Expand collision avoidance to strafing (#6789)

Currently, the `$better combat collision avoidance for fightercraft:` flag only checks for possible big ship collisions when in normal chase mode (`AIM_CHASE`), but strafing a big ship is a separate AI mode (`AIM_STRAFE`). Per discussion with Asteroth, strafe attacking should also check for better collision avoidance, as the modder likely would expect that to fall under this AI flag. Also took the chance to make the collision avoidance check into a function to improve maintenance and usability.

Author: wookieejedi

code/ai/aibig.cpp

@@ -864,7 +864,7 @@ void ai_big_chase_ct()
 extern bool ai_select_secondary_weapon(object *objp, ship_weapon *swp, int priority1 = -1, int priority2 = -1);
 extern float set_secondary_fire_delay(ai_info *aip, ship *shipp, weapon_info *swip, bool burst);
 extern bool ai_choose_secondary_weapon(object *objp, ai_info *aip, object *en_objp);
-extern int maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vec3d *goal_point, float delta_time, float time_scale = 1.f);
+extern bool maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vec3d *goal_point, float delta_time, float time_scale = 1.f);
 
 extern void maybe_cheat_fire_synaptic(object *objp);
 

code/ai/aicode.cpp

@@ -7678,7 +7678,7 @@ void mabs_pick_goal_point(object *objp, object *big_objp, vec3d *collision_point
 /**
  * Return true if a large ship is being ignored.
  */
-int maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vec3d *goal_point, float delta_time, float time_scale = 1.f)
+bool maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vec3d *goal_point, float delta_time, float time_scale = 1.f)
 {
 	if (timestamp_elapsed(aip->avoid_check_timestamp)) {
 		float		distance;
@@ -7713,10 +7713,30 @@ int maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vec3d
 		if (ai_willing_to_afterburn_hard(aip) && dot > 0.99f)
 			ai_afterburn_hard(Pl_objp, aip);
 
-		return 1;
+		return true;
 	}
 
-	return 0;
+	return false;
+}
+
+/**
+ * Return true if small ship and it will likely collide with large ship
+ * developed by Asteroth
+ */
+bool better_collision_avoidance_triggered(bool flag_to_check, float avoidance_aggression, object* pl_objp, object* en_objp)
+{
+	ship* shipp = &Ships[pl_objp->instance];
+	ship_info* sip = &Ship_info[shipp->ship_info_index];
+
+	if ((flag_to_check) && sip->is_small_ship()) {
+		vec3d collide_vec = pl_objp->phys_info.vel * (avoidance_aggression / (PI2 / sip->srotation_time));
+		float radius_contribution = (pl_objp->phys_info.speed + pl_objp->radius) / pl_objp->phys_info.speed;
+		collide_vec *= radius_contribution;
+
+		collide_vec += pl_objp->pos;
+		return (maybe_avoid_big_ship(pl_objp, en_objp, &Ai_info[shipp->ai_index], &collide_vec, 0.f, 0.1f));
+	}
+	return false;
 }
 
 /**
@@ -8941,14 +8961,11 @@ void ai_chase()
 		return;
 	}
 
-	if ((The_mission.ai_profile->flags[AI::Profile_Flags::Better_combat_collision_avoidance]) && sip->is_small_ship()) {
-		vec3d collide_vec = Pl_objp->phys_info.vel * (The_mission.ai_profile->better_collision_avoid_aggression_combat / (PI2 / sip->srotation_time));
-		float radius_contribution = (Pl_objp->phys_info.speed + Pl_objp->radius) / Pl_objp->phys_info.speed;
-		collide_vec *= radius_contribution;
-
-		collide_vec += Pl_objp->pos;
-		if (maybe_avoid_big_ship(Pl_objp, En_objp, aip, &collide_vec, 0.f, 0.1f))
-			return;
+	if (better_collision_avoidance_triggered(
+			The_mission.ai_profile->flags[AI::Profile_Flags::Better_combat_collision_avoidance],
+			The_mission.ai_profile->better_collision_avoid_aggression_combat,
+			Pl_objp, En_objp)) {
+		return;
 	}
 
 	if (enemy_sip_flags.any_set()) {
@@ -10862,16 +10879,11 @@ void ai_guard()
 		return;
 	}
 
-	ship_info* sip = &Ship_info[shipp->ship_info_index];
-	if ((The_mission.ai_profile->flags[AI::Profile_Flags::Better_guard_collision_avoidance]) && sip->is_small_ship()) {
-
-		vec3d collide_vec = Pl_objp->phys_info.vel * (The_mission.ai_profile->better_collision_avoid_aggression_guard / (PI2 / sip->srotation_time));
-		float radius_contribution = (Pl_objp->phys_info.speed + Pl_objp->radius) / Pl_objp->phys_info.speed;
-		collide_vec *= radius_contribution;
-
-		collide_vec += Pl_objp->pos;
-		if (maybe_avoid_big_ship(Pl_objp, En_objp, aip, &collide_vec, 0.f, 0.1f))
-			return;
+	if (better_collision_avoidance_triggered(
+			The_mission.ai_profile->flags[AI::Profile_Flags::Better_guard_collision_avoidance],
+			The_mission.ai_profile->better_collision_avoid_aggression_guard,
+			Pl_objp, En_objp)) {
+		return;
 	}
 
 	// handler for guard object with BIG radius
@@ -14153,7 +14165,12 @@ void ai_execute_behavior(ai_info *aip)
 	case AIM_STRAFE:
 		if (En_objp) {
 			Assert(En_objp->type == OBJ_SHIP);
-			ai_big_strafe();	// strafe a big ship
+			if (!(better_collision_avoidance_triggered(
+					The_mission.ai_profile->flags[AI::Profile_Flags::Better_combat_collision_avoidance],
+					The_mission.ai_profile->better_collision_avoid_aggression_combat,
+					Pl_objp, En_objp))) {
+				ai_big_strafe();	// strafe a big ship
+			}
 		} else {
 			aip->mode = AIM_NONE;
 		}