bulletworld.cs

            new Thread(() => {
                using(CollisionConfiguration collisionConf = new DefaultCollisionConfiguration())
                using(Dispatcher dispatcher = new CollisionDispatcher(collisionConf))
                using(BroadphaseInterface broadphase = new DbvtBroadphase())
                using(DynamicsWorld physicsWorld = new DiscreteDynamicsWorld(dispatcher, broadphase, null, collisionConf)) {
                    physicsWorld.Gravity = new Vector3(0, -1, 0);

                    for (int i = 0; i < _renderableBodies.Length; i++) {
                        var renderableBody = _renderableBodies[i];

                        const float mass = 1.0f;
                        //Add a single cube
                        var shape = new BoxShape(1f, 1f, 1f);
                        Vector3 localInertia = Vector3.Zero;
                        shape.CalculateLocalInertia(mass, out localInertia);
                        var rbInfo = new RigidBodyConstructionInfo(mass, renderableBody.MotionState, shape, localInertia);
                        var body = new RigidBody(rbInfo);
                        rbInfo.Dispose();

                        var position = renderableBody.InitialPosition.ToBullet();
                        var rotation = renderableBody.InitialRotation.ToBullet();
                
                        Matrix st = Matrix.Translation(position);
                        st = Matrix.Add(st, Matrix.RotationQuaternion(rotation));
                        body.WorldTransform = st;
                        physicsWorld.AddRigidBody(body);
                    }

                    isPhysicsEngineStarted.Set();

                    float fixedTimePassed = 0;
                    var physicsCancelledToken = _cancelPhysicsToken.Token;
                    while (!physicsCancelledToken.IsCancellationRequested) {
                        float currentTime = _stopwatch.ElapsedMilliseconds / 1000f;
                        float fixedDeltaTime = currentTime - fixedTimePassed;

                        int totalStepsPerformed = physicsWorld.StepSimulation(fixedDeltaTime, 5, _physicsTimeStep);
                        fixedTimePassed += _physicsTimeStep * totalStepsPerformed;

                        if (totalStepsPerformed > 0) {
                            _motionStateGroup.PrepareRender();
                        }

                        //Debug.Log("physics tick at " + (deltaTime));
                        int sleepIntervalInMs = ((int) (_physicsTimeStep * 1000)) / 4;
                        Thread.Sleep(sleepIntervalInMs);
                    }
                }
                UnityEngine.Debug.Log("Physics engine destroyed");
            }).Start();