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follow.c
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Thu, Jan 2, 21:51

follow.c
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#include<stdio.h>
#include<math.h>
#include<fonction.h>
#include<constant.h>
#include<dimension.h>
#include<structure.h>
/****************************************************************/
/* nom: follow */
/* auteur: Jean-Paul Kneib */
/* date: 10/02/92 */
/* place: Toulouse */
/****************************************************************/
/* Follow the critical line using the trapeze algorithm. (see next function)
* Algorithm stop when the next position is close enough to the origin O.
*
* Return the radial array with the sequence of image and source points
* that are on the critical line.
* Parameters :
* - A and B are the initial direction of the critical line
* - O is the origin and final position on the critical line
*
* Global variables used :
* - CL, radial, nrline, flagr
* - in next() : G, lens
* - in e_dpl() : G, lens, lens_table
* */
void follow( struct point A,
struct point B,
struct point O,
double dl0s, double dos, double zs )
{
extern struct g_cline CL;
extern struct biline radial[NMAX];
extern int nrline, flagr;
struct point C;
register int i;
for ( i = 0; i < NRLINEMAX && nrline < 5*NRLINEMAX ; i++)
{
radial[nrline].i = flagr;
C = radial[nrline].I = next(A, B, CL.cpas, dl0s, dos, zs);
e_dpl(&C, dl0s / dos, &radial[nrline++].S);
if ( dist(O, C) > CL.cpas )
{
A = B;
B = C;
}
else
return;
};
}
/****************************************************************/
/* Return the next point of the critical line close to A and B.
* Algorithm looks for the critical line to cross any of the 4 sides
* of a trapeze which symetric axis is the (AB) segment.
* Parameters :
* - A and B define the trapeze region of search
* - dpl is the half size of the basis of the trapeze
*
* Global variables used :
* - in e_zeroamp() : G, lens
* - in ch_signe() : G, lens
* */
struct point next(struct point A, struct point B, double dpl,
double dl0s, double dos, double zs)
{
double norme, dx, dy;
struct point A1, A2, A3, A4;
struct point col, perp;
dx = B.x - A.x;
dy = B.y - A.y;
norme = sqrt(dx*dx + dy*dy);
col.x = dx / norme;
col.y = dy / norme;
perp.x = -col.y;
perp.y = col.x;
A1.x = B.x + dpl*perp.x;
A1.y = B.y + dpl*perp.y;
A2.x = B.x + dpl*(col.x + perp.x / 2.);
A2.y = B.y + dpl*(col.y + perp.y / 2.);
A3.x = B.x + dpl*(col.x - perp.x / 2.);
A3.y = B.y + dpl*(col.y - perp.y / 2.);
A4.x = B.x - dpl*perp.x;
A4.y = B.y - dpl*perp.y;
if ( chsigne(A1, A2, dl0s, dos, zs) != 0 )
return( e_zeroamp(A1, A2, dl0s, dos, zs) );
else if ( chsigne(A2, A3, dl0s, dos, zs) != 0 )
return( e_zeroamp(A2, A3, dl0s, dos, zs) );
else if ( chsigne(A3, A4, dl0s, dos, zs) != 0 )
return( e_zeroamp(A3, A4, dl0s, dos, zs) );
else if ( dpl > .01 )
return( next(A, B, dpl / 2., dl0s, dos, zs) );
else
return(A);
}

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