/// <summary>
/// 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.
/// </summary>
/// <param name="massData">the mass properties.</param>
public void SetMassData(MassData massData)
{
// TODO_ERIN adjust linear velocity and torque to account for movement of center.
Debug.Assert(World.Locked == false);
if (World.Locked)
{
return;
}
if (m_type != BodyType.Dynamic)
{
return;
}
InvMass = 0.0f;
I = 0.0f;
InvI = 0.0f;
Mass = massData.Mass;
if (Mass <= 0.0f)
{
Mass = 1f;
}
InvMass = 1.0f / Mass;
if (massData.I > 0.0f && (Flags & TypeFlags.FixedRotation) == 0)
{
I = massData.I - Mass * Vec2.Dot(massData.Center, massData.Center);
Debug.Assert(I > 0.0f);
InvI = 1.0f / I;
}
Vec2 oldCenter = World.Pool.PopVec2();
// Move center of mass.
oldCenter.Set(Sweep.C);
Sweep.LocalCenter.Set(massData.Center);
// m_sweep.c0 = m_sweep.c = Mul(m_xf, m_sweep.localCenter);
Transform.MulToOutUnsafe(Xf, Sweep.LocalCenter, Sweep.C0);
Sweep.C.Set(Sweep.C0);
// Update center of mass velocity.
// m_linearVelocity += Cross(m_angularVelocity, m_sweep.c - oldCenter);
Vec2 temp = World.Pool.PopVec2();
temp.Set(Sweep.C).SubLocal(oldCenter);
Vec2.CrossToOut(m_angularVelocity, temp, temp);
m_linearVelocity.AddLocal(temp);
World.Pool.PushVec2(2);
}
/// <summary>
/// Set this as a single edge.
/// </summary>
/// <param name="v1"></param>
/// <param name="v2"></param>
/// <deprecated></deprecated>
public void SetAsEdge(Vec2 v1, Vec2 v2)
{
VertexCount = 2;
Vertices[0].Set(v1);
Vertices[1].Set(v2);
Centroid.Set(v1).AddLocal(v2).MulLocal(0.5f);
// = 0.5f * (v1 + v2);
Normals[0].Set(v2).SubLocal(v1);
Vec2.CrossToOut(Normals[0], 1f, Normals[0]);
// m_normals[0] = Cross(v2 - v1, 1.0f);
Normals[0].Normalize();
Normals[1].Set(Normals[0]).NegateLocal();
}
public void GetLinearVelocityFromWorldPointToOut(Vec2 worldPoint, Vec2 result)
{
result.Set(worldPoint).SubLocal(Sweep.C);
Vec2.CrossToOut(m_angularVelocity, result, result);
result.AddLocal(m_linearVelocity);
}