/** 开始拖动刚体*/
private void startDragBody(b2Body b, float x, float y)
{
if (b == null || b.GetType() != b2Body.b2_dynamicBody)
{
return;
}
if (_mj != null)
{
_world.DestroyJoint(_mj);
}
b2MouseJointDef jointDef = new b2MouseJointDef();
jointDef.bodyA = _world.GetGroundBody();
jointDef.bodyB = b;
jointDef.target.Set(x, y);
jointDef.maxForce = 1e6f;
_mj = _world.CreateJoint(jointDef) as b2MouseJoint;
}
// friend class b2Joint;
// p = attached point, m = mouse point
// C = p - m
// Cdot = v
// = v + cross(w, r)
// J = [I r_skew]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
internal b2MouseJoint(b2MouseJointDef def) : base(def)
{
Debug.Assert(def.target.IsValid());
Debug.Assert(Utils.b2IsValid(def.maxForce) && def.maxForce >= 0.0f);
Debug.Assert(Utils.b2IsValid(def.frequencyHz) && def.frequencyHz >= 0.0f);
Debug.Assert(Utils.b2IsValid(def.dampingRatio) && def.dampingRatio >= 0.0f);
m_targetA = def.target;
m_localAnchorB = Utils.b2MulT(m_bodyB.GetTransform(), m_targetA);
m_maxForce = def.maxForce;
m_impulse.SetZero();
m_frequencyHz = def.frequencyHz;
m_dampingRatio = def.dampingRatio;
m_beta = 0.0f;
m_gamma = 0.0f;
}
public virtual bool MouseDown(b2Vec2 p)
{
m_mouseWorld = p;
if (m_mouseJoint != null)
{
return(false);
}
// Make a small box.
b2AABB aabb = new b2AABB();
b2Vec2 d = new b2Vec2();
d.Set(0.001f, 0.001f);
aabb.LowerBound = p - d;
aabb.UpperBound = p + d;
// Query the world for overlapping shapes.
QueryCallback callback = new QueryCallback(p);
m_world.QueryAABB(callback, aabb);
if (callback.m_fixture != null)
{
b2Body body = callback.m_fixture.Body;
b2MouseJointDef md = new b2MouseJointDef();
md.BodyA = m_groundBody;
md.BodyB = body;
md.target = p;
md.maxForce = 1000.0f * body.Mass;
m_mouseJoint = (b2MouseJoint)m_world.CreateJoint(md);
body.SetAwake(true);
return(true);
}
return(false);
}
internal static global::System.Runtime.InteropServices.HandleRef getCPtr(b2MouseJointDef obj)
{
return((obj == null) ? new global::System.Runtime.InteropServices.HandleRef(null, global::System.IntPtr.Zero) : obj.swigCPtr);
}