BulletSim: add runtime setting of physics parameters. Update default values.

4 files changed, 256 insertions, 28 deletions

diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs b/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
index 9f9ebcc..682eb80 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSCharacter.cs
@@ -49,8 +49,9 @@ public class BSCharacter : PhysicsActor
     private bool _grabbed;
     private bool _selected;
     private Vector3 _position;
-    private float _mass = 80f;
-    public float _density = 60f;
+    private float _mass;
+    public float _density;
+    public float _avatarVolume;
     private Vector3 _force;
     private Vector3 _velocity;
     private Vector3 _torque;
@@ -90,13 +91,13 @@ public class BSCharacter : PhysicsActor
         _scene = parent_scene;
         _position = pos;
         _size = size;
+        _flying = isFlying;
         _orientation = Quaternion.Identity;
         _velocity = Vector3.Zero;
-        _buoyancy = 0f; // characters return a buoyancy of zero
+        _buoyancy = isFlying ? 1f : 0f;
         _scale = new Vector3(1f, 1f, 1f);
-        float AVvolume = (float) (Math.PI*Math.Pow(_scene.Params.avatarCapsuleRadius, 2)*_scene.Params.avatarCapsuleHeight);
         _density = _scene.Params.avatarDensity;
-        _mass = _density*AVvolume;
+        ComputeAvatarVolumeAndMass();   // set _avatarVolume and _mass based on capsule size, _density and _scale
 
         ShapeData shapeData = new ShapeData();
         shapeData.ID = _localID;
@@ -106,7 +107,7 @@ public class BSCharacter : PhysicsActor
         shapeData.Velocity = _velocity;
         shapeData.Scale = _scale;
         shapeData.Mass = _mass;
-        shapeData.Buoyancy = isFlying ? 1f : 0f;
+        shapeData.Buoyancy = _buoyancy;
         shapeData.Static = ShapeData.numericFalse;
         shapeData.Friction = _scene.Params.avatarFriction;
         shapeData.Restitution = _scene.Params.defaultRestitution;
@@ -212,6 +213,7 @@ public class BSCharacter : PhysicsActor
         get { return _velocity; } 
         set {
             _velocity = value;
+            // m_log.DebugFormat("{0}: set velocity = {1}", LogHeader, _velocity);
             _scene.TaintedObject(delegate()
             {
                 BulletSimAPI.SetObjectVelocity(_scene.WorldID, _localID, _velocity);
@@ -235,6 +237,7 @@ public class BSCharacter : PhysicsActor
         get { return _orientation; } 
         set {
             _orientation = value;
+            // m_log.DebugFormat("{0}: set orientation to {1}", LogHeader, _orientation);
             _scene.TaintedObject(delegate()
             {
                 // _position = BulletSimAPI.GetObjectPosition(_scene.WorldID, _localID);
@@ -300,7 +303,6 @@ public class BSCharacter : PhysicsActor
         set { _buoyancy = value; 
             _scene.TaintedObject(delegate()
             {
-                // simulate flying by changing the effect of gravity
                 BulletSimAPI.SetObjectBuoyancy(_scene.WorldID, LocalID, _buoyancy);
             });
         } 
@@ -344,6 +346,7 @@ public class BSCharacter : PhysicsActor
             _force.X += force.X;
             _force.Y += force.Y;
             _force.Z += force.Z;
+            // m_log.DebugFormat("{0}: AddForce. adding={1}, newForce={2}", LogHeader, force, _force);
             _scene.TaintedObject(delegate()
             {
                 BulletSimAPI.SetObjectForce(_scene.WorldID, _localID, _force);
@@ -370,6 +373,17 @@ public class BSCharacter : PhysicsActor
         return (_subscribedEventsMs > 0);
     }
 
