Expose Minimum LoS Detection Radius (scp-fs2open#6252)

The somewhat modern AI flag for `Require_exact_los` is extremely useful in multiple different situations, for example making large capital ship weapons not fire into friendly surrounding ships on accident. When the feature was added, the `check_los` function was provided with a default value of `10.0` meters for minimum radius detection. This PR exposes that value to modders so they can set it to a reasonable value depending on the ship sizes of their specific needs. And as a note, the los value just uses a simple numerical comparison check, so the los detection could be set to a negative value with no consequence (hence why error messages were not added, though if folks would like I can certainly add them).

code/ai/ai_profiles.cpp

@@ -471,6 +471,10 @@ void parse_ai_profiles_tbl(const char *filename)
 
 				set_flag(profile, "$firing requires exact los:", AI::Profile_Flags::Require_exact_los);
 
+				if (optional_string("$exact los minimum detection radius:")) {
+					stuff_float(&profile->los_min_detection_radius);
+				}
+
 				set_flag(profile, "$fighterbay arrivals use carrier orientation:", AI::Profile_Flags::Fighterbay_arrivals_use_carrier_orient);
 
 				set_flag(profile, "$fighterbay departures use carrier orientation:", AI::Profile_Flags::Fighterbay_departures_use_carrier_orient);
@@ -721,6 +725,7 @@ void ai_profile_t::reset()
 
     flags.reset();
 
+    los_min_detection_radius = 10.0f;
     ai_path_mode = AI_PATH_MODE_NORMAL;
 	subsystem_path_radii = 0;
     bay_arrive_speed_mult = 1.0f;

code/ai/ai_profiles.h

@@ -99,6 +99,9 @@ class ai_profile_t {
 
 	float detail_distance_mult[MAX_DETAIL_LEVEL + 1];	//MAX_DETAIL_LEVEL really needs to be 4
 
+	// minimum radius for the line-of-sight (los) detection --wookieejedi
+	float los_min_detection_radius;
+
 	int ai_path_mode;
 
 	// radii to use for the radius for subsystem path points and default value --wookieejedi

code/ai/aicode.cpp

@@ -6235,7 +6235,7 @@ int ai_fire_primary_weapon(object *objp)
 	weapon_info* wip = &Weapon_info[swp->primary_bank_weapons[swp->current_primary_bank]];
 	if (aip->target_objnum != -1 && (The_mission.ai_profile->flags[AI::Profile_Flags::Require_exact_los] || wip->wi_flags[Weapon::Info_Flags::Require_exact_los])) {
 		//Check if th AI has Line of Sight and is allowed to fire
-		if (!check_los(OBJ_INDEX(objp), aip->target_objnum, 10.0f, swp->current_primary_bank, -1, nullptr)) {
+		if (!check_los(OBJ_INDEX(objp), aip->target_objnum, The_mission.ai_profile->los_min_detection_radius, swp->current_primary_bank, -1, nullptr)) {
 			return 0;
 		}
 	}
@@ -6612,7 +6612,7 @@ bool check_ok_to_fire(int objnum, int target_objnum, const weapon_info *wip, int
 
 		if (The_mission.ai_profile->flags[AI::Profile_Flags::Require_exact_los] || wip->wi_flags[Weapon::Info_Flags::Require_exact_los]) {
 			//Check if th AI has Line of Sight and is allowed to fire
-			if (!check_los(objnum, target_objnum, 10.0f, -1, secondary_bank, firing_pos_global)) {
+			if (!check_los(objnum, target_objnum, The_mission.ai_profile->los_min_detection_radius, -1, secondary_bank, firing_pos_global)) {
 				return false;
 			}
 		}