  xx_a = mp_d->get_ori_x() - mp->get_ori_x() ;
415  yy_a = mp_d->get_ori_y() - mp->get_ori_y() ;
416  }
417  zz_a = mp->get_ori_z() - mp_d->get_ori_z() ;
418 
419 
420  // r, theta, phi, x, y and z on the Arrival mapping
421  // update of the corresponding Coord's if necessary
422 
423  if ( (mp->r).c == 0x0 ) (mp->r).fait() ;
424  if ( (mp->tet).c == 0x0 ) (mp->tet).fait() ;
425  if ( (mp->phi).c == 0x0 ) (mp->phi).fait() ;
426  if ( (mp->x).c == 0x0 ) (mp->x).fait() ;
427  if ( (mp->y).c == 0x0 ) (mp->y).fait() ;
428  if ( (mp->z).c == 0x0 ) (mp->z).fait() ;
429 
430  const Mtbl* mr_a = (mp->r).c ;
431  const Mtbl* mtet_a = (mp->tet).c ;
432  const Mtbl* mphi_a = (mp->phi).c ;
433  const Mtbl* mx_a = (mp->x).c ;
434  const Mtbl* my_a = (mp->y).c ;
435  const Mtbl* mz_a = (mp->z).c ;
436 
437  Param par_precis ; // Required precision in the method Map::val_lx
438  int nitermax = 100 ; // Maximum number of iteration in the secant method
439  int niter ;
440  double precis = 1e-15 ; // Absolute precision in the secant method
441  par_precis.add_int(nitermax) ;
442  par_precis.add_int_mod(niter) ;
443  par_precis.add_double(precis) ;
444 
445 
446  // Loop of the Arrival domains where the computation is to be performed
447  // --------------------------------------------------------------------
448 
449  for (int l=0; l < nzet; l++) {
450 
451  int nr = mg_a->get_nr(l) ;
452  int nt = mg_a->get_nt(l) ;
453  int np = mg_a->get_np(l) ;
454 
455 
456  const double* pr_a = mr_a->t[l]->t ; // Pointer on the values of r
457  const double* ptet_a = mtet_a->t[l]->t ; // Pointer on the values of theta
458  const double* pphi_a = mphi_a->t[l]->t ; // Pointer on the values of phi
459  const double* px_a = mx_a->t[l]->t ; // Pointer on the values of X
460  const double* py_a = my_a->t[l]->t ; // Pointer on the values of Y
461  const double* pz_a = mz_a->t[l]->t ; // Pointer on the values of Z
462 
463  (va.c->t[l])->set_etat_qcq() ; // Allocates the array of double to
464  // store the result
465  double* ptx = (va.c->t[l])->t ; // Pointer on the allocated array
466 
467 
468 
469  // Loop on half the grid points in the considered arrival domain
470  // (the other half will be obtained by symmetry with respect to
471  // the y=0 plane).
472 
473  for (int k=0 ; k<np/2+1 ; k++) { // np/2+1 : half the grid
474  for (int j=0 ; j<nt ; j++) {
475  for (int i=0 ; i<nr ; i++) {
476 
477  double r = *pr_a ;
478  double rd, tetd, phid ;
479  if (r == __infinity) {
480  rd = r ;
481  tetd = *ptet_a ;
482  phid = *pphi_a ;
483  }
484  else {
485 
486  // Cartesian coordinates on the Departure mapping
487  double xd = *px_a + xx_a ;
488  double yd = *py_a + yy_a ;
489  double zd = *pz_a + zz_a ;
490 
491  // Spherical coordinates on the Departure mapping
492  double rhod2 = xd*xd + yd*yd ;
493  double rhod = sqrt( rhod2 ) ;
494  rd = sqrt(rhod2 + zd*zd) ;
495  tetd = atan2(rhod, zd) ;
496  phid = atan2(yd, xd) ;
497  if (phid < 0) phid += 2*M_PI ;
498  }
499 
500 
501  // NB: to increase the efficiency, the method Scalar::val_point
502  // is not invoked; the method Mtbl_cf::val_point is
503  // called directly instead.
504 
505  // Value of the grid coordinates (l,xi) corresponding to
506  // (rd,tetd,phid) :
507 
508  int ld ; // domain index
509  double xxd ; // radial coordinate xi in [0,1] or [-1,1]
510  mp_d->val_lx(rd, tetd, phid, par_precis, ld, xxd) ;
511 
512  // Value of the Departure Scalar at the obtained point:
513  *ptx = va_d.c_cf->val_point_symy(ld, xxd, tetd, phid) ;
514 
515  // Next point :
516  ptx++ ;
517  pr_a++ ;
518  ptet_a++ ;
519  pphi_a++ ;
520  px_a++ ;
521  py_a++ ;
522  pz_a++ ;
523 
524  }
525  }
526  }
527 
528 
529  // The remaining points are obtained by symmetry with rspect to the
530  // y=0 plane
531 
532  for (int k=np/2+1 ; k<np ; k++) {
533 
534  // pointer on the value (already computed) at the point symmetric
535  // with respect to the plane y=0
536  double* ptx_symy = (va.c->t[l])->t + (np-k)*nt*nr ;
537 
538  // copy :
539  for (int j=0 ; j<nt ; j++) {
540  for (int i=0 ; i<nr ; i++) {
541  *ptx = *ptx_symy ;
542  ptx++ ;
543  ptx_symy++ ;
544  }
545  }
546  }
547 
548  } // End of the loop on the Arrival domains
549 
550  // In the remaining domains, *this is set to zero:
551  // ----------------------------------------------
552 
553  if (nzet < nz_a) {
554  annule(nzet, nz_a - 1) ;
555  }
556 
557  // Treatment of dzpuis
558  // -------------------
559 
560  set_dzpuis(0) ;
561 
562 }
563 }
int get_type_p() const
Returns the type of sampling in the direction: SYM : : symmetry with respect to the transformatio...
