#config clearmemory	//general initialization
#config complexoff
#config gl		//3D-graphics initialisation
#config axesoff
#config labelsoff
#config rasteroff


A[0]=3.34;     //position first electric charge
A[1]=3;
A[2]=3;
A[3]=6;        //value

B[0]=-3;       //position of second electric charge
B[1]=-3;
B[2]=-3;
B[3]=-6;       //value
L=0;
M=0;
N="0";

glstartlist;		//display list for the charge ball
glbegin(polygon);
glpoint(-1,0,0);
glpoint(-0.707,0.707,0);
glpoint(0,1,0);
glpoint(0.707,0.707,0);
glpoint(1,0,0);
glpoint(0.707,-0.707,0);
glpoint(0,-1,0);
glpoint(-0.707,-0.707,0);
glend;
glbegin(polygon);
glpoint(-1,0,0);
glpoint(-0.707,0,0.707);
glpoint(0,0,1);
glpoint(0.707,0,0.707);
glpoint(1,0,0);
glpoint(0.707,0,-0.707);
glpoint(0,0,-1);
glpoint(-0.707,0,-0.707);
glend;
glbegin(polygon);
glpoint(0,-1,0);
glpoint(0,-0.707,0.707);
glpoint(0,0,1);
glpoint(0,0.707,0.707);
glpoint(0,1,0);
glpoint(0,0.707,-0.707);
glpoint(0,0,-1);
glpoint(0,-0.707,-0.707);
glend;
P=glendlist;


while(1)
{
glclear;		//clear scene
glbegin(lines);		//calculate field
for(C[0]=-9; C[0]<11; C[0]=C[0]+3)
{
  for(C[1]=-9; C[1]<11; C[1]=C[1]+3)
  {
    for(C[2]=-10; C[2]<11; C[2]=C[2]+2)
    {
       D[0]=A[0];
       D[1]=A[1];
       D[2]=A[2];
       E[0]=C[0];
       E[1]=C[1];
       E[2]=C[2];
       F=E[]-D[];
       G=sqrt(F[0]^2+F[1]^2+F[2]^2);
       F=F[]*A[3];

       D[0]=B[0];
       D[1]=B[1];
       D[2]=B[2];
       H=E[]-D[];
       K=sqrt(H[0]^2+H[1]^2+H[2]^2);
       H=H[]*B[3];

       E[0]=A[0];
       E[1]=A[1];
       E[2]=A[2];
       J=(1/G^2)*F[]+(1/K^2)*H[];
       I=sqrt(J[0]^2+J[1]^2+J[2]^2);
       J=J[]*(3/I);
       glcolor(I*100,0,255-I*100);
       glpoint(C[0]-J[0]/2,C[1]-J[1]/2,C[2]-J[2]/2);
       glpoint(C[0]+J[0]/2,C[1]+J[1]/2,C[2]+J[2]/2);
    
    }
  }
}
glend;
glstring(10,20,"Charge1");	//draw information text
glstring(100,20,A[0]);
glstring(150,20,A[1]);
glstring(200,20,A[2]);
glstring(250,20,A[3]);
if(L<4)
  glstring(100+L*50,20,"__");
glstring(10,35,"Charge2");
glstring(100,35,B[0]);
glstring(150,35,B[1]);
glstring(200,35,B[2]);
glstring(250,35,B[3]);
if(L>=4)
  glstring(100+(L-4)*50,35,"__");
glstring(10,50,N);
glloadidentity;
if(A[3]>0)			//draw charge balls
  glcolor(255,0,0);
else glcolor(0,0,255);
glmove(A[0],A[1],A[2]);
glscale(0.5,0.5,0.5);
glcalllist(P);
glrotate(45,1,1,1);
glcalllist(P);
glloadidentity;
if(B[3]>0)
  glcolor(255,0,0);
else glcolor(0,0,255);
glmove(B[0],B[1],B[2]);
glscale(0.5,0.5,0.5);
glcalllist(P);
glrotate(45,1,1,1);
glcalllist(P);
glshow;
O=getkey;			//recive keyboard input
N[M]=O[0];
if(N[M]==13)			//process keyboard input
{
  N[M]=0;
  
  if(M>0)
  {
    if(L<4)
      A[L]=(float)N;
    else B[L-4]=(float)N;
  }
  L=L+1;
  if(L>7)
    L=0;
  M=0;
  N="0";
}
else M=M+1;

}