So, I came in trying to fix gameobject LoS. So I restructured some stuff.

Port From (https://github.com/TrinityCore/TrinityCore/commit/5392212799b669d91c80cf0e9539a3aaa2abbe79)

Source/Framework/Constants/MapConst.cs

@@ -192,4 +192,12 @@ namespace Framework.Constants
         Nothing = 0x00,
         M2 = 0x01
     }
+
+    public enum LineOfSightChecks
+    {
+        Vmap = 0x1, // check static floor layout data
+        Gobject = 0x2, // check dynamic game object data
+
+        All = Vmap | Gobject
+    }
 }

Source/Framework/Constants/SharedConst.cs

@@ -1109,6 +1109,7 @@ namespace Framework.Constants
         ChatStrictLinkCheckingSeverity,
         ChatWhisperLevelReq,
         ChatYellLevelReq,
+        CheckGobjectLos,
         CleanCharacterDb,
         ClientCacheVersion,
         Compression,

Source/Game/Chat/Commands/DebugCommands.cs

@@ -494,8 +494,15 @@ namespace Game.Chat
         {
             Unit unit = handler.GetSelectedUnit();
             if (unit)
-                handler.SendSysMessage("Unit {0} (GuidLow: {1}) is {2}in LoS", unit.GetName(), unit.GetGUID().ToString(), handler.GetSession().GetPlayer().IsWithinLOSInMap(unit) ? "" : "not ");
+            {
-            return true;
+                Player player = handler.GetSession().GetPlayer();
+                handler.SendSysMessage($"Checking LoS {player.GetName()} -> {unit.GetName()}:");
+                handler.SendSysMessage($"    VMAP LoS: {(player.IsWithinLOSInMap(unit, LineOfSightChecks.Vmap) ? "clear" : "obstructed")}");
+                handler.SendSysMessage($"    GObj LoS: {(player.IsWithinLOSInMap(unit, LineOfSightChecks.Gobject) ? "clear" : "obstructed")}");
+                handler.SendSysMessage($"{unit.GetName()} is {(player.IsWithinLOSInMap(unit) ? "" : "not ")}in line of sight of {player.GetName()}.");
+                return true;
+            }
+            return false;
         }
 
         [Command("moveflags", RBACPermissions.CommandDebugMoveflags)]

Source/Game/Entities/Object/WorldObject.cs

@@ -1806,20 +1806,6 @@ namespace Game.Entities
                 return thisOrTransport.IsInDist2d(objOrObjTransport, maxdist);
         }
 
-        public bool IsWithinLOSInMap(WorldObject obj, ModelIgnoreFlags ignoreFlags = ModelIgnoreFlags.Nothing)
-        {
-            if (!IsInMap(obj))
-                return false;
-
-            float x, y, z;
-            if (obj.IsTypeId(TypeId.Player))
-                obj.GetPosition(out x, out y, out z);
-            else
-                obj.GetHitSpherePointFor(GetPosition(), out x, out y, out z);
-
-            return IsWithinLOS(x, y, z, ignoreFlags);
-        }
-
         public float GetDistance(WorldObject obj)
         {
             float d = GetExactDist(obj.GetPosition()) - GetCombatReach() - obj.GetCombatReach();
@@ -1895,7 +1881,7 @@ namespace Game.Entities
             return obj && IsInMap(obj) && IsInPhase(obj) && _IsWithinDist(obj, dist2compare, is3D, incOwnRadius, incTargetRadius);
         }
 
-        public bool IsWithinLOS(float ox, float oy, float oz, ModelIgnoreFlags ignoreFlags = ModelIgnoreFlags.Nothing)
+        public bool IsWithinLOS(float ox, float oy, float oz, LineOfSightChecks checks = LineOfSightChecks.All, ModelIgnoreFlags ignoreFlags = ModelIgnoreFlags.Nothing)
         {
             if (IsInWorld)
             {
@@ -1905,12 +1891,26 @@ namespace Game.Entities
                 else
                     GetHitSpherePointFor(new Position(ox, oy, oz), out x, out y, out z);
 