+    // set _avatarVolume and _mass based on capsule size, _density and _scale
+    private void ComputeAvatarVolumeAndMass()
+    {
+        _avatarVolume = (float)(
+                        Math.PI
+                        * _scene.Params.avatarCapsuleRadius * _scale.X
+                        * _scene.Params.avatarCapsuleRadius * _scale.Y
+                        * _scene.Params.avatarCapsuleHeight * _scale.Z);
+        _mass = _density * _avatarVolume;
+    }
+
     // The physics engine says that properties have updated. Update same and inform
     // the world that things have changed.
     public void UpdateProperties(EntityProperties entprop)
@@ -403,6 +417,9 @@ public class BSCharacter : PhysicsActor
         }
         if (changed)
         {
+            // m_log.DebugFormat("{0}: UpdateProperties: id={1}, c={2}, pos={3}, rot={4}", LogHeader, LocalID, changed, _position, _orientation);
+            // Avatar movement is not done by generating this event. There is a system that
+            //  checks for avatar updates each heartbeat loop.
             // base.RequestPhysicsterseUpdate();
         }
     }
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs b/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
index c4999f6..cc414e9 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSPrim.cs
@@ -1013,8 +1013,8 @@ public sealed class BSPrim : PhysicsActor
             // m_log.DebugFormat("{0}: CreateGeom: calling CreateHull. lid={1}, key={2}, hulls={3}", LogHeader, _localID, _hullKey, hullCount);
             BulletSimAPI.CreateHull(_scene.WorldID, _hullKey, hullCount, convHulls);
             _shapeType = ShapeData.PhysicsShapeType.SHAPE_HULL;
-            // Let the object be scaled by Bullet (the mesh was created as a unit mesh)
-            _scale = _size;
+            // meshes are already scaled by the meshmerizer
+            _scale = new OMV.Vector3(1f, 1f, 1f);
         }
         return;
     }
@@ -1138,9 +1138,7 @@ public sealed class BSPrim : PhysicsActor
         if (_scene.NeedsMeshing(_pbs))  // linksets with constraints don't need a root mesh
         {
             // m_log.DebugFormat("{0}: RecreateGeomAndObject: creating mesh", LogHeader);
-            // Make the mesh scaled to 1 and use Bullet's scaling feature to scale it in world
-            OMV.Vector3 scaleFactor = new OMV.Vector3(1.0f, 1.0f, 1.0f);
-            _mesh = _scene.mesher.CreateMesh(_avName, _pbs, scaleFactor, _scene.MeshLOD, _isPhysical);
+            _mesh = _scene.mesher.CreateMesh(_avName, _pbs, _size, _scene.MeshLOD, _isPhysical);
         }
         else
         {
@@ -1225,6 +1223,8 @@ public sealed class BSPrim : PhysicsActor
         else
         {
             // Don't check for damping here -- it's done in BulletSim and SceneObjectPart.
+
+            // Only updates only for individual prims and for the root object of a linkset.
             if (this._parentPrim == null)
             {
                 // Assign to the local variables so the normal set action does not happen
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs b/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
index de86d59..518be09 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
@@ -58,11 +58,13 @@ using OpenSim.Region.Framework;
 // 
 namespace OpenSim.Region.Physics.BulletSPlugin
 {
-public class BSScene : PhysicsScene
+public class BSScene : PhysicsScene, IPhysicsParameters
 {
     private static readonly ILog m_log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
     private static readonly string LogHeader = "[BULLETS SCENE]";
 
+    public string BulletSimVersion = "?";
+
     private Dictionary<uint, BSCharacter> m_avatars = new Dictionary<uint, BSCharacter>();
     private Dictionary<uint, BSPrim> m_prims = new Dictionary<uint, BSPrim>();
     private List<BSPrim> m_vehicles = new List<BSPrim>();
@@ -127,7 +129,7 @@ public class BSScene : PhysicsScene
     ConfigurationParameters[] m_params;
     GCHandle m_paramsHandle;
 
-    private BulletSimAPI.DebugLogCallback debugLogCallbackHandle;
+    private BulletSimAPI.DebugLogCallback m_DebugLogCallbackHandle;
 
     public BSScene(string identifier)
     {
@@ -149,12 +151,17 @@ public class BSScene : PhysicsScene
         m_updateArray = new EntityProperties[m_maxUpdatesPerFrame];
         m_updateArrayPinnedHandle = GCHandle.Alloc(m_updateArray, GCHandleType.Pinned);
 
