Fix a bug I introduced yesterday in ODE physics where prim scripts would only receive the very first collision.

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -2082,6 +2082,8 @@ namespace OpenSim.Region.Framework.Scenes
 
         public void PhysicsCollision(EventArgs e)
         {
+//            m_log.DebugFormat("Invoking PhysicsCollision on {0} {1} {2}", Name, LocalId, UUID);
+
             // single threaded here
 
             CollisionEventUpdate a = (CollisionEventUpdate)e;

OpenSim/Region/Physics/Manager/PhysicsActor.cs

@@ -76,6 +76,8 @@ namespace OpenSim.Region.Physics.Manager
         /// </summary>
         public int Count { get { return m_objCollisionList.Count; } }
 
+        public bool CollisionsOnPreviousFrame { get; private set; }
+
         public Dictionary<uint, ContactPoint> m_objCollisionList;
 
         public CollisionEventUpdate(Dictionary<uint, ContactPoint> objCollisionList)

OpenSim/Region/Physics/OdePlugin/ODEPrim.cs

@@ -193,6 +193,15 @@ namespace OpenSim.Region.Physics.OdePlugin
         private int m_eventsubscription;
         private CollisionEventUpdate CollisionEventsThisFrame = new CollisionEventUpdate();
 
+        /// <summary>
+        /// Signal whether there were collisions on the previous frame, so we know if we need to send the
+        /// empty CollisionEventsThisFrame to the prim so that it can detect the end of a collision.
+        /// </summary>
+        /// <remarks>
+        /// This is probably a temporary measure, pending storing this information consistently in CollisionEventUpdate itself.
+        /// </remarks>
+        private bool m_collisionsOnPreviousFrame;
+
         private IntPtr m_linkJoint = IntPtr.Zero;
 
         internal volatile bool childPrim;
@@ -3025,8 +3034,20 @@ Console.WriteLine(" JointCreateFixed");
 
         public void SendCollisions()
         {
-            if (CollisionEventsThisFrame.Count > 0)
+            if (m_collisionsOnPreviousFrame || CollisionEventsThisFrame.Count > 0)
+            {
                 base.SendCollisionUpdate(CollisionEventsThisFrame);
+
+                if (CollisionEventsThisFrame.Count > 0)
+                {
+                    m_collisionsOnPreviousFrame = true;
+                    CollisionEventsThisFrame.Clear();
+                }
+                else
+                {
+                    m_collisionsOnPreviousFrame = false;
+                }
+            }
         }
 
         public override bool SubscribedEvents()