-                return GetMap().IsInLineOfSight(GetPhaseShift(), x, y, z + 2.0f, ox, oy, oz + 2.0f, ignoreFlags);
+                return GetMap().IsInLineOfSight(GetPhaseShift(), x, y, z + 2.0f, ox, oy, oz + 2.0f, checks, ignoreFlags);
             }
 
             return true;
         }
 
+        public bool IsWithinLOSInMap(WorldObject obj, LineOfSightChecks checks = LineOfSightChecks.All, ModelIgnoreFlags ignoreFlags = ModelIgnoreFlags.Nothing)
+        {
+            if (!IsInMap(obj))
+                return false;
+
+            float x, y, z;
+            if (obj.IsTypeId(TypeId.Player))
+                obj.GetPosition(out x, out y, out z);
+            else
+                obj.GetHitSpherePointFor(GetPosition(), out x, out y, out z);
+
+            return IsWithinLOS(x, y, z, checks, ignoreFlags);
+        }
+
         Position GetHitSpherePointFor(Position dest)
         {
             Vector3 vThis = new Vector3(GetPositionX(), GetPositionY(), GetPositionZ());

Source/Game/Maps/Map.cs

@@ -2204,10 +2204,15 @@ namespace Game.Maps
             return 0;
         }
 
-        public bool IsInLineOfSight(PhaseShift phaseShift, float x1, float y1, float z1, float x2, float y2, float z2, ModelIgnoreFlags ignoreFlags)
+        public bool IsInLineOfSight(PhaseShift phaseShift, float x1, float y1, float z1, float x2, float y2, float z2, LineOfSightChecks checks, ModelIgnoreFlags ignoreFlags)
         {
-            return Global.VMapMgr.IsInLineOfSight(PhasingHandler.GetTerrainMapId(phaseShift, this, x1, y1), x1, y1, z1, x2, y2, z2, ignoreFlags)
+            if (checks.HasAnyFlag(LineOfSightChecks.Vmap) && Global.VMapMgr.IsInLineOfSight(PhasingHandler.GetTerrainMapId(phaseShift, this, x1, y1), x1, y1, z1, x2, y2, z2, ignoreFlags))
-                   && _dynamicTree.IsInLineOfSight(new Vector3(x1, y1, z1), new Vector3(x2, y2, z2), phaseShift);
+                return false;
+
+            if (WorldConfig.GetBoolValue(WorldCfg.CheckGobjectLos) && checks.HasAnyFlag(LineOfSightChecks.Gobject) && _dynamicTree.IsInLineOfSight(new Vector3(x1, y1, z1), new Vector3(x2, y2, z2), phaseShift))
+                return false;
+
+            return true;
         }
 
         public bool GetObjectHitPos(PhaseShift phaseShift, float x1, float y1, float z1, float x2, float y2, float z2, out float rx, out float ry, out float rz, float modifyDist)

Source/Game/Server/WorldConfig.cs

@@ -916,6 +916,9 @@ namespace Game
             Values[WorldCfg.CreatureCheckInvalidPostion] = GetDefaultValue("Creature.CheckInvalidPosition", false);
             Values[WorldCfg.GameobjectCheckInvalidPostion] = GetDefaultValue("GameObject.CheckInvalidPosition", false);
 
+            // Whether to use LoS from game objects
+            Values[WorldCfg.CheckGobjectLos] = GetDefaultValue("CheckGameObjectLoS", true);
+
             // call ScriptMgr if we're reloading the configuration
             if (reload)
                 Global.ScriptMgr.OnConfigLoad(reload);

Source/Game/Spells/Spell.cs

@@ -1452,7 +1452,7 @@ namespace Game.Spells
                         if (unitTarget != null)
                         {
                             uint deficit = (uint)(unitTarget.GetMaxHealth() - unitTarget.GetHealth());
-                            if ((deficit > maxHPDeficit || found == null) && target.IsWithinDist(unitTarget, jumpRadius) && target.IsWithinLOSInMap(unitTarget, ModelIgnoreFlags.M2))
+                            if ((deficit > maxHPDeficit || found == null) && target.IsWithinDist(unitTarget, jumpRadius) && target.IsWithinLOSInMap(unitTarget, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                             {
                                 found = obj;
                                 maxHPDeficit = deficit;
@@ -1467,10 +1467,10 @@ namespace Game.Spells
                     {
                         if (found == null)
                         {
-                            if ((!isBouncingFar || target.IsWithinDist(obj, jumpRadius)) && target.IsWithinLOSInMap(obj, ModelIgnoreFlags.M2))
+                            if ((!isBouncingFar || target.IsWithinDist(obj, jumpRadius)) && target.IsWithinLOSInMap(obj, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                                 found = obj;
                         }
-                        else if (target.GetDistanceOrder(obj, found) && target.IsWithinLOSInMap(obj, ModelIgnoreFlags.M2))
+                        else if (target.GetDistanceOrder(obj, found) && target.IsWithinLOSInMap(obj, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                             found = obj;
                     }
                 }
@@ -4643,7 +4643,7 @@ namespace Game.Spells
                         }
 