+        // Get the version of the DLL
+        // TODO: this doesn't work yet. Something wrong with marshaling the returned string.
+        // BulletSimVersion = BulletSimAPI.GetVersion();
+        // m_log.WarnFormat("{0}: BulletSim.dll version='{1}'", LogHeader, BulletSimVersion);
+
         // if Debug, enable logging from the unmanaged code
         if (m_log.IsDebugEnabled)
         {
             m_log.DebugFormat("{0}: Initialize: Setting debug callback for unmanaged code", LogHeader);
-            debugLogCallbackHandle = new BulletSimAPI.DebugLogCallback(BulletLogger);
-            BulletSimAPI.SetDebugLogCallback(debugLogCallbackHandle);
+            m_DebugLogCallbackHandle = new BulletSimAPI.DebugLogCallback(BulletLogger);
+            BulletSimAPI.SetDebugLogCallback(m_DebugLogCallbackHandle);
         }
 
         _taintedObjects = new List<TaintCallback>();
@@ -188,7 +195,7 @@ public class BSScene : PhysicsScene
         m_maxUpdatesPerFrame = 2048;
         m_maximumObjectMass = 10000.01f;
 
-        parms.defaultFriction = 0.70f;
+        parms.defaultFriction = 0.5f;
         parms.defaultDensity = 10.000006836f; // Aluminum g/cm3
         parms.defaultRestitution = 0f;
         parms.collisionMargin = 0.0f;
@@ -202,10 +209,10 @@ public class BSScene : PhysicsScene
         parms.ccdMotionThreshold = 0.5f;    // set to zero to disable
         parms.ccdSweptSphereRadius = 0.2f;
 
-        parms.terrainFriction = 0.85f;
-        parms.terrainHitFriction = 0.8f;
-        parms.terrainRestitution = 0.2f;
-        parms.avatarFriction = 0.85f;
+        parms.terrainFriction = 0.5f;
+        parms.terrainHitFraction = 0.8f;
+        parms.terrainRestitution = 0f;
+        parms.avatarFriction = 0.0f;
         parms.avatarDensity = 60f;
         parms.avatarCapsuleRadius = 0.37f;
         parms.avatarCapsuleHeight = 1.5f; // 2.140599f
@@ -213,7 +220,8 @@ public class BSScene : PhysicsScene
         if (config != null)
         {
             // If there are specifications in the ini file, use those values
-            // WHEN ADDING OR UPDATING THIS SECTION, BE SURE TO ALSO UPDATE OpenSimDefaults.ini
+            // WHEN ADDING OR UPDATING THIS SECTION, BE SURE TO UPDATE OpenSimDefaults.ini
+            // ALSO REMEMBER TO UPDATE THE RUNTIME SETTING OF THE PARAMETERS.
             IConfig pConfig = config.Configs["BulletSim"];
             if (pConfig != null)
             {
@@ -243,7 +251,7 @@ public class BSScene : PhysicsScene
                 parms.ccdSweptSphereRadius = pConfig.GetFloat("CcdSweptSphereRadius", parms.ccdSweptSphereRadius);
 
                 parms.terrainFriction = pConfig.GetFloat("TerrainFriction", parms.terrainFriction);
-                parms.terrainHitFriction = pConfig.GetFloat("TerrainHitFriction", parms.terrainHitFriction);
+                parms.terrainHitFraction = pConfig.GetFloat("TerrainHitFraction", parms.terrainHitFraction);
                 parms.terrainRestitution = pConfig.GetFloat("TerrainRestitution", parms.terrainRestitution);
                 parms.avatarFriction = pConfig.GetFloat("AvatarFriction", parms.avatarFriction);
                 parms.avatarDensity = pConfig.GetFloat("AvatarDensity", parms.avatarDensity);
@@ -386,7 +394,7 @@ public class BSScene : PhysicsScene
             }
         }
 
-        // FIX THIS: fps calculation wrong. This calculation always returns about 1 in normal operation.
+        // TODO: FIX THIS: fps calculation wrong. This calculation always returns about 1 in normal operation.
         return timeStep / (numSubSteps * m_fixedTimeStep) * 1000f;
     }
 
