Improve movement inertia

Handles all 3 axis. Incoming velocity is only added to inertia when
leaving the ground, and does not continually add to it.

apps/openmw/mwworld/physicssystem.cpp

@@ -132,8 +132,10 @@ namespace MWWorld
             position.z += halfExtents.z;
 
             OEngine::Physic::ActorTracer tracer;
-            bool onground = false;
+            bool wasOnGround = false;
+            bool isOnGround = false;
             const Ogre::Quaternion orient; // Don't rotate actor collision boxes
+            Ogre::Vector3 inertia(0.0f);
             Ogre::Vector3 velocity;
             if(!gravity)
             {
@@ -144,17 +146,19 @@ namespace MWWorld
             }
             else
             {
-                if(!(movement.z > 0.0f))
+                tracer.doTrace(colobj, position, position-Ogre::Vector3(0,0,4), engine);
+                if(tracer.mFraction < 1.0f && getSlope(tracer.mPlaneNormal) <= sMaxSlope)
                 {
-                    tracer.doTrace(colobj, position, position-Ogre::Vector3(0,0,4), engine);
-                    if(tracer.mFraction < 1.0f && getSlope(tracer.mPlaneNormal) <= sMaxSlope)
-                        onground = true;
+                    wasOnGround = true;
+                    if(!(movement.z > 0.0f))
+                        isOnGround = true;
                 }
-                velocity = Ogre::Quaternion(Ogre::Radian(-refpos.rot[2]), Ogre::Vector3::UNIT_Z) * movement;
-                velocity.z += physicActor->getVerticalForce();
+                inertia = physicActor->getInertialForce();
+                velocity  = Ogre::Quaternion(Ogre::Radian(-refpos.rot[2]), Ogre::Vector3::UNIT_Z) * movement;
+                velocity += inertia;
             }
 
-            if(onground)
+            if(isOnGround)
             {
                 // if we're on the ground, don't try to fall
                 velocity.z = std::max(0.0f, velocity.z);
@@ -179,7 +183,7 @@ namespace MWWorld
                 //std::cout<<"angle: "<<getSlope(trace.planenormal)<<"\n";
                 // We hit something. Try to step up onto it.
                 if(stepMove(colobj, newPosition, velocity, remainingTime, engine))
-                    onground = gravity;
+                    isOnGround = gravity;
                 else
                 {
                     // Can't move this way, try to find another spot along the plane
@@ -195,17 +199,25 @@ namespace MWWorld
                 }
             }
 
-            if(onground)
+            if(isOnGround)
             {
                 tracer.doTrace(colobj, newPosition, newPosition-Ogre::Vector3(0,0,sStepSize+4.0f), engine);
                 if(tracer.mFraction < 1.0f && getSlope(tracer.mPlaneNormal) <= sMaxSlope)
                     newPosition.z = tracer.mEndPos.z + 2.0f;
                 else
-                    onground = false;
+                    isOnGround = false;
             }
 
-            physicActor->setOnGround(onground);
-            physicActor->setVerticalForce(!onground ? velocity.z - time*627.2f : 0.0f);
+            physicActor->setOnGround(isOnGround);
+            if(isOnGround)
+                physicActor->setInertialForce(Ogre::Vector3(0.0f));
+            else
+            {
+                if(wasOnGround)
+                    inertia = velocity;
+                inertia.z -= time*627.2f;
+                physicActor->setInertialForce(inertia);
+            }
 
             newPosition.z -= halfExtents.z;
             return newPosition;

libs/openengine/bullet/physic.cpp

@@ -19,7 +19,8 @@ namespace Physic
 
     PhysicActor::PhysicActor(const std::string &name, const std::string &mesh, PhysicEngine *engine, const Ogre::Vector3 &position, const Ogre::Quaternion &rotation, float scale)
       : mName(name), mEngine(engine), mMesh(mesh), mBoxScaledTranslation(0,0,0), mBoxRotationInverse(0,0,0,0)
-      , mBody(0), mRaycastingBody(0), onGround(false), collisionMode(true), mBoxRotation(0,0,0,0), verticalForce(0.0f)
+      , mBody(0), mRaycastingBody(0), mOnGround(false), mCollisionMode(true), mBoxRotation(0,0,0,0)
+      , mForce(0.0f)
     {
         mBody = mEngine->createAndAdjustRigidBody(mMesh, mName, scale, position, rotation, &mBoxScaledTranslation, &mBoxRotation);
         mRaycastingBody = mEngine->createAndAdjustRigidBody(mMesh, mName, scale, position, rotation, &mBoxScaledTranslation, &mBoxRotation, true);
@@ -45,9 +46,9 @@ namespace Physic
     void PhysicActor::enableCollisions(bool collision)
     {
         assert(mBody);
-        if(collision && !collisionMode) enableCollisionBody();
-        if(!collision && collisionMode) disableCollisionBody();
-        collisionMode = collision;
+        if(collision && !mCollisionMode) enableCollisionBody();
+        if(!collision && mCollisionMode) disableCollisionBody();
+        mCollisionMode = collision;
     }
 
 
@@ -123,24 +124,14 @@ namespace Physic
         return Ogre::Vector3(0.0f);
     }
 
-    void PhysicActor::setVerticalForce(float force)
+    void PhysicActor::setInertialForce(const Ogre::Vector3 &force)
     {
-        verticalForce = force;
-    }
-
-    float PhysicActor::getVerticalForce() const
-    {
-        return verticalForce;
+        mForce = force;
     }
 
     void PhysicActor::setOnGround(bool grounded)
     {
-        onGround = grounded;
-    }
-
-    bool PhysicActor::getOnGround() const
-    {
-        return collisionMode && onGround;
+        mOnGround = grounded;
     }
 
     void PhysicActor::disableCollisionBody()

libs/openengine/bullet/physic.hpp

@@ -104,7 +104,7 @@ namespace Physic
 
         bool getCollisionMode() const
         {
-            return collisionMode;
+            return mCollisionMode;
         }
 
 
@@ -130,18 +130,24 @@ namespace Physic
         Ogre::Vector3 getHalfExtents() const;
 
         /**
-         * Sets the current amount of vertical force (gravity) affecting this physic actor
+         * Sets the current amount of inertial force (incl. gravity) affecting this physic actor
          */
-        void setVerticalForce(float force);
+        void setInertialForce(const Ogre::Vector3 &force);
 
         /**
-         * Gets the current amount of vertical force (gravity) affecting this physic actor
+         * Gets the current amount of inertial force (incl. gravity) affecting this physic actor
          */
-        float getVerticalForce() const;
+        const Ogre::Vector3 &getInertialForce() const
+        {
+            return mForce;
+        }
 
         void setOnGround(bool grounded);
 
-        bool getOnGround() const;
+        bool getOnGround() const
+        {
+            return mCollisionMode && mOnGround;
+        }
 
         btCollisionObject *getCollisionBody() const
         {
@@ -169,9 +175,9 @@ public:
         Ogre::Quaternion mBoxRotation;
         btQuaternion mBoxRotationInverse;
 
-        float verticalForce;
-        bool onGround;
-        bool collisionMode;
+        Ogre::Vector3 mForce;
+        bool mOnGround;
+        bool mCollisionMode;
 
         std::string mMesh;
         std::string mName;