Grid-relative movement (#4327)

* Grid-relative movement

Might add a test for it, but not today as it's obvious when it's on / off.

* Comment

Content.Shared/CCVar/CCVars.cs

@@ -175,6 +175,12 @@ namespace Content.Shared.CCVar
          * Physics
          */
 
+        /// <summary>
+        /// When a mob is walking should its X / Y movement be relative to its parent (true) or the map (false).
+        /// </summary>
+        public static readonly CVarDef<bool> RelativeMovement =
+            CVarDef.Create("physics.relative_movement", true, CVar.ARCHIVE | CVar.REPLICATED);
+
         public static readonly CVarDef<float> TileFrictionModifier =
             CVarDef.Create("physics.tile_friction", 40.0f);
 

Content.Shared/Movement/SharedMoverController.cs

@@ -1,7 +1,9 @@
 using Content.Shared.ActionBlocker;
+using Content.Shared.CCVar;
 using Content.Shared.MobState;
 using Content.Shared.Movement.Components;
 using Content.Shared.Pulling.Components;
+using Robust.Shared.Configuration;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
@@ -9,6 +11,7 @@ using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Broadphase;
 using Robust.Shared.Physics.Controllers;
+using Robust.Shared.Utility;
 
 namespace Content.Shared.Movement
 {
@@ -22,10 +25,14 @@ namespace Content.Shared.Movement
 
         private SharedBroadphaseSystem _broadPhaseSystem = default!;
 
+        private bool _relativeMovement;
+
         public override void Initialize()
         {
             base.Initialize();
             _broadPhaseSystem = EntitySystem.Get<SharedBroadphaseSystem>();
+            var configManager = IoCManager.Resolve<IConfigurationManager>();
+            configManager.OnValueChanged(CCVars.RelativeMovement, value => _relativeMovement = value, true);
         }
 
         /// <summary>
@@ -39,12 +46,14 @@ namespace Content.Shared.Movement
             // Target velocity.
             var total = (walkDir * mover.CurrentWalkSpeed + sprintDir * mover.CurrentSprintSpeed);
 
-            if (total != Vector2.Zero)
+            var worldTotal = _relativeMovement ? new Angle(mover.Owner.Transform.Parent!.WorldRotation.Theta).RotateVec(total) : total;
+
+            if (worldTotal != Vector2.Zero)
             {
-                mover.Owner.Transform.LocalRotation = total.GetDir().ToAngle();
+                mover.Owner.Transform.WorldRotation = worldTotal.GetDir().ToAngle();
             }
 
-            physicsComponent.LinearVelocity = total;
+            physicsComponent.LinearVelocity = worldTotal;
         }
 
         /// <summary>
@@ -53,7 +62,8 @@ namespace Content.Shared.Movement
         /// <param name="mover"></param>
         /// <param name="physicsComponent"></param>
         /// <param name="mobMover"></param>
-        protected void HandleMobMovement(IMoverComponent mover, PhysicsComponent physicsComponent, IMobMoverComponent mobMover)
+        protected void HandleMobMovement(IMoverComponent mover, PhysicsComponent physicsComponent,
+            IMobMoverComponent mobMover)
         {
             // TODO: Look at https://gameworksdocs.nvidia.com/PhysX/4.1/documentation/physxguide/Manual/CharacterControllers.html?highlight=controller as it has some adviceo n kinematic controllersx
             if (!UseMobMovement(_broadPhaseSystem, physicsComponent, _mapManager))
@@ -74,30 +84,37 @@ namespace Content.Shared.Movement
 
                 if (!touching)
                 {
-                    transform.LocalRotation = physicsComponent.LinearVelocity.GetDir().ToAngle();
+                    transform.WorldRotation = physicsComponent.LinearVelocity.GetDir().ToAngle();
                     return;
                 }
             }
 
             // Regular movement.
             // Target velocity.
+            // This is relative to the map / grid we're on.
             var total = (walkDir * mover.CurrentWalkSpeed + sprintDir * mover.CurrentSprintSpeed);
 
+            var worldTotal = _relativeMovement ?
+                new Angle(transform.Parent!.WorldRotation.Theta).RotateVec(total) :
+                total;
+
+            DebugTools.Assert(MathHelper.CloseTo(total.Length, worldTotal.Length));
+
             if (weightless)
             {
-                total *= mobMover.WeightlessStrength;
+                worldTotal *= mobMover.WeightlessStrength;
             }
 
-            if (total != Vector2.Zero)
+            if (worldTotal != Vector2.Zero)
             {
                 // This should have its event run during island solver soooo
                 transform.DeferUpdates = true;
-                transform.LocalRotation = total.GetDir().ToAngle();
+                transform.WorldRotation = worldTotal.GetDir().ToAngle();
                 transform.DeferUpdates = false;
                 HandleFootsteps(mover, mobMover);
             }
 
-            physicsComponent.LinearVelocity = total;
+            physicsComponent.LinearVelocity = worldTotal;
         }
 
         public static bool UseMobMovement(SharedBroadphaseSystem broadPhaseSystem, PhysicsComponent body, IMapManager mapManager)