/** Compute forces and update particles **/
void ParticleSystem::computeForcesAndUpdateParticles(float t)
{
time = t;
if (!simulate) return;
for (int i = 0; i < 20; i++)
{
for (int j = 19; j >= 0; j--)
{
if (i == 0 && (j == 0 || j == 19)) continue;
Vec3f force = Vec3f(g);
Vec3f position = particles[i][j].getPosition();
force += springForce(i - 1, j, position);
force += springForce(i + 1, j, position);
force += springForce(i, j - 1, position);
force += springForce(i, j + 1, position);
if (force.length() > 10)
{
force.normalize();
force *= 10;
}
particles[i][j].applyForce(force);
}
}
for (int i = 0; i < 20; i++)
for (int j = 19; j >= 0; j--)
particles[i][j].move(t);
bakeParticles(t);
}
/** Compute forces and update initial_state **/
void ParticleSystem::computeForcesAndUpdateParticles(float t)
{
// TODO
if (simulate){
// no need to update if the particles are already baked
float roundedTime = round(t*bake_fps) / bake_fps;
if (bakedParticles.count(roundedTime)){
return;
}
// compute new force
for (int i = 0; i < n; i++){
// clear force accumulator
float newForVectors[3] = { 0.0, 0.0, 0.0 };
particles[i].setPositionVectors(newForVectors);
float* derivatives = new float[6 * n];
float totalForce[3] = { 0.0, 0.0, 0.0 };
// gravity force
float gravityForce[3] = { 0.0, particles[i].getMass() * (-1) * 9.8, 0.0 };
totalForce[0] += gravityForce[0];
totalForce[1] += gravityForce[1];
totalForce[2] += gravityForce[2];
// air drag
float airDragCoeff = 10;
float airDrag[3] = { airDragCoeff*particles[i].getVelocityVectors()[0], airDragCoeff*particles[i].getVelocityVectors()[1], airDragCoeff*particles[i].getVelocityVectors()[2] };
totalForce[0] += airDrag[0];
totalForce[1] += airDrag[1];
totalForce[2] += airDrag[2];
//update particles derivatives
derivatives[0] = particles[i].getVelocityVectors()[0];
derivatives[1] = particles[i].getVelocityVectors()[1];
derivatives[2] = particles[i].getVelocityVectors()[2];
derivatives[3] = totalForce[0] / particles[i].getMass();
derivatives[4] = totalForce[1] / particles[i].getMass();
derivatives[5] = totalForce[2] / particles[i].getMass();
float newPosVectors[3];
float newVelVectors[3];
newPosVectors[0] = particles[i].getPositionVectors()[0] + 1.0 / bake_fps*derivatives[0];
newPosVectors[1] = particles[i].getPositionVectors()[1] + 1.0 / bake_fps*derivatives[1];
newPosVectors[2] = particles[i].getPositionVectors()[2] + 1.0 / bake_fps*derivatives[2];
newVelVectors[0] = particles[i].getVelocityVectors()[0] + 1.0 / bake_fps*derivatives[3];
newVelVectors[1] = particles[i].getVelocityVectors()[1] + 1.0 / bake_fps*derivatives[4];
newVelVectors[2] = particles[i].getVelocityVectors()[2] + 1.0 / bake_fps*derivatives[5];
// reset the position of the particles if it exceeds the limit
double limit = 5.0;
if (newPosVectors[0] > limit || newPosVectors[1] > limit || newPosVectors[2] > limit){
newPosVectors[0] = initial_state[i].getPositionVectors()[0];
newPosVectors[1] = initial_state[i].getPositionVectors()[1];
newPosVectors[2] = initial_state[i].getPositionVectors()[2];
newVelVectors[0] = initial_state[i].getVelocityVectors()[0];
newVelVectors[1] = initial_state[i].getVelocityVectors()[1];
newVelVectors[2] = initial_state[i].getVelocityVectors()[2];
}
// update particles state
particles[i].setPositionVectors(newPosVectors);
particles[i].setVelocityVectors(newVelVectors);
particles[i].setForceVectors(totalForce);
delete[] derivatives;
}
bakeParticles(roundedTime);
}
}