@@ -651,5 +659,196 @@ public class BSScene : PhysicsScene
         }
     }
     #endregion Vehicles
+
+    #region Runtime settable parameters
+    public static PhysParameterEntry[] SettableParameters = new PhysParameterEntry[]
+    {
+        new PhysParameterEntry("MeshLOD", "Level of detail to render meshes (Power of two. Default 32)"),
+        new PhysParameterEntry("MaxSubStep", "In simulation step, maximum number of substeps"),
+        new PhysParameterEntry("FixedTimeStep", "In simulation step, seconds of one substep (1/60)"),
+        new PhysParameterEntry("MaxObjectMass", "Maximum object mass (10000.01)"),
+
+        new PhysParameterEntry("DefaultFriction", "Friction factor used on new objects"),
+        new PhysParameterEntry("DefaultDensity", "Density for new objects" ),
+        new PhysParameterEntry("DefaultRestitution", "Bouncyness of an object" ),
+        // new PhysParameterEntry("CollisionMargin", "Margin around objects before collisions are calculated (must be zero!!)" ),
+        new PhysParameterEntry("Gravity", "Vertical force of gravity (negative means down)" ),
+
+        new PhysParameterEntry("LinearDamping", "Factor to damp linear movement per second (0.0 - 1.0)" ),
+        new PhysParameterEntry("AngularDamping", "Factor to damp angular movement per second (0.0 - 1.0)" ),
+        new PhysParameterEntry("DeactivationTime", "Seconds before considering an object potentially static" ),
+        new PhysParameterEntry("LinearSleepingThreshold", "Seconds to measure linear movement before considering static" ),
+        new PhysParameterEntry("AngularSleepingThreshold", "Seconds to measure angular movement before considering static" ),
+        // new PhysParameterEntry("CcdMotionThreshold", "" ),
+        // new PhysParameterEntry("CcdSweptSphereRadius", "" ),
+
+        new PhysParameterEntry("TerrainFriction", "Factor to reduce movement against terrain surface" ),
+        new PhysParameterEntry("TerrainHitFraction", "Distance to measure hit collisions" ),
+        new PhysParameterEntry("TerrainRestitution", "Bouncyness" ),
+        new PhysParameterEntry("AvatarFriction", "Factor to reduce movement against an avatar. Changed on avatar recreation." ),
+        new PhysParameterEntry("AvatarDensity", "Density of an avatar. Changed on avatar recreation." ),
+        new PhysParameterEntry("AvatarRestitution", "Bouncyness. Changed on avatar recreation." ),
+        new PhysParameterEntry("AvatarCapsuleRadius", "Radius of space around an avatar" ),
+        new PhysParameterEntry("AvatarCapsuleHeight", "Default height of space around avatar" )
+    };
+
+    #region IPhysicsParameters
+    // Get the list of parameters this physics engine supports
+    public PhysParameterEntry[] GetParameterList()
+    {
+        return SettableParameters;
+    }
+
+    // Set parameter on a specific or all instances.
+    // Return 'false' if not able to set the parameter.
+    // Setting the value in the m_params block will change the value the physics engine
+    //   will use the next time since it's pinned and shared memory.
+    // Some of the values require calling into the physics engine to get the new
+    //   value activated ('terrainFriction' for instance).
+    public bool SetPhysicsParameter(string parm, float val, uint localID)
+    {
+        bool ret = true;
+        string lparm = parm.ToLower();
+        switch (lparm)
+        {
+            case "meshlod": m_meshLOD = (int)val; break;
+            case "maxsubstep": m_maxSubSteps = (int)val; break;
+            case "fixedtimestep": m_fixedTimeStep = val; break;
+            case "maxobjectmass": m_maximumObjectMass = val; break;
+
+            case "defaultfriction": m_params[0].defaultFriction = val; break;
+            case "defaultdensity": m_params[0].defaultDensity = val; break;
+            case "defaultrestitution": m_params[0].defaultRestitution = val; break;
+            case "collisionmargin": m_params[0].collisionMargin = val; break;
+            case "gravity": m_params[0].gravity = val;  TaintedUpdateParameter(lparm, PhysParameterEntry.APPLY_TO_NONE, val); break;
+
+            case "lineardamping": UpdateParameterPrims(ref m_params[0].linearDamping, lparm, localID, val); break;
+            case "angulardamping": UpdateParameterPrims(ref m_params[0].angularDamping, lparm, localID, val); break;
+            case "deactivationtime": UpdateParameterPrims(ref m_params[0].deactivationTime, lparm, localID, val); break;
+            case "linearsleepingthreshold": UpdateParameterPrims(ref m_params[0].linearSleepingThreshold, lparm, localID, val); break;
+            case "angularsleepingthreshold": UpdateParameterPrims(ref m_params[0].angularDamping, lparm, localID, val); break;
+            case "ccdmotionthreshold": UpdateParameterPrims(ref m_params[0].ccdMotionThreshold, lparm, localID, val); break;
+            case "ccdsweptsphereradius": UpdateParameterPrims(ref m_params[0].ccdSweptSphereRadius, lparm, localID, val); break;
+
+            // set a terrain physical feature and cause terrain to be recalculated
+            case "terrainfriction": m_params[0].terrainFriction = val; TaintedUpdateParameter("terrain", 0, val); break;
+            case "terrainhitfraction": m_params[0].terrainHitFraction = val; TaintedUpdateParameter("terrain", 0, val); break;
+            case "terrainrestitution": m_params[0].terrainRestitution = val; TaintedUpdateParameter("terrain", 0, val); break;
+            // set an avatar physical feature and cause avatar(s) to be recalculated
+            case "avatarfriction": UpdateParameterAvatars(ref m_params[0].avatarFriction, "avatar", localID, val); break;
+            case "avatardensity": UpdateParameterAvatars(ref m_params[0].avatarDensity, "avatar", localID, val);  break;
+            case "avatarrestitution": UpdateParameterAvatars(ref m_params[0].avatarRestitution, "avatar", localID, val); break;
+            case "avatarcapsuleradius": UpdateParameterAvatars(ref m_params[0].avatarCapsuleRadius, "avatar", localID, val);  break;
