void ComputeForces()
{
for(int i = 0; i < numCells; ++i) {
Cell *cell = &cells[i];
int np = cnumPars[i];
for(int j = 0; j < np; ++j) {
cell->density[j % PARTICLES_PER_CELL] = 0.0;
cell->a[j % PARTICLES_PER_CELL] = externalAcceleration;
//move pointer to next cell in list if end of array is reached
if(j % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
cell = cell->next;
}
}
}
int neighCells[3*3*3];
int cindex = 0;
for(int ck = 0; ck < nz; ++ck) {
for(int cj = 0; cj < ny; ++cj) {
for(int ci = 0; ci < nx; ++ci, ++cindex) {
int np = cnumPars[cindex];
if(np == 0)
continue;
int numNeighCells = GetNeighborCells(ci, cj, ck, neighCells);
Cell *cell = &cells[cindex];
for(int ipar = 0; ipar < np; ++ipar) {
for(int inc = 0; inc < numNeighCells; ++inc) {
int cindexNeigh = neighCells[inc];
Cell *neigh = &cells[cindexNeigh];
int numNeighPars = cnumPars[cindexNeigh];
for(int iparNeigh = 0; iparNeigh < numNeighPars; ++iparNeigh) {
//Check address to make sure densities are computed only once per pair
if(&neigh->p[iparNeigh % PARTICLES_PER_CELL] < &cell->p[ipar % PARTICLES_PER_CELL])
{
fptype distSq = (cell->p[ipar % PARTICLES_PER_CELL] - neigh->p[iparNeigh % PARTICLES_PER_CELL]).GetLengthSq();
if(distSq < hSq)
{
fptype t = hSq - distSq;
fptype tc = t*t*t;
cell->density[ipar % PARTICLES_PER_CELL] += tc;
neigh->density[iparNeigh % PARTICLES_PER_CELL] += tc;
}
}
//move pointer to next cell in list if end of array is reached
if(iparNeigh % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
neigh = neigh->next;
}
}
}
//move pointer to next cell in list if end of array is reached
if(ipar % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
cell = cell->next;
}
}
}
}
}
const fptype tc = hSq*hSq*hSq;
for(int i = 0; i < numCells; ++i) {
Cell *cell = &cells[i];
int np = cnumPars[i];
for(int j = 0; j < np; ++j) {
cell->density[j % PARTICLES_PER_CELL] += tc;
cell->density[j % PARTICLES_PER_CELL] *= densityCoeff;
//move pointer to next cell in list if end of array is reached
if(j % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
cell = cell->next;
}
}
}
cindex = 0;
for(int ck = 0; ck < nz; ++ck) {
for(int cj = 0; cj < ny; ++cj) {
for(int ci = 0; ci < nx; ++ci, ++cindex) {
int np = cnumPars[cindex];
if(np == 0)
continue;
int numNeighCells = GetNeighborCells(ci, cj, ck, neighCells);
Cell *cell = &cells[cindex];
for(int ipar = 0; ipar < np; ++ipar) {
for(int inc = 0; inc < numNeighCells; ++inc) {
int cindexNeigh = neighCells[inc];
Cell *neigh = &cells[cindexNeigh];
int numNeighPars = cnumPars[cindexNeigh];
for(int iparNeigh = 0; iparNeigh < numNeighPars; ++iparNeigh) {
//Check address to make sure forces are computed only once per pair
if(&neigh->p[iparNeigh % PARTICLES_PER_CELL] < &cell->p[ipar % PARTICLES_PER_CELL])
{
Vec3 disp = cell->p[ipar % PARTICLES_PER_CELL] - neigh->p[iparNeigh % PARTICLES_PER_CELL];
fptype distSq = disp.GetLengthSq();
if(distSq < hSq)
{
#ifndef ENABLE_DOUBLE_PRECISION
fptype dist = sqrtf(std::max(distSq, (fptype)1e-12));
#else
fptype dist = sqrt(std::max(distSq, 1e-12));
#endif //ENABLE_DOUBLE_PRECISION
fptype hmr = h - dist;
Vec3 acc = disp * pressureCoeff * (hmr*hmr/dist) * (cell->density[ipar % PARTICLES_PER_CELL]+neigh->density[iparNeigh % PARTICLES_PER_CELL] - doubleRestDensity);
acc += (neigh->v[iparNeigh % PARTICLES_PER_CELL] - cell->v[ipar % PARTICLES_PER_CELL]) * viscosityCoeff * hmr;
acc /= cell->density[ipar % PARTICLES_PER_CELL] * neigh->density[iparNeigh % PARTICLES_PER_CELL];
cell->a[ipar % PARTICLES_PER_CELL] += acc;
neigh->a[iparNeigh % PARTICLES_PER_CELL] -= acc;
}
}
//move pointer to next cell in list if end of array is reached
if(iparNeigh % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
neigh = neigh->next;
}
}
}
//move pointer to next cell in list if end of array is reached
if(ipar % PARTICLES_PER_CELL == PARTICLES_PER_CELL-1) {
cell = cell->next;
}
}
}
}
}
}
