void
plStepParticleSystem(PLparticles *ps, float dt)
{
assert(ps != NULL);
if (ps->enabled == false) return;
size_t activeParticles = 0;
for (size_t i = 0 ; i < ps->particleCount ; ++i) {
if (ps->particles[i].active) {
ps->particles[i].p += vf3_s_mul(ps->particles[i].v, dt) + vf3_s_mul(ps->obj->v, dt);
ps->particles[i].age += dt;
activeParticles++;
if (ps->particles[i].age > ps->particles[i].lifeTime) {
ps->particles[i].active = false;
int_array_push(&ps->freeParticles, i);
activeParticles --;
}
}
}
// Auto disable
if (ps->autoDisable) {
if (activeParticles == 0) {
ps->enabled = false;
}
return;
}
// Not off or disabled, emitt new particles
float newPartCount = ps->emissionRate * dt * (1.0 + rand_percent(10));
float intPart;
float frac = modff(newPartCount, &intPart);
unsigned newParticles = (unsigned) intPart;
// The fraction is handled with randomisation
int rval = random() % 128;
if ((float)rval/128.0f < frac) newParticles ++;
for (unsigned i = 0 ; i < newParticles ; ++i) {
if (ps->freeParticles.length > 0) {
int i = int_array_remove(&ps->freeParticles, 0);
ps->particles[i].active = true;
ps->particles[i].age = 0.0;
// Adjust lifetime by +-20 %
ps->particles[i].lifeTime = ps->lifeTime + ps->lifeTime * rand_percent(20);
ps->particles[i].p = v_q_rot(ps->p, ps->obj->q);
ps->particles[i].v = v_q_rot(ps->v * vf3_set(rand_percent(10), rand_percent(10), rand_percent(10)), ps->obj->q);
ps->particles[i].rgb = ps->rgb;
} else {
break;
}
}
}
/*!
\param a Semi-major axis
\param b Semi-minor axis
\param ecc Eccentricity of orbit
\param GM Gravitational parameter of orbited object GM
\param t Absolute time in seconds.
*/
float3
plOrbitPosAtTime(pl_keplerelems_t *orbit, double GM, double t)
{
long double meanMotion = plMeanMotion(GM, orbit->a);
long double eccAnomaly = pl_ecc_anomaly(orbit->ecc, meanMotion, t);
/* Compute x, y from anomaly, y is pointing in the direction of the
periapsis */
double y = orbit->a * cos(eccAnomaly) - orbit->a * orbit->ecc; // NOTE: on the plane we usually do x = a cos t
double x = -orbit->b * sin(eccAnomaly); // Since we use y as primary axis, x points downwards
quaternion_t q = orbit->qOrbit;
float3 v = vf3_set(x, y, 0.0);
v = v_q_rot(v, q);
assert(isfinite(v.x));
assert(isfinite(v.y));
assert(isfinite(v.z));
return v;
}
