Fix L’Hiver Mod: Monster HP sometimes increases during a fight

game/world/objects/npc.cpp

@@ -2296,16 +2296,22 @@ void Npc::tickTimedEvt(Animation::EvCount& ev) {
   }
 
 void Npc::tickRegen(int32_t& v, const int32_t max, const int32_t chg, const uint64_t dt) {
-  uint64_t tick = owner.tickCount();
+  const uint64_t tick = owner.tickCount();
   if(tick<dt || chg==0)
     return;
-  int32_t time0 = int32_t(tick%1000);
-  int32_t time1 = time0+int32_t(dt);
-
-  int32_t val0 = (time0*chg)/1000;
-  int32_t val1 = (time1*chg)/1000;
+  // ATR_REGENERATE* is an interval: 1 point per 'chg' seconds.
+  // treating it as points-per-second made monsters in mods with hp-regeneration (L'Hiver)
+  // heal faster than the player can deal damage
+  const uint64_t amount = chg>0 ? uint64_t(chg) : uint64_t(-int64_t(chg));
+  const uint64_t period = amount*1000u;
+  const uint64_t prev   = tick-dt;
+  const uint64_t n      = tick/period-prev/period;
+  if(n==0)
+    return;
 
-  int32_t nextV = std::max(0,std::min(v+val1-val0,max));
+  const int64_t step  = chg>0 ? int64_t(n) : -int64_t(n);
+  const int64_t upper = std::max<int64_t>(0,max);
+  int32_t nextV = int32_t(std::clamp<int64_t>(int64_t(v)+step,0,upper));
   if(v!=nextV) {
     v = nextV;
     // check health, in case of negative chg
@@ -4662,16 +4668,26 @@ bool Npc::canRayHitPoint(const Tempest::Vec3 self, const Tempest::Vec3 pos, floa
   if(qDistTo(pos)>range*range)
     return false;
 
-  static const double ref = std::cos(100*M_PI/180.0); // spec requires +-100 view angle range
+  // The vector below points from the target back to this NPC. A >=100 degree separation from
+  // that reverse vector is the intended <=80 degree front arc.
+  static const double ref = std::cos(100*M_PI/180.0);
   const DynamicWorld* w   = owner.physic();
   bool freeLos = angOverride>=180.f;
   if(freeLos) {
     return !w->ray(self, pos).hasCol;
     }
 
-  float dx  = self.x-pos.x, dz=self.z-pos.z;
+  // cone from the object position, not the animated head bone: in melee the head dives into
+  // the target and the direction to it collapses to noise. a false negative here reads to some
+  // mods as a point-blank stealth hit and triggers a monster self-heal.
+  float dx  = x-pos.x, dz = z-pos.z;
   float dir = angleDir(dx,dz);
-  float da  = float(M_PI)*(visual.viewDirection()-dir)/180.f;
+
+  // Use the logical heading during normal movement/combat. While attached to a MOBSI the
+  // interaction animation owns the root rotation, so the visible pose remains authoritative.
+  // Flying monsters are not in that state and their model yaw must not flip the cone.
+  float viewAng = (interactive()!=nullptr) ? visual.viewDirection() : angle;
+  float da  = float(M_PI)*(viewAng-dir)/180.f;
   auto  ca  = angOverride > 0 ? std::cos(angOverride*M_PI/180.0) : ref;
   if(double(std::cos(da))<=ca) {
     if(!w->ray(self, pos).hasCol)