void electric_point_charge(struct Structure This_Structure, float grid_span, int grid_size, float *grid) {
/************/
/* Counters */
int residue, atom;
/* Co-ordinates */
int x, y, z;
int x_low, x_high, y_low, y_high, z_low, z_high;
float a, b, c;
float x_corner, y_corner, z_corner;
float w;
/* Variables */
float one_span;
/************/
for (x = 0; x < grid_size; x++) {
for (y = 0; y < grid_size; y++) {
for (z = 0; z < grid_size; z++) {
grid[gaddress(x, y, z, grid_size)] = (float)0;
}
}
}
/************/
one_span = grid_span / (float)grid_size;
for (residue = 1; residue <= This_Structure.length; residue++) {
for (atom = 1; atom <= This_Structure.Residue[residue].size; atom++) {
if (This_Structure.Residue[residue].Atom[atom].charge != 0) {
x_low = gord(This_Structure.Residue[residue].Atom[atom].coord[1] - (one_span / 2),
grid_span,
grid_size);
y_low = gord(This_Structure.Residue[residue].Atom[atom].coord[2] - (one_span / 2),
grid_span,
grid_size);
z_low = gord(This_Structure.Residue[residue].Atom[atom].coord[3] - (one_span / 2),
grid_span,
grid_size);
x_high = x_low + 1;
y_high = y_low + 1;
z_high = z_low + 1;
a = This_Structure.Residue[residue].Atom[atom].coord[1] -
gcentre(x_low, grid_span, grid_size) - (one_span / 2);
b = This_Structure.Residue[residue].Atom[atom].coord[2] -
gcentre(y_low, grid_span, grid_size) - (one_span / 2);
c = This_Structure.Residue[residue].Atom[atom].coord[3] -
gcentre(z_low, grid_span, grid_size) - (one_span / 2);
for (x = x_low; x <= x_high; x++) {
x_corner = one_span * ((float)(x - x_high) + .5);
for (y = y_low; y <= y_high; y++) {
y_corner = one_span * ((float)(y - y_high) + .5);
for (z = z_low; z <= z_high; z++) {
z_corner = one_span * ((float)(z - z_high) + .5);
w = ((x_corner + a) * (y_corner + b) * (z_corner + c)) /
(8.0 * x_corner * y_corner * z_corner);
grid[gaddress(x, y, z,
grid_size)] +=
(float)(w * This_Structure.Residue[residue].Atom[atom].charge);
}
}
}
}
}
}
/************/
}
void discretise_structure( struct Structure This_Structure , float grid_span , int grid_size , float *grid ) {
/************/
/* Counters */
int residue , atom ;
/* Co-ordinates */
int x , y , z ;
int steps , x_step , y_step , z_step ;
float x_centre , y_centre , z_centre ;
/* Variables */
float distance , one_span ;
/************/
one_span = grid_span / (float)grid_size ;
distance = 1.8 ;
/************/
for( x = 0 ; x < grid_size ; x ++ ) {
for( y = 0 ; y < grid_size ; y ++ ) {
for( z = 0 ; z < grid_size ; z ++ ) {
grid[gaddress(x,y,z,grid_size)] = (float)0 ;
}
}
}
/************/
steps = (int)( ( distance / one_span ) + 1.5 ) ;
for( residue = 1 ; residue <= This_Structure.length ; residue ++ ) {
for( atom = 1 ; atom <= This_Structure.Residue[residue].size ; atom ++ ) {
x = gord( This_Structure.Residue[residue].Atom[atom].coord[1] , grid_span , grid_size ) ;
y = gord( This_Structure.Residue[residue].Atom[atom].coord[2] , grid_span , grid_size ) ;
z = gord( This_Structure.Residue[residue].Atom[atom].coord[3] , grid_span , grid_size ) ;
for( x_step = max( ( x - steps ) , 0 ) ; x_step <= min( ( x + steps ) , ( grid_size - 1 ) ) ; x_step ++ ) {
x_centre = gcentre( x_step , grid_span , grid_size ) ;
for( y_step = max( ( y - steps ) , 0 ) ; y_step <= min( ( y + steps ) , ( grid_size - 1 ) ) ; y_step ++ ) {
y_centre = gcentre( y_step , grid_span , grid_size ) ;
for( z_step = max( ( z - steps ) , 0 ) ; z_step <= min( ( z + steps ) , ( grid_size - 1 ) ) ; z_step ++ ) {
z_centre = gcentre( z_step , grid_span , grid_size ) ;
if( pythagoras( This_Structure.Residue[residue].Atom[atom].coord[1] , This_Structure.Residue[residue].Atom[atom].coord[2] , This_Structure.Residue[residue].Atom[atom].coord[3] , x_centre , y_centre , z_centre ) < distance ) grid[gaddress(x_step,y_step,z_step,grid_size)] = (float)1 ;
}
}
}
}
}
/************/
return ;
}
double *gauss2lats(int nlat, double *ylat) {
const double xlim = 1.0E-7;
double *cosc = (double *) malloc(sizeof(double) * (nlat + 1));
double *sinc = (double *) malloc(sizeof(double) * (nlat + 1));
double *colat = (double *) malloc(sizeof(double) * (nlat + 1));
int nzero = (nlat / 2);
int i;
double fi = nlat;
double fi1 = fi + 1.0;
double a = fi * fi1/sqrt(4.0*fi1*fi1 - 1.0);
double b = fi1 * fi/sqrt(4.0*fi*fi - 1.0);
double g, gm, gp, gt, delta, d;
for (i = 1; i <= nzero; i++) {
cosc[i] = sin((i - 0.5)*M_PI/nlat + M_PI*0.5);
}
for (i = 1; i <= nzero; i++) {
g = gord(nlat, cosc[i]);
gm = gord(nlat - 1, cosc[i]);
gp = gord(nlat + 1, cosc[i]);
gt = (cosc[i]*cosc[i] - 1.0)/(a * gp - b * gm);
delta = g*gt;
cosc[i] = cosc[i] - delta;
while ( fabs(delta) > xlim ) {
g = gord(nlat,cosc[i]);
gm = gord(nlat - 1, cosc[i]);
gp = gord(nlat + 1, cosc[i]);
gt = (cosc[i]*cosc[i] - 1.0)/(a * gp - b * gm);
delta = g*gt;
cosc[i] = cosc[i] - delta;
} /* end while */
} /* end for */
for (i = 1; i <= nzero; i++) {
colat[i] = acos(cosc[i]);
sinc[i] = sin(colat[i]);
}
/*
* ... deal with equator if odd number of points
*/
if ( ( nlat % 2) != 0 ) {
i = nzero + 1;
cosc[i] = 0.0;
d = gord(nlat - 1, cosc[i]);
d = d*d*fi*fi;
colat[i] = M_PI * 0.5;
sinc[i] = 1.0;
} /* end if() */
/*
* ... deal with southern hemisphere by symmetry
*/
for (i = nlat - nzero + 1; i <= nlat; i++) {
cosc[i] = -cosc[nlat + 1 - i];
colat[i] = M_PI - colat[nlat + 1 - i];
sinc[i] = sinc[nlat + 1 - i];
} /* end for(i) */
for (i = 1; i <= nlat; i++) {
ylat[i-1] = todegrees(acos(sinc[i]));
if ( i > (nlat / 2) ) ylat[i-1] = -ylat[i-1];
/* change from N-S to S-N */
ylat[i-1] = -ylat[i-1];
}
free(cosc);
free(sinc);
free(colat);
return ylat;
} /* end gauss2lats() */
