void OpenCloth::computeForces( float deltaTime ) {
for( int i = 0; i < _totalPoints; ++i ) {
_forces[i].x = _forces[i].y = _forces[i].z = 0.0f;
const cc::Vec3f velocity = getVerletVelocity(_positions[i], _lastPositions[i], deltaTime);
if( (i != 0) && (i != _divsX) ) {
_forces[i] += _gravity * _mass;
}
_forces[i] += _damping * velocity;
}
for( int i = 0; i < _springCount; ++i ) {
const cc::Vec3f& p1 = _positions[_springs[i].p1];
const cc::Vec3f& p1Last = _lastPositions[_springs[i].p1];
const cc::Vec3f& p2 = _positions[_springs[i].p2];
const cc::Vec3f& p2Last = _lastPositions[_springs[i].p2];
const cc::Vec3f v1 = getVerletVelocity(p1, p1Last, deltaTime);
const cc::Vec3f v2 = getVerletVelocity(p2, p2Last, deltaTime);
const cc::Vec3f deltaP = p1 - p2;
const cc::Vec3f deltaV = v1 - v2;
const float dist = deltaP.magnitude();
const float leftTerm = -_springs[i].ks * (dist - _springs[i].restLength);
const float rightTerm = _springs[i].kd * (deltaV.dot(deltaP) / dist);
const cc::Vec3f springForce = (leftTerm + rightTerm) * deltaP.normalized();
if( _springs[i].p1 != 0 && _springs[i].p1 != _divsX ) {
_forces[_springs[i].p1] += springForce;
}
if( _springs[i].p2 != 0 && _springs[i].p2 != _divsX ) {
_forces[_springs[i].p2] -= springForce;
}
}
}
static void setVec3Length( cc::Vec3f& vec, float newLength ) {
const float length = vec.magnitude();
if( length != 0.0f ) {
const float factor = newLength / length;
vec.x *= factor;
vec.y *= factor;
vec.z *= factor;
}
}