+            case "avatarcapsuleheight": UpdateParameterAvatars(ref m_params[0].avatarCapsuleHeight, "avatar", localID, val);  break;
+
+            default: ret = false; break;
+        }
+        return ret;
+    }
+
+    // check to see if we are updating a parameter for a particular or all of the prims
+    private void UpdateParameterPrims(ref float loc, string parm, uint localID, float val)
+    {
+        List<uint> operateOn;
+        lock (m_prims) operateOn = new List<uint>(m_prims.Keys);
+        UpdateParameterSet(operateOn, ref loc, parm, localID, val);
+    }
+
+    // check to see if we are updating a parameter for a particular or all of the avatars
+    private void UpdateParameterAvatars(ref float loc, string parm, uint localID, float val)
+    {
+        List<uint> operateOn;
+        lock (m_avatars) operateOn = new List<uint>(m_avatars.Keys);
+        UpdateParameterSet(operateOn, ref loc, parm, localID, val);
+    }
+
+    // update all the localIDs specified
+    // If the local ID is APPLY_TO_NONE, just change the default value
+    // If the localID is APPLY_TO_ALL change the default value and apply the new value to all the lIDs
+    // If the localID is a specific object, apply the parameter change to only that object
+    private void UpdateParameterSet(List<uint> lIDs, ref float defaultLoc, string parm, uint localID, float val)
+    {
+        switch (localID)
+        {
+            case PhysParameterEntry.APPLY_TO_NONE:
+                defaultLoc = val;   // setting only the default value
+                break;
+            case PhysParameterEntry.APPLY_TO_ALL:
+                defaultLoc = val;  // setting ALL also sets the default value
+                List<uint> objectIDs = lIDs;
+                string xparm = parm.ToLower();
+                float xval = val;
+                TaintedObject(delegate() {
+                    foreach (uint lID in objectIDs)
+                    {
+                        BulletSimAPI.UpdateParameter(m_worldID, lID, xparm, xval);
+                    }
+                });
+                break;
+            default: 
+                // setting only one localID
+                TaintedUpdateParameter(parm, localID, val);
+                break;
+        }
+    }
+
+    // schedule the actual updating of the paramter to when the phys engine is not busy
+    private void TaintedUpdateParameter(string parm, uint localID, float val)
+    {
+        uint xlocalID = localID;
+        string xparm = parm.ToLower();
+        float xval = val;
+        TaintedObject(delegate() {
+            BulletSimAPI.UpdateParameter(m_worldID, xlocalID, xparm, xval);
+        });
+    }
+
+    // Get parameter.
+    // Return 'false' if not able to get the parameter.
+    public bool GetPhysicsParameter(string parm, out float value)
+    {
+        float val = 0f;
+        bool ret = true;
+        switch (parm.ToLower())
+        {
+            case "meshlod": val = (float)m_meshLOD; break;
+            case "maxsubstep": val = (float)m_maxSubSteps; break;
+            case "fixedtimestep": val = m_fixedTimeStep; break;
+            case "maxobjectmass": val = m_maximumObjectMass; break;
+
+            case "defaultfriction": val = m_params[0].defaultFriction; break;
+            case "defaultdensity": val = m_params[0].defaultDensity; break;
+            case "defaultrestitution": val = m_params[0].defaultRestitution; break;
+            case "collisionmargin": val = m_params[0].collisionMargin; break;
+            case "gravity": val = m_params[0].gravity; break;
+
+            case "lineardamping": val = m_params[0].linearDamping; break;
+            case "angulardamping": val = m_params[0].angularDamping; break;
+            case "deactivationtime": val = m_params[0].deactivationTime; break;
+            case "linearsleepingthreshold": val = m_params[0].linearSleepingThreshold; break;
+            case "angularsleepingthreshold": val = m_params[0].angularDamping; break;
+            case "ccdmotionthreshold": val = m_params[0].ccdMotionThreshold; break;
+            case "ccdsweptsphereradius": val = m_params[0].ccdSweptSphereRadius; break;
+
+            case "terrainfriction": val = m_params[0].terrainFriction; break;
+            case "terrainhitfraction": val = m_params[0].terrainHitFraction; break;
+            case "terrainrestitution": val = m_params[0].terrainRestitution; break;
+
+            case "avatarfriction": val = m_params[0].avatarFriction; break;
+            case "avatardensity": val = m_params[0].avatarDensity; break;
+            case "avatarrestitution": val = m_params[0].avatarRestitution; break;
+            case "avatarcapsuleradius": val = m_params[0].avatarCapsuleRadius; break;
+            case "avatarcapsuleheight": val = m_params[0].avatarCapsuleHeight; break;
+            default: ret = false; break;
+
+        }
+        value = val;
+        return ret;
+    }
+
+    #endregion IPhysicsParameters
+
+    #endregion Runtime settable parameters
+
 }
 }
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs b/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
index 819fce1..bf953df 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BulletSimAPI.cs
@@ -51,9 +51,6 @@ public struct ShapeData
                 SHAPE_SPHERE = 4,
                 SHAPE_HULL = 5
     };
-    // note that bools are passed as ints since bool size changes by language
-    public const int numericTrue = 1;
-    public const int numericFalse = 0;
     public uint ID;
     public PhysicsShapeType Type;
     public Vector3 Position;
@@ -67,6 +64,10 @@ public struct ShapeData
     public float Restitution;
     public int Collidable;
     public int Static;  // true if a static object. Otherwise gravity, etc.
+
+    // note that bools are passed as ints since bool size changes by language and architecture
+    public const int numericTrue = 1;
+    public const int numericFalse = 0;
 }
 [StructLayout(LayoutKind.Sequential)]
 public struct SweepHit 
@@ -121,23 +122,34 @@ public struct ConfigurationParameters
         public float ccdSweptSphereRadius;
 