                         if (!m_spellInfo.HasAttribute(SpellAttr2.CanTargetNotInLos) && !Global.DisableMgr.IsDisabledFor(DisableType.Spell, m_spellInfo.Id, null, DisableFlags.SpellLOS)
-                            && !unitTarget.IsWithinLOSInMap(losTarget, ModelIgnoreFlags.M2))
+                            && !unitTarget.IsWithinLOSInMap(losTarget, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                             return SpellCastResult.LineOfSight;
                     }
                 }
@@ -4656,7 +4656,7 @@ namespace Game.Spells
                 m_targets.GetDstPos().GetPosition(out x, out y, out z);
 
                 if (!m_spellInfo.HasAttribute(SpellAttr2.CanTargetNotInLos) && !Global.DisableMgr.IsDisabledFor(DisableType.Spell, m_spellInfo.Id, null, DisableFlags.SpellLOS)
-                    && !m_caster.IsWithinLOS(x, y, z, ModelIgnoreFlags.M2))
+                    && !m_caster.IsWithinLOS(x, y, z, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                     return SpellCastResult.LineOfSight;
             }
 
@@ -6594,7 +6594,7 @@ namespace Game.Spells
                     {
                         if (m_targets.GetCorpseTargetGUID().IsEmpty())
                         {
-                            if (target.IsWithinLOSInMap(m_caster, ModelIgnoreFlags.M2) && target.HasUnitFlag(UnitFlags.Skinnable))
+                            if (target.IsWithinLOSInMap(m_caster, LineOfSightChecks.All, ModelIgnoreFlags.M2) && target.HasUnitFlag(UnitFlags.Skinnable))
                                 return true;
 
                             return false;
@@ -6610,7 +6610,7 @@ namespace Game.Spells
                         if (!corpse.HasDynamicFlag(UnitDynFlags.Lootable))
                             return false;
 
-                        if (!corpse.IsWithinLOSInMap(m_caster, ModelIgnoreFlags.M2))
+                        if (!corpse.IsWithinLOSInMap(m_caster, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                             return false;
 
                         break;
@@ -6618,7 +6618,7 @@ namespace Game.Spells
                 default:
                     {
                         if (losPosition != null)
-                            return target.IsWithinLOS(losPosition.GetPositionX(), losPosition.GetPositionY(), losPosition.GetPositionZ(), ModelIgnoreFlags.M2);
+                            return target.IsWithinLOS(losPosition.GetPositionX(), losPosition.GetPositionY(), losPosition.GetPositionZ(), LineOfSightChecks.All, ModelIgnoreFlags.M2);
                         else
                         {
                             // Get GO cast coordinates if original caster -> GO
@@ -6627,7 +6627,7 @@ namespace Game.Spells
                                 caster = m_caster.GetMap().GetGameObject(m_originalCasterGUID);
                             if (!caster)
                                 caster = m_caster;
-                            if (target != m_caster && !target.IsWithinLOSInMap(caster, ModelIgnoreFlags.M2))
+                            if (target != m_caster && !target.IsWithinLOSInMap(caster, LineOfSightChecks.All, ModelIgnoreFlags.M2))
                                 return false;
                         }
 

Source/WorldServer/WorldServer.conf.dist

@@ -410,6 +410,15 @@ vmap.EnableIndoorCheck = 1
 
 DetectPosCollision = 1
 
+#
+#    CheckGameObjectLoS
+#        Description: Include dynamic game objects (doors, chests etc.) in line of sight checks.
+#                     This increases CPU usage somewhat.
+#        Default:     1 - (Enabled)
+#                     0 - (Disabled, may break some boss encounters)
+
+CheckGameObjectLoS = 1
+
 #
 #    TargetPosRecalculateRange
 #        Description: Max distance from movement target point (+moving unit size) and targeted

sql/updates/world/master/2020_07_16_02_world_2017_06_10_00_world.sql

@@ -0,0 +1 @@
+DELETE FROM `spell_script_names` WHERE `ScriptName`='spell_sapphiron_frost_breath';