Project290.Physics.Dynamics.Body.ResetMassData C# (CSharp) Method

        public void ResetMassData()
        {
            // Compute mass data from shapes. Each shape has its own density.
            _mass = 0.0f;
            InvMass = 0.0f;
            _inertia = 0.0f;
            InvI = 0.0f;
            Sweep.LocalCenter = Vector2.Zero;

            // Kinematic bodies have zero mass.
            if (BodyType == BodyType.Kinematic)
            {
                Sweep.C0 = Sweep.C = Xf.Position;
                return;
            }

            Debug.Assert(BodyType == BodyType.Dynamic || BodyType == BodyType.Static);

            // Accumulate mass over all fixtures.
            Vector2 center = Vector2.Zero;
            foreach (Fixture f in FixtureList)
            {
                if (f.Shape._density == 0)
                {
                    continue;
                }

                MassData massData = f.Shape.MassData;
                _mass += massData.Mass;
                center += massData.Mass*massData.Centroid;
                _inertia += massData.Inertia;
            }

            //Static bodies only have mass, they don't have other properties. A little hacky tho...
            if (BodyType == BodyType.Static)
            {
                Sweep.C0 = Sweep.C = Xf.Position;
                return;
            }

            // Compute center of mass.
            if (_mass > 0.0f)
            {
                InvMass = 1.0f/_mass;
                center *= InvMass;
            }
            else
            {
                // Force all dynamic bodies to have a positive mass.
                _mass = 1.0f;
                InvMass = 1.0f;
            }

            if (_inertia > 0.0f && (Flags & BodyFlags.FixedRotation) == 0)
            {
                // Center the inertia about the center of mass.
                _inertia -= _mass*Vector2.Dot(center, center);

                Debug.Assert(_inertia > 0.0f);
                InvI = 1.0f/_inertia;
            }
            else
            {
                _inertia = 0.0f;
                InvI = 0.0f;
            }

            // Move center of mass.
            Vector2 oldCenter = Sweep.C;
            Sweep.LocalCenter = center;
            Sweep.C0 = Sweep.C = MathUtils.Multiply(ref Xf, ref Sweep.LocalCenter);

            // Update center of mass velocity.
            Vector2 a = Sweep.C - oldCenter;
            LinearVelocityInternal += new Vector2(-AngularVelocityInternal*a.Y, AngularVelocityInternal*a.X);
        }

        public Fixture(Body body, Shape shape, Object userData)
        {
            CollisionFilter = new CollisionFilter(this);

            //Fixture defaults
            Friction    = 0.2f;
            Restitution = 0;

            IsSensor = false;

            Body     = body;
            UserData = userData;

            if (Settings.ConserveMemory)
            {
                Shape = shape;
            }
            else
            {
                Shape = shape.Clone();
            }

            // Reserve proxy space
            int childCount = Shape.ChildCount;

            Proxies = new FixtureProxy[childCount];
            for (int i = 0; i < childCount; ++i)
            {
                Proxies[i]         = new FixtureProxy();
                Proxies[i].Fixture = null;
                Proxies[i].ProxyId = BroadPhase.NullProxy;
            }
            ProxyCount = 0;

            FixtureId = _fixtureIdCounter++;

            if ((Body.Flags & BodyFlags.Enabled) == BodyFlags.Enabled)
            {
                BroadPhase broadPhase = Body.World.ContactManager.BroadPhase;
                CreateProxies(broadPhase, ref Body.Xf);
            }

            Body.FixtureList.Add(this);

            // Adjust mass properties if needed.
            if (Shape._density > 0.0f)
            {
                Body.ResetMassData();
            }

            // Let the world know we have a new fixture. This will cause new contacts
            // to be created at the beginning of the next time step.
            Body.World.Flags |= WorldFlags.NewFixture;

            if (Body.World.FixtureAdded != null)
            {
                Body.World.FixtureAdded(this);
            }
        }