static Plane constructFromPointNormal( const cc::Vec3f& point, const cc::Vec3f& normal ) {
Plane result;
const cc::Vec3f normalizedNormal = normal.normalized();
result.normal = normalizedNormal;
result.constant = -point.dot(normalizedNormal);
return result;
}
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;
}
}
}
void OpenCloth::addSpring( int* idx, int a, int b, float ks, float kd ) {
_springs[*idx].p1 = a;
_springs[*idx].p2 = b;
_springs[*idx].ks = ks;
_springs[*idx].kd = kd;
const cc::Vec3f deltaP = _positions[a] - _positions[b];
_springs[*idx].restLength = sqrtf(deltaP.dot(deltaP));
*idx += 1;
}
