Avoid unnecessary AABB update for rotationally invariant collision shapes

apps/openmw/mwphysics/actor.cpp

@@ -32,9 +32,14 @@ Actor::Actor(const MWWorld::Ptr& ptr, osg::ref_ptr<const Resource::BulletShape>
     if (std::abs(mHalfExtents.x()-mHalfExtents.y())<mHalfExtents.x()*0.05 && mHalfExtents.z() >= mHalfExtents.x())
     {
         mShape.reset(new btCapsuleShapeZ(mHalfExtents.x(), 2*mHalfExtents.z() - 2*mHalfExtents.x()));
+        mRotationallyInvariant = true;
     }
     else
+    {
         mShape.reset(new btBoxShape(toBullet(mHalfExtents)));
+        mRotationallyInvariant = false;
+    }
+
     mConvexShape = static_cast<btConvexShape*>(mShape.get());
 
     mCollisionObject.reset(new btCollisionObject);
@@ -144,6 +149,11 @@ void Actor::updateRotation ()
     updateCollisionObjectPosition();
 }
 
+bool Actor::isRotationallyInvariant() const
+{
+    return mRotationallyInvariant;
+}
+
 void Actor::updateScale()
 {
     float scale = mPtr.getCellRef().getScale();

apps/openmw/mwphysics/actor.hpp

@@ -72,6 +72,11 @@ namespace MWPhysics
         void updateScale();
         void updateRotation();
 
+        /**
+         * Return true if the collision shape looks the same no matter how its Z rotated.
+         */
+        bool isRotationallyInvariant() const;
+
         /**
          * Set mPosition and mPreviousPosition to the position in the Ptr's RefData. This should be used
          * when an object is "instantly" moved/teleported as opposed to being moved by the physics simulation.
@@ -155,6 +160,8 @@ namespace MWPhysics
         bool mCanWaterWalk;
         bool mWalkingOnWater;
 
+        bool mRotationallyInvariant;
+
         std::auto_ptr<btCollisionShape> mShape;
         btConvexShape* mConvexShape;
 

apps/openmw/mwphysics/physicssystem.cpp

@@ -1294,8 +1294,11 @@ namespace MWPhysics
         ActorMap::iterator foundActor = mActors.find(ptr);
         if (foundActor != mActors.end())
         {
-            foundActor->second->updateRotation();
-            mCollisionWorld->updateSingleAabb(foundActor->second->getCollisionObject());
+            if (!foundActor->second->isRotationallyInvariant())
+            {
+                foundActor->second->updateRotation();
+                mCollisionWorld->updateSingleAabb(foundActor->second->getCollisionObject());
+            }
             return;
         }
     }