     public float terrainFriction;
-    public float terrainHitFriction;
+    public float terrainHitFraction;
     public float terrainRestitution;
     public float avatarFriction;
     public float avatarDensity;
     public float avatarRestitution;
     public float avatarCapsuleRadius;
     public float avatarCapsuleHeight;
+
+    public const float numericTrue = 1f;
+    public const float numericFalse = 0f;
 }
 
 static class BulletSimAPI {
 
 [DllImport("BulletSim", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
+[return: MarshalAs(UnmanagedType.LPStr)]
+public static extern string GetVersion();
+
+[DllImport("BulletSim", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
 public static extern uint Initialize(Vector3 maxPosition, IntPtr parms, 
                         int maxCollisions, IntPtr collisionArray, 
                         int maxUpdates, IntPtr updateArray);
 
 [DllImport("BulletSim", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
+public static extern bool UpdateParameter(uint worldID, uint localID,
+                        [MarshalAs(UnmanagedType.LPStr)]string paramCode, float value);
+
+[DllImport("BulletSim", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]
 public static extern void SetHeightmap(uint worldID, [MarshalAs(UnmanagedType.LPArray)] float[] heightMap);
 
 [DllImport("BulletSim", CallingConvention = CallingConvention.Cdecl), SuppressUnmanagedCodeSecurity]