Add pre-pass to collision trace function that traces over less distance if possible

apps/openmw/mwphysics/trace.cpp

@@ -12,31 +12,49 @@
 namespace MWPhysics
 {
 
-void ActorTracer::doTrace(const btCollisionObject *actor, const osg::Vec3f& start, const osg::Vec3f& end, const btCollisionWorld* world)
+ActorConvexCallback sweepHelper(const btCollisionObject *actor, const btVector3& from, const btVector3& to, const btCollisionWorld* world, bool actorFilter)
 {
-    const btVector3 btstart = Misc::Convert::toBullet(start);
-    const btVector3 btend = Misc::Convert::toBullet(end);
-
     const btTransform &trans = actor->getWorldTransform();
-    btTransform from(trans);
-    btTransform to(trans);
-    from.setOrigin(btstart);
-    to.setOrigin(btend);
+    btTransform transFrom(trans);
+    btTransform transTo(trans);
+    transFrom.setOrigin(from);
+    transTo.setOrigin(to);
+
+    const btCollisionShape *shape = actor->getCollisionShape();
+    assert(shape->isConvex());
 
-    const btVector3 motion = btstart-btend;
+    const btVector3 motion = from - to; // FIXME: this is backwards; means ActorConvexCallback is doing dot product tests backwards too
     ActorConvexCallback newTraceCallback(actor, motion, btScalar(0.0), world);
     // Inherit the actor's collision group and mask
     newTraceCallback.m_collisionFilterGroup = actor->getBroadphaseHandle()->m_collisionFilterGroup;
     newTraceCallback.m_collisionFilterMask = actor->getBroadphaseHandle()->m_collisionFilterMask;
+    if(actorFilter)
+        newTraceCallback.m_collisionFilterMask &= ~CollisionType_Actor;
 
-    const btCollisionShape *shape = actor->getCollisionShape();
-    assert(shape->isConvex());
-    world->convexSweepTest(static_cast<const btConvexShape*>(shape), from, to, newTraceCallback);
+    world->convexSweepTest(static_cast<const btConvexShape*>(shape), transFrom, transTo, newTraceCallback);
+    return newTraceCallback;
+}
+
+void ActorTracer::doTrace(const btCollisionObject *actor, const osg::Vec3f& start, const osg::Vec3f& end, const btCollisionWorld* world)
+{
+    const btVector3 btstart = Misc::Convert::toBullet(start);
+    btVector3 btend = Misc::Convert::toBullet(end);
+
+    bool do_fallback = false;
+    if((btend-btstart).length2() > 5.0*5.0)
+    {
+        btend = btstart + (btend-btstart).normalized()*5.0;
+        do_fallback = true;
+    }
+
+    auto newTraceCallback = sweepHelper(actor, btstart, btend, world, false);
 
     // Copy the hit data over to our trace results struct:
     if(newTraceCallback.hasHit())
     {
         mFraction = newTraceCallback.m_closestHitFraction;
+        if((end-start).length2() > 0.0)
+            mFraction *= (btend-btstart).length() / (end-start).length();
         mPlaneNormal = Misc::Convert::toOsg(newTraceCallback.m_hitNormalWorld);
         mEndPos = (end-start)*mFraction + start;
         mHitPoint = Misc::Convert::toOsg(newTraceCallback.m_hitPointWorld);
@@ -44,6 +62,22 @@ void ActorTracer::doTrace(const btCollisionObject *actor, const osg::Vec3f& star
     }
     else
     {
+        if(do_fallback)
+        {
+            btend = Misc::Convert::toBullet(end);
+            auto newTraceCallback = sweepHelper(actor, btstart, btend, world, false);
+
+            if(newTraceCallback.hasHit())
+            {
+                mFraction = newTraceCallback.m_closestHitFraction;
+                mPlaneNormal = Misc::Convert::toOsg(newTraceCallback.m_hitNormalWorld);
+                mEndPos = (end-start)*mFraction + start;
+                mHitPoint = Misc::Convert::toOsg(newTraceCallback.m_hitPointWorld);
+                mHitObject = newTraceCallback.m_hitCollisionObject;
+                return;
+            }
+        }
+        // fallthrough
         mEndPos = end;
         mPlaneNormal = osg::Vec3f(0.0f, 0.0f, 1.0f);
         mFraction = 1.0f;
@@ -54,21 +88,7 @@ void ActorTracer::doTrace(const btCollisionObject *actor, const osg::Vec3f& star
 
 void ActorTracer::findGround(const Actor* actor, const osg::Vec3f& start, const osg::Vec3f& end, const btCollisionWorld* world)
 {
-    const btVector3 btstart = Misc::Convert::toBullet(start);
-    const btVector3 btend = Misc::Convert::toBullet(end);
-
-    const btTransform &trans = actor->getCollisionObject()->getWorldTransform();
-    btTransform from(trans.getBasis(), btstart);
-    btTransform to(trans.getBasis(), btend);
-
-    const btVector3 motion = btstart-btend;
-    ActorConvexCallback newTraceCallback(actor->getCollisionObject(), motion, btScalar(0.0), world);
-    // Inherit the actor's collision group and mask
-    newTraceCallback.m_collisionFilterGroup = actor->getCollisionObject()->getBroadphaseHandle()->m_collisionFilterGroup;
-    newTraceCallback.m_collisionFilterMask = actor->getCollisionObject()->getBroadphaseHandle()->m_collisionFilterMask;
-    newTraceCallback.m_collisionFilterMask &= ~CollisionType_Actor;
-
-    world->convexSweepTest(actor->getConvexShape(), from, to, newTraceCallback);
+    auto newTraceCallback = sweepHelper(actor->getCollisionObject(), Misc::Convert::toBullet(start), Misc::Convert::toBullet(end), world, true);
     if(newTraceCallback.hasHit())
     {
         mFraction = newTraceCallback.m_closestHitFraction;