Fix regression caused by Interkarma#1861

nuking themselves with spells at range in the presence of low obstacles.

A side effect of this PR however, is that daedra lords in the "crossbow
room" near the end of Mantellan Crux stopped shooting at the player
altogether, making this room much less threatening.

This new PR checks for obstacles a bit in front of the enemies, so they
can still cast from behind thin obstacles (rationale: spells start from
arm's reach). It's a bit crude, for example it doesn't change from where
the spells will be really cast, but from testing different casters
(namely, beside Mantellan Crux's daedra lords: Karolys lich and
Gortwog's shaman in entrance of Orsinium), I haven't experienced
regressions.

Assets/Scripts/Game/EnemyMotor.cs

@@ -35,6 +35,7 @@ public class EnemyMotor : MonoBehaviour
         const float attackSpeedDivisor = 2f;        // How much to slow down during attack animations
         float stopDistance = 1.7f;                  // Used to prevent orbiting
         const float doorCrouchingHeight = 1.65f;    // How low enemies dive to pass thru doors
+        const float armLength = 1f;                 // Distance of cast spells origin
         bool flies;                                 // The enemy can fly
         bool swims;                                 // The enemy can swim
         bool pausePursuit;                          // pause to wait for the player to come closer to ground
@@ -677,6 +678,9 @@ bool HasClearPathToShootProjectile(float speed, float radius)
             if (sphereCastDir == EnemySenses.ResetPlayerPos)
                 return false;
 
+            float sphereCastDist = (sphereCastDir - transform.position).magnitude;
+            sphereCastDir = (sphereCastDir - transform.position).normalized;
+
             // No point blank shooting special handling here, makes enemies favor other attack types (melee, touch spells,...)
 
             bool myColliderWasEnabled = false;
@@ -686,16 +690,13 @@ bool HasClearPathToShootProjectile(float speed, float radius)
                 // Exclude enemy collider from CheckSphere test
                 myCollider.enabled = false;
             }
-            bool isSpaceInsufficient = Physics.CheckSphere(transform.position, radius, ignoreMaskForShooting);
+            bool isSpaceInsufficient = Physics.CheckSphere(transform.position + sphereCastDir * armLength, radius, ignoreMaskForShooting);
             if (myCollider)
                 myCollider.enabled = myColliderWasEnabled;
 
             if (isSpaceInsufficient)
                 return false;
 
-            float sphereCastDist = (sphereCastDir - transform.position).magnitude;
-            sphereCastDir = (sphereCastDir - transform.position).normalized;
-
             RaycastHit hit;
             if (Physics.SphereCast(transform.position, radius, sphereCastDir, out hit, sphereCastDist, ignoreMaskForShooting))
             {