void SPHSystem::computeForce()
{
int i, j, s, numNei;
float dij;
float term1, term2;
Point3f vij;
Point3f pf, vf, tf, gf, cf;
//#pragma omp parallel for private( j, nId, numNei, d, term1, term2, dv, pf, vf, tf, gf )
for(i=0; i<p.size(); ++i) {
pf.Set(0,0,0);
vf.Set(0,0,0);
tf.Set(0,0,0);
numNei = p[i]->pq.getSize();
for(s=1; s<=numNei; ++s) {
j = p[i]->pq.queue[s];
if(i==j) continue;
term1 = p[i]->p/(p[i]->d*p[i]->d);
term2 = p[j]->p/(p[j]->d*p[j]->d);
vij = *p[i]-*p[j];
dij = vij.Length();
// pressure force
pf += (term1+term2)*p[j]->m*k->pw1(dij)*vij;
// viscosity force
vf += p[j]->m*k->vw2(dij)*(p[j]->v-p[i]->v);
// surface tension
}
pf = -p[i]->d*pf;
vf = (X/p[i]->d)*vf;
gf = p[i]->d*Point3f(0.0f, -GR, 0.0f);
if(p[i]->n.Length() < ( SIM_DIM==2 ? 0.6f : 3.0f) ) // for 2d < 0.6 , 3d < 3.0
tf.Zero();
else
tf = -p[i]->lapc*p[i]->n.GetNormalized();
p[i]->tf = tf;
p[i]->pf = pf;
p[i]->vf = vf;
p[i]->a = (pf+vf+gf+tf)/p[i]->d;
}
}
void SPHSystem::computeDensityPressure()
{
int i, j, s, numNei;
float lapc, c, d;
float w;
float vj; // volumn
float lenij; // length (i,j)
Point3f n;
Point3f vecij; // vector (i,j)
for(i=0; i<p.size(); ++i) {
p[i]->vol = p[i]->m/p[i]->d;
}
#pragma omp parallel for private(s, j, numNei, lapc, c, d, w, vj, lenij, n, vecij )
for(i=0; i<p.size(); ++i) {
lapc = 0;
c = 0;
d = 0;
n.Zero();
numNei = p[i]->pq.getSize();
for(s=1; s<=numNei; ++s) {
j = p[i]->pq.queue[s];
vj = p[j]->vol;
vecij = *p[i]-*p[j];
lenij = vecij.Length();
w = k->w(lenij);
c += p[j]->c*p[j]->m*(vj)*w;
n += p[j]->m*(vj)*k->w1(lenij)*(vecij);
lapc += p[j]->m*(vj)*k->w2(lenij);
d += p[j]->m*w;
}
p[i]->lapc = lapc; // laplacian of c
p[i]->c = c; // color field
p[i]->n = n; // inward surface normal
p[i]->d = d; // density
p[i]->p = (K*RHO/7.0f)*(pow((d/RHO),7.0f)-1); // pressure (Tait Equation, http://graphics.stanford.edu/~wicke/eg09-tutorial/coursenotes.pdf)
if(p[i]->p < 0) // correct pressure if p<0
p[i]->p *= Z; // reduce it to a tiny number (~=0)
}
}