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/*****************************************************************
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m2d_int_seg_seg.c Type:Func
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Intersection entre segment AB et le sement MN
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Date de creation : Wed Feb 19 14:36:10 1997
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Derniere version : Thu May 8 10:09:04 1997
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Vincent FRANCOIS
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*****************************************************************/
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/**************************/
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/* include */
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#include <stdio.h>
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#include <math.h>
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#include <math.h>
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#include "const.h"
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#include "struct.h"
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#include "memoire.h"
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#include "prototype.h"
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/**************************/
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/* variables globales */
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extern struct environnement env;
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extern struct s_mesh *mesh;
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/**************************/
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/* programme principal */
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#define VRAI 1
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#define FAUX 0
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int m2d_int_seg_seg(int a,int b,int m,int n)
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{
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struct s_noeud *noa,*nob,*nom,*non;
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float ab[3],nm[3],am[3],an[3],det,sol1,sol2,tmp;
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float eps,eps2;
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float ua,va,ub,vb,un,vn,um,vm,du,dv;
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int equation[4],ne1,ne2;
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noa=ADRESSE(a,noeud,mesh->);
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nob=ADRESSE(b,noeud,mesh->);
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nom=ADRESSE(m,noeud,mesh->);
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non=ADRESSE(n,noeud,mesh->);
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/* decalage */
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if (mesh->rev_u!=0.) du=0.5*mesh->rev_u-noa->u; else du=0.;
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if (mesh->rev_v!=0.) dv=0.5*mesh->rev_v-noa->v; else dv=0.;
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eval_decale(&ua,du,noa->u,U);
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eval_decale(&va,dv,noa->v,V);
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eval_decale(&ub,du,nob->u,U);
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eval_decale(&vb,dv,nob->v,V);
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eval_decale(&un,du,non->u,U);
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eval_decale(&vn,dv,non->v,V);
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eval_decale(&um,du,nom->u,U);
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eval_decale(&vm,dv,nom->v,V);
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ab[0]=ub-ua;
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ab[1]=vb-va;
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ab[2]=0.;
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nm[0]=um-un;
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nm[1]=vm-vn;
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nm[2]=0.;
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am[0]=um-ua;
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am[1]=vm-va;
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am[2]=0.;
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equation[0]=1; /* etat de l'equation 0 */
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equation[1]=1;
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equation[2]=1;
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equation[3]=3; /* cette variable comporte le bilan du nombre d'equation */
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eps2=PSCA(ab,ab);
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eps=(float)sqrt((double)eps2);
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eps=eps*0.0001;
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eps2=eps2*0.0001;
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/* recherche du nombre d'equation -> inter franche ou para ou confondu */
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if ( (EGAL(ab[0],0,eps)) && (EGAL(nm[0],0,eps)) )
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if (EGAL(am[0],0,eps)) equation[0]=0; else return(FAUX);
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if ( (EGAL(ab[1],0,eps)) && (EGAL(nm[1],0,eps)) )
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if (EGAL(am[1],0,eps)) equation[1]=0; else return(FAUX);
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if ( (EGAL(ab[2],0,eps)) && (EGAL(nm[2],0,eps)) )
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if (EGAL(am[2],0,eps)) equation[2]=0; else return(FAUX);
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equation[3]=equation[0]+equation[1]+equation[2];
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if (equation[3]==3)
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{
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det=DETER(ab[0],nm[0],ab[1],nm[1]);
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if ((float)fabs((double)det)>eps2)
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{
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det=1/det;
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sol1=det*DETER(am[0],nm[0],am[1],nm[1]);
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sol2=det*DETER(ab[0],am[0],ab[1],am[1]);
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if ( (float)fabs((double)(sol1*ab[2]-sol2*nm[2]-am[2]))>eps2) return(FAUX);
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return(m2d_ex_sol(sol1,sol2,1));
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}
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else
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{
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equation[0]=0;
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equation[3]=2;
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/* on verifie la compatibilite des deux equations dont le det est nul*/
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if (ab[0]!=0) tmp=ab[1]*am[0]/ab[0]; else tmp=nm[1]*am[0]/nm[0];
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if (!(EGAL(tmp,am[1],eps))) return(FAUX);
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}
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}
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if (equation[3]==2)
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{
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/* on repere les equations qui existent */
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if (equation[0]!=0)
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{
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ne1=0;
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if (equation[1]!=0) ne2=1; else ne2=2;
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}
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else
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{
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ne1=1;
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ne2=2;
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}
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det=DETER(ab[ne1],nm[ne1],ab[ne2],nm[ne2]);
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if ((float)fabs((double)det)>eps2)
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{
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det=1/det;
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sol1=det*DETER(am[ne1],nm[ne1],am[ne2],nm[ne2]);
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sol2=det*DETER(ab[ne1],am[ne1],ab[ne2],am[ne2]);
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return(m2d_ex_sol(sol1,sol2,1));
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}
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else
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{
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equation[ne1]=0;
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equation[3]=1;
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/* on verifie la compatibilite des deux equations dont le det est nul */
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if (ab[ne1]!=0) tmp=ab[ne2]*am[ne1]/ab[ne1]; else tmp=nm[ne2]*am[ne1]/nm[ne1];
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if (!(EGAL(tmp,am[ne2],eps))) return(FAUX);
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}
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}
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if (equation[3]==1)
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{
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/* on repere l' equation qui existe */
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if (equation[0]!=0) ne1=0; else
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if (equation[1]!=0) ne1=1; else ne1=2;
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an[0]=un-ua;
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an[1]=vn-va;
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an[2]=0.;
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tmp=1/ab[ne1];
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sol1=am[ne1]*tmp;
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sol2=an[ne1]*tmp;
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return(m2d_ex_sol(sol1,sol2,2));
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}
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return(0);
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}
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