Definition: grilles.h:512
Mtbl_cf * c_cf
Coefficients of the spectral expansion of the function.
Definition: valeur.h:312
void add_int(const int &n, int position=0)
Adds the address of a new int to the list.
Definition: param.C:249
int get_np(int l) const
Returns the number of points in the azimuthal direction ( ) in domain no. l.
Definition: grilles.h:479
void coef() const
Computes the coeffcients of *this.
Definition: valeur_coef.C:151
virtual void set_etat_zero()
Sets the logical state to ETATZERO (zero).
Definition: scalar.C:330
virtual void annule(int l_min, int l_max)
Sets the Scalar to zero in several domains.
Definition: scalar.C:397
Multi-domain array.
Definition: mtbl.h:118
double get_ori_y() const
Returns the y coordinate of the origin.
Definition: map.h:788
Lorene prototypes.
Definition: app_hor.h:67
const Mg3d * get_mg() const
Gives the Mg3d on which the mapping is defined.
Definition: map.h:783
Tensor field of valence 0 (or component of a tensorial field).
Definition: scalar.h:393
Base class for coordinate mappings.
Definition: map.h:688
double get_ori_x() const
Returns the x coordinate of the origin.
Definition: map.h:786
void import_anti_symy(int nzet, const Scalar &ci)
Assignment to another Scalar defined on a different mapping, when the two mappings have anti-aligned ...
Values and coefficients of a (real-value) function.
Definition: valeur.h:297
int get_etat() const
Returns the logical state ETATNONDEF (undefined), ETATZERO (null) or ETATQCQ (ordinary).
Definition: scalar.h:560
virtual void set_etat_qcq()
Sets the logical state to ETATQCQ (ordinary state).
Definition: scalar.C:359
friend Scalar sqrt(const Scalar &)
Square root.
Definition: scalar_math.C:266
Coord tet
coordinate centered on the grid
Definition: map.h:737
void set_dzpuis(int)
Modifies the dzpuis flag.
Definition: scalar.C:814
Coord phi
coordinate centered on the grid
Definition: map.h:738
int get_dzpuis() const
Returns dzpuis.
Definition: scalar.h:563
double * t
The array of double.
Definition: tbl.h:176
Mtbl * c
Values of the function at the points of the multi-grid.
Definition: valeur.h:309
Parameter storage.
Definition: param.h:125
void set_etat_one()
Sets the logical state to ETATUN (one).
Definition: scalar.C:340
int get_nzone() const
Returns the number of domains.
Definition: grilles.h:465
Valeur va
The numerical value of the Scalar.
Definition: scalar.h:411
void del_t()
Logical destructor.
Definition: scalar.C:285
void set_etat_qcq()
Sets the logical state to ETATQCQ (ordinary state).
Definition: mtbl.C:302
void import_align_symy(int nzet, const Scalar &ci)
Assignment to another Scalar defined on a different mapping, when the two mappings have aligned Carte...
int get_nr(int l) const
Returns the number of points in the radial direction ( ) in domain no. l.
Definition: grilles.h:469
Multi-domain grid.
Definition: grilles.h:279
double val_point_symy(int l, double x, double theta, double phi) const
Computes the value of the field represented by *this at an arbitrary point, by means of the spectral ...
const Base_vect_cart & get_bvect_cart() const
Returns the Cartesian basis associated with the coordinates (x,y,z) of the mapping, i.e.
Definition: map.h:809
Coord y
y coordinate centered on the grid
Definition: map.h:745
void add_double(const double &x, int position=0)
Adds the the address of a new double to the list.
Definition: param.C:318
Coord x
x coordinate centered on the grid
Definition: map.h:744
void import_symy(const Scalar &ci)
Assignment to another Scalar defined on a different mapping.
void set_etat_c_qcq()
Sets the logical state to ETATQCQ (ordinary state) for values in the configuration space (Mtbl c )...
Definition: valeur.C:704
double get_ori_z() const
Returns the z coordinate of the origin.
Definition: map.h:790
int get_nt(int l) const
Returns the number of points in the co-latitude direction ( ) in domain no. l.
Definition: grilles.h:474
const Map *const mp
Mapping on which the numerical values at the grid points are defined.
Definition: tensor.h:301
Tbl ** t
Array (size nzone ) of pointers on the Tbl &#39;s.
Definition: mtbl.h:132
const Map & get_mp() const
Returns the mapping.
Definition: tensor.h:874
Coord z
z coordinate centered on the grid
Definition: map.h:746
void add_int_mod(int &n, int position=0)
Adds the address of a new modifiable int to the list.
Definition: param.C:388
const Valeur & get_spectral_va() const
Returns va (read only version)
Definition: scalar.h:607
Coord r
r coordinate centered on the grid
Definition: map.h:736
virtual void val_lx(double rr, double theta, double pphi, int &l, double &xi) const =0
Computes the domain index l and the value of corresponding to a point given by its physical coordina...