/**
* Set the mass properties to override the mass properties of the fixtures. Note that this changes
* the center of mass position. Note that creating or destroying fixtures can also alter the mass.
* This function has no effect if the body isn't dynamic.
*
* @param massData the mass properties.
*/
public final void setMassData(MassData massData) {
// TODO_ERIN adjust linear velocity and torque to account for movement of center.
assert (m_world.isLocked() == false);
if (m_world.isLocked() == true) {
return;
}
if (m_type != BodyType.DYNAMIC) {
return;
}
m_invMass = 0.0f;
m_I = 0.0f;
m_invI = 0.0f;
m_mass = massData.mass;
if (m_mass <= 0.0f) {
m_mass = 1f;
}
m_invMass = 1.0f / m_mass;
if (massData.I > 0.0f && (m_flags & e_fixedRotationFlag) == 0) {
m_I = massData.I - m_mass * Vec2.dot(massData.center, massData.center);
assert (m_I > 0.0f);
m_invI = 1.0f / m_I;
}
final Vec2 oldCenter = m_world.getPool().popVec2();
// Move center of mass.
oldCenter.set(m_sweep.c);
m_sweep.localCenter.set(massData.center);
// m_sweep.c0 = m_sweep.c = Mul(m_xf, m_sweep.localCenter);
Transform.mulToOut(m_xf, m_sweep.localCenter, m_sweep.c0);
m_sweep.c.set(m_sweep.c0);
// Update center of mass velocity.
// m_linearVelocity += Cross(m_angularVelocity, m_sweep.c - oldCenter);
final Vec2 temp = m_world.getPool().popVec2();
temp.set(m_sweep.c).subLocal(oldCenter);
Vec2.crossToOut(m_angularVelocity, temp, temp);
m_linearVelocity.addLocal(temp);
m_world.getPool().pushVec2(2);
}
/**
* This resets the mass properties to the sum of the mass properties of the fixtures. This
* normally does not need to be called unless you called setMassData to override the mass and you
* later want to reset the mass.
*/
public final void resetMassData() {
// Compute mass data from shapes. Each shape has its own density.
m_mass = 0.0f;
m_invMass = 0.0f;
m_I = 0.0f;
m_invI = 0.0f;
m_sweep.localCenter.setZero();
// Static and kinematic bodies have zero mass.
if (m_type == BodyType.STATIC || m_type == BodyType.KINEMATIC) {
// m_sweep.c0 = m_sweep.c = m_xf.position;
m_sweep.c.set(m_xf.position);
m_sweep.c0.set(m_xf.position);
return;
}
assert (m_type == BodyType.DYNAMIC);
// Accumulate mass over all fixtures.
final Vec2 center = m_world.getPool().popVec2();
center.setZero();
final Vec2 temp = m_world.getPool().popVec2();
final MassData massData = pmd;
for (Fixture f = m_fixtureList; f != null; f = f.m_next) {
if (f.m_density == 0.0f) {
continue;
}
f.getMassData(massData);
m_mass += massData.mass;
// center += massData.mass * massData.center;
temp.set(massData.center).mulLocal(massData.mass);
center.addLocal(temp);
m_I += massData.I;
}
// Compute center of mass.
if (m_mass > 0.0f) {
m_invMass = 1.0f / m_mass;
center.mulLocal(m_invMass);
} else {
// Force all dynamic bodies to have a positive mass.
m_mass = 1.0f;
m_invMass = 1.0f;
}
if (m_I > 0.0f && (m_flags & e_fixedRotationFlag) == 0) {
// Center the inertia about the center of mass.
m_I -= m_mass * Vec2.dot(center, center);
assert (m_I > 0.0f);
m_invI = 1.0f / m_I;
} else {
m_I = 0.0f;
m_invI = 0.0f;
}
Vec2 oldCenter = m_world.getPool().popVec2();
// Move center of mass.
oldCenter.set(m_sweep.c);
m_sweep.localCenter.set(center);
// m_sweep.c0 = m_sweep.c = Mul(m_xf, m_sweep.localCenter);
Transform.mulToOut(m_xf, m_sweep.localCenter, m_sweep.c0);
m_sweep.c.set(m_sweep.c0);
// Update center of mass velocity.
// m_linearVelocity += Cross(m_angularVelocity, m_sweep.c - oldCenter);
temp.set(m_sweep.c).subLocal(oldCenter);
Vec2.crossToOut(m_angularVelocity, temp, temp);
m_linearVelocity.addLocal(temp);
m_world.getPool().pushVec2(3);
}