Merge branch 'fix-actor-sim-when-idle' into 'master'

Fix actor simulation running when completely idle

Closes #5862

See merge request OpenMW/openmw!4105

apps/openmw/mwphysics/movementsolver.cpp

@@ -139,17 +139,43 @@ namespace MWPhysics
             return;
         }
 
+        // Physics simulation can be potentially skipped if all conditions match:
+        //   - Actor is on ground
+        //   - Actor is not flying
+        //   - mIsAquatic is false
+        //   - mMovement is a zero vector
+        //   - mInertia is a zero vector
+        // This is important to fix #3803 and others
+        ActorTracer tracer;
+        if (!actor.mFlying && actor.mIsOnGround && !actor.mIsAquatic && actor.mMovement.length2() == 0
+            && actor.mInertia.length2() == 0)
+        {
+            // We think we can skip the simulation, but we must double check to cover edge cases
+            // trace the actor's collision object down to try and find valid ground to stand on
+            // the ground could be removed from the actor, so we cant just remember the last ground value
+            // we must also check if walking on water even if we skip this movement simulation
+            // the simulation can also only be skipped if it finds solid ground, not an actor or unwalkable slope
+            const osg::Vec3f from = actor.mPosition + osg::Vec3f(0.0f, 0.0f, actor.mHalfExtentsZ);
+            const auto dropDistance = 2 * sGroundOffset + (actor.mIsOnGround ? sStepSizeDown : 0);
+            const osg::Vec3f to = from - osg::Vec3f(0, 0, dropDistance);
+            tracer.doTrace(actor.mCollisionObject, from, to, collisionWorld, actor.mIsOnGround);
+            if (tracer.mFraction < 1.0f && !isActor(tracer.mHitObject) && isWalkableSlope(tracer.mPlaneNormal))
+            {
+                actor.mStandingOn = tracer.mHitObject;
+                actor.mWalkingOnWater
+                    = actor.mStandingOn->getBroadphaseHandle()->m_collisionFilterGroup == CollisionType_Water;
+                return;
+            }
+        }
+
         // Adjust for collision mesh offset relative to actor's "location"
         // (doTrace doesn't take local/interior collision shape translation into account, so we have to do it on our
         // own) for compatibility with vanilla assets, we have to derive this from the vertical half extent instead of
         // from internal hull translation if not for this hack, the "correct" collision hull position would be
         // physicActor->getScaledMeshTranslation()
         actor.mPosition.z() += actor.mHalfExtentsZ; // vanilla-accurate
-
         float swimlevel = actor.mSwimLevel + actor.mHalfExtentsZ;
 
-        ActorTracer tracer;
-
         osg::Vec3f velocity;
 
         // Dead and paralyzed actors underwater will float to the surface,

apps/openmw/mwworld/worldimp.cpp

@@ -1331,19 +1331,21 @@ namespace MWWorld
             return;
         }
 
+        const bool isActor = ptr.getClass().isActor();
         const float terrainHeight = ptr.getCell()->isExterior()
             ? getTerrainHeightAt(pos, ptr.getCell()->getCell()->getWorldSpace())
             : -std::numeric_limits<float>::max();
-        pos.z() = std::max(pos.z(), terrainHeight)
-            + 20; // place slightly above terrain. will snap down to ground with code below
+        pos.z() = std::max(pos.z(), terrainHeight);
 
         // We still should trace down dead persistent actors - they do not use the "swimdeath" animation.
-        bool swims = ptr.getClass().isActor() && isSwimming(ptr)
+        bool swims = isActor && isSwimming(ptr)
             && !(ptr.getClass().isPersistent(ptr) && ptr.getClass().getCreatureStats(ptr).isDeathAnimationFinished());
-        if (force || !ptr.getClass().isActor() || (!isFlying(ptr) && !swims && isActorCollisionEnabled(ptr)))
+        if (force || !isActor || (!isFlying(ptr) && !swims && isActorCollisionEnabled(ptr)))
         {
-            osg::Vec3f traced
-                = mPhysics->traceDown(ptr, pos, ESM::getCellSize(ptr.getCell()->getCell()->getWorldSpace()));
+            // place slightly above terrain. will snap down to ground with code below
+            const osg::Vec3f posAdjusted = pos + osg::Vec3f(0.0f, 0.0f, 20.0f);
+            const osg::Vec3f traced
+                = mPhysics->traceDown(ptr, posAdjusted, ESM::getCellSize(ptr.getCell()->getCell()->getWorldSpace()));
             pos.z() = std::min(pos.z(), traced.z());
         }