Fixes #869: Added methods to control external and internal collision modes separately

When an actor dies, we should only disable external collisions, i.e. prevent other actors from colliding with the dead body. The dead actor, however, should still have gravity and collision applied.

Also moved disableCollision to when the death animation finishes, not as soon as the actor's health is 0.

apps/openmw/mwmechanics/actors.cpp

@@ -920,9 +920,6 @@ namespace MWMechanics
                     spells.purge(iter->first.getRefData().getHandle());
                 }
 
-                // FIXME: see http://bugs.openmw.org/issues/869
-                MWBase::Environment::get().getWorld()->enableActorCollision(iter->first, false);
-
                 if (iter->second->kill())
                 {
                     ++mDeathCount[cls.getId(iter->first)];
@@ -939,6 +936,8 @@ namespace MWMechanics
                     stats.setMagicEffects(MWMechanics::MagicEffects());
                     calculateCreatureStatModifiers(iter->first, 0);
 
+                    MWBase::Environment::get().getWorld()->enableActorCollision(iter->first, false);
+
                     if (cls.isEssential(iter->first))
                         MWBase::Environment::get().getWindowManager()->messageBox("#{sKilledEssential}");
                 }

apps/openmw/mwworld/physicssystem.cpp

@@ -626,12 +626,12 @@ namespace MWWorld
                 bool cmode = act->getCollisionMode();
                 if(cmode)
                 {
-                    act->enableCollisions(false);
+                    act->enableCollisionMode(false);
                     return false;
                 }
                 else
                 {
-                    act->enableCollisions(true);
+                    act->enableCollisionMode(true);
                     return true;
                 }
             }

apps/openmw/mwworld/worldimp.cpp

@@ -1957,7 +1957,7 @@ namespace MWWorld
     {
         OEngine::Physic::PhysicActor *physicActor = mPhysEngine->getCharacter(actor.getRefData().getHandle());
 
-        physicActor->enableCollisions(enable);
+        physicActor->enableCollisionBody(enable);
     }
 
     bool World::findInteriorPosition(const std::string &name, ESM::Position &pos)

libs/openengine/bullet/physic.cpp

@@ -41,15 +41,18 @@ namespace Physic
         }
     }
 
-    void PhysicActor::enableCollisions(bool collision)
+    void PhysicActor::enableCollisionMode(bool collision)
+    {
+        mCollisionMode = collision;
+    }
+
+    void PhysicActor::enableCollisionBody(bool collision)
     {
         assert(mBody);
         if(collision && !mCollisionMode) enableCollisionBody();
         if(!collision && mCollisionMode) disableCollisionBody();
-        mCollisionMode = collision;
     }
 
-
     void PhysicActor::setPosition(const Ogre::Vector3 &pos)
     {
         assert(mBody);

libs/openengine/bullet/physic.hpp

@@ -99,7 +99,15 @@ namespace Physic
          */
         void setRotation(const Ogre::Quaternion &quat);
 
-        void enableCollisions(bool collision);
+        /**
+         * Sets the collisionMode for this actor. If disabled, the actor can fly and clip geometry.
+         */
+        void enableCollisionMode(bool collision);
+
+        /**
+         * Enables or disables the *external* collision body. If disabled, other actors will not collide with this actor.
+         */
+        void enableCollisionBody(bool collision);
 
         bool getCollisionMode() const
         {