|
public ComputeMass ( |
||
| massData | Returns the mass data for this shape. | |
| return | void | |
// TODO_ERIN adjust linear velocity and torque to account for movement of center.
/// <summary>
/// Compute the mass properties from the attached shapes. You typically call this
/// after adding all the shapes. If you add or remove shapes later, you may want
/// to call this again. Note that this changes the center of mass position.
/// </summary>
public void SetMassFromShapes()
{
Box2DXDebug.Assert(_world._lock == false);
if (_world._lock == true)
{
return;
}
// Compute mass data from shapes. Each shape has its own density.
_mass = 0.0f;
_invMass = 0.0f;
_I = 0.0f;
_invI = 0.0f;
Vector2 center = Vector2.zero;
for (Fixture f = _fixtureList; f != null; f = f.Next)
{
MassData massData;
f.ComputeMass(out massData);
_mass += massData.Mass;
center += massData.Mass * massData.Center;
_I += massData.I;
}
// Compute center of mass, and shift the origin to the COM.
if (_mass > 0.0f)
{
_invMass = 1.0f / _mass;
center *= _invMass;
}
if (_I > 0.0f && (_flags & BodyFlags.FixedRotation) == 0)
{
// Center the inertia about the center of mass.
_I -= _mass * Vector2.Dot(center, center);
Box2DXDebug.Assert(_I > 0.0f);
_invI = 1.0f / _I;
}
else
{
_I = 0.0f;
_invI = 0.0f;
}
// Move center of mass.
_sweep.LocalCenter = center;
_sweep.C0 = _sweep.C = _xf.TransformPoint(_sweep.LocalCenter);
BodyType oldType = _type;
if (_invMass == 0.0f && _invI == 0.0f)
{
_type = BodyType.Static;
}
else
{
_type = BodyType.Dynamic;
}
// If the body type changed, we need to refilter the broad-phase proxies.
if (oldType != _type)
{
for (Fixture f = _fixtureList; f != null; f = f.Next)
{
f.RefilterProxy(_world._broadPhase, _xf);
}
}
}