Fix odd frontline unit spawns

* Modfied frontline vector to ensure start point stays outside of
  exclusion zone.  (Previously it could be up to 100m inside)

* Change randomization in offset distance from frontline to be based
  on a percentage of the unit type's fixed offset instead of the
  width of frontline.
  (Prevents units from being far from their expected distance from
  frontline)

* Change visualgen to use the same frontline vector calculation as the
  unit spawns

game/utils.py

@@ -54,4 +54,4 @@ def heading_sum(h, a) -> int:
         return h
 
 def opposite_heading(h):
-    return h+180
+    return heading_sum(h, 180)

gen/armor.py

@@ -112,12 +112,13 @@ class GroundConflictGenerator:
                 ]
             )
 
-    def _group_point(self, point: Point) -> Point:
+    @staticmethod
+    def _group_point(point: Point, base_distance) -> Point:
         distance = random.randint(
-                int(self.conflict.size * SPREAD_DISTANCE_FACTOR[0]),
-                int(self.conflict.size * SPREAD_DISTANCE_FACTOR[1]),
+                int(base_distance * SPREAD_DISTANCE_FACTOR[0]),
+                int(base_distance * SPREAD_DISTANCE_FACTOR[1]),
                 )
-        return point.random_point_within(distance, self.conflict.size * SPREAD_DISTANCE_SIZE_FACTOR)
+        return point.random_point_within(distance, base_distance * SPREAD_DISTANCE_SIZE_FACTOR)
 
     def generate(self):
         position = Conflict.frontline_position(self.conflict.from_cp, self.conflict.to_cp, self.game.theater)
@@ -495,7 +496,8 @@ class GroundConflictGenerator:
                     group.units[0],
                     len(group.units),
                     final_position,
-                    heading=opposite_heading(spawn_heading)
+                    distance_from_frontline,
+                    heading=opposite_heading(spawn_heading),
                 )
                 if is_player:
                     g.set_skill(self.game.settings.player_skill)
@@ -514,8 +516,9 @@ class GroundConflictGenerator:
         unit: VehicleType,
         count: int,
         at: Point,
+        distance_from_frontline,
         move_formation: PointAction = PointAction.OffRoad,
-        heading=0
+        heading=0,
     ) -> VehicleGroup:
 
         if side == self.conflict.attackers_country:
@@ -527,7 +530,7 @@ class GroundConflictGenerator:
         group = self.mission.vehicle_group(
                 side,
                 namegen.next_unit_name(side, cp.id, unit), unit,
-                position=self._group_point(at),
+                position=self._group_point(at, distance_from_frontline),
                 group_size=count,
                 heading=heading,
                 move_formation=move_formation)

gen/conflictgen.py

@@ -82,24 +82,21 @@ class Conflict:
 
     @classmethod
     def extend_ground_position(cls, initial: Point, max_distance: int, heading: int, theater: ConflictTheater) -> Point:
-        """Finds a valid ground position in one heading from an initial point"""
+        """Finds the first intersection with an exclusion zone in one heading from an initial point up to max_distance"""
         pos = initial
         for distance in range(0, int(max_distance), 100):
-            if not theater.is_on_land(pos):
-                return pos
             pos = initial.point_from_heading(heading, distance)
-        if theater.is_on_land(pos):
-            return pos
-        logging.error("Didn't find ground position ({})!".format(initial))
-        return initial
+            if not theater.is_on_land(pos):
+                return initial.point_from_heading(heading, distance - 100)
+        return pos
 
     @classmethod
     def find_ground_position(cls, initial: Point, max_distance: int, heading: int, theater: ConflictTheater) -> Point:
-        """Finds the nearest ground position along a provided heading and it's inverse"""
+        """Finds the nearest valid ground position along a provided heading and it's inverse"""
         pos = initial
+        if theater.is_on_land(pos):
+            return pos
         for distance in range(0, int(max_distance), 100):
-            if theater.is_on_land(pos):
-                return pos
             pos = initial.point_from_heading(heading, distance)
             if theater.is_on_land(pos):
                 return pos

gen/visualgen.py

@@ -103,15 +103,12 @@ class VisualGenerator:
             if from_cp.is_global or to_cp.is_global:
                 continue
 
-            frontline = Conflict.frontline_position(from_cp, to_cp, self.game.theater)
-            if not frontline:
+            plane_start, heading, distance = Conflict.frontline_vector(from_cp, to_cp, self.game.theater)
+            if not plane_start:
                 continue
 
-            point, heading = frontline
-            plane_start = point.point_from_heading(turn_heading(heading, 90), FRONTLINE_LENGTH / 2)
-
-            for offset in range(0, FRONTLINE_LENGTH, FRONT_SMOKE_SPACING):
-                position = plane_start.point_from_heading(turn_heading(heading, - 90), offset)
+            for offset in range(0, distance, FRONT_SMOKE_SPACING):
+                position = plane_start.point_from_heading(heading, offset)
 
                 for k, v in FRONT_SMOKE_TYPE_CHANCES.items():
                     if random.randint(0, 100) <= k: