BulletSim: add check in avatar stair step code to verify the collision

is not with a volume detect object.

This fixes a problem of avatars trying to step over a volume detect object
that they collide with. This appeared as the avatar popping up as it started
to step up but then continuing on since the object wasn't physically interacting.

OpenSim/Region/Physics/BulletSPlugin/BSActorAvatarMove.cs

@@ -310,6 +310,11 @@ public class BSActorAvatarMove : BSActor
             {
                 // Don't care about collisions with the terrain
                 if (kvp.Key > m_physicsScene.TerrainManager.HighestTerrainID)
+                {
+                    BSPhysObject collisionObject;
+                    if (m_physicsScene.PhysObjects.TryGetValue(kvp.Key, out collisionObject))
+                    {
+                        if (!collisionObject.IsVolumeDetect)
                         {
                             OMV.Vector3 touchPosition = kvp.Value.Position;
                             m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs,min={1},max={2},touch={3}",
@@ -330,6 +335,8 @@ public class BSActorAvatarMove : BSActor
                             }
                         }
                     }
+                }
+            }
             m_walkingUpStairs = 0;
             // If there is a good step sensing, move the avatar over the step.
             if (highestTouchPosition != OMV.Vector3.Zero)

OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs

@@ -404,6 +404,7 @@ public sealed class BSCharacter : BSPhysObject
 
     // Allows the detection of collisions with inherently non-physical prims. see llVolumeDetect for more
     public override void SetVolumeDetect(int param) { return; }
+    public override bool IsVolumeDetect { get { return false; } }
 
     public override OMV.Vector3 GeometricCenter { get { return OMV.Vector3.Zero; } }
     public override OMV.Vector3 CenterOfMass { get { return OMV.Vector3.Zero; } }

OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs

@@ -175,6 +175,7 @@ public abstract class BSPhysObject : PhysicsActor
     public abstract bool IsSolid { get; }
     public abstract bool IsStatic { get; }
     public abstract bool IsSelected { get; }
+    public abstract bool IsVolumeDetect { get; }
 
     // Materialness
     public MaterialAttributes.Material Material { get; private set; }

OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs

@@ -617,6 +617,10 @@ public class BSPrim : BSPhysObject
         }
         return;
     }
+    public override bool IsVolumeDetect
+    {
+        get { return _isVolumeDetect; }
+    }
     public override void SetMaterial(int material)
     {
         base.SetMaterial(material);