Merge pull request #5732 from Baezon/fix-damaged-engine-max-vel

Fix for ets changes when engines are <15%

code/hud/hudets.cpp

@@ -125,25 +125,32 @@ void update_ets(object* objp, float fl_frametime)
 	//					 This will translate to 71% max speed at 50% engines, and 31% max speed at 10% engines
 	//
 
-	float engine_aggregate_strength;
+	float effective_engine_strength;
+	float actual_engine_strength;
 	if (ship_p->flags[Ship::Ship_Flags::Maneuver_despite_engines]) {
 		// Pretend our strength is 100% when this flag is active
-		engine_aggregate_strength = 1.0f;
+		effective_engine_strength = 1.0f;
+		actual_engine_strength = 1.0f;
 	} else {
-		engine_aggregate_strength = ship_get_subsystem_strength(ship_p, SUBSYSTEM_ENGINE);
+		effective_engine_strength = ship_get_subsystem_strength(ship_p, SUBSYSTEM_ENGINE);
+
+		// very annoying, but ship_get_subsystem_strength will typically cap at no lower than 15% strength reported
+		// causing the condition below to possibly erroneously believe the engine strength isn't changing while being
+		// repaired below that threshold. use the ACTUAL strength for this check
+		actual_engine_strength = ship_get_subsystem_strength(ship_p, SUBSYSTEM_ENGINE, false, true);
 	}
 
 	// only update max speed if engine_aggregate_strength has changed
 	// which helps minimize amount of overrides to max speed
-	if (engine_aggregate_strength != ship_p->prev_engine_aggregate_strength) {
+	if (actual_engine_strength != ship_p->prev_engine_strength) {
 		ets_update_max_speed(objp);
-		ship_p->prev_engine_aggregate_strength = engine_aggregate_strength;
+		ship_p->prev_engine_strength = actual_engine_strength;
 
 		// check if newly updated max speed should be reduced due to engine damage
 		// don't let engine strength affect max speed when playing on lowest skill level
 		if ((objp != Player_obj) || (Game_skill_level > 0)) {
-			if (engine_aggregate_strength < SHIP_MIN_ENGINES_FOR_FULL_SPEED) {
-				objp->phys_info.max_vel.xyz.z *= fl_sqrt(engine_aggregate_strength);
+			if (effective_engine_strength < SHIP_MIN_ENGINES_FOR_FULL_SPEED) {
+				objp->phys_info.max_vel.xyz.z *= fl_sqrt(effective_engine_strength);
 			}
 		}
 	}

code/ship/ship.cpp

@@ -6628,7 +6628,7 @@ void ship::clear()
 	weapon_recharge_index = INTIAL_WEAPON_RECHARGE_INDEX;
 	engine_recharge_index = INTIAL_ENGINE_RECHARGE_INDEX;
 	weapon_energy = 0;
-	prev_engine_aggregate_strength = 1.0f;
+	prev_engine_strength = 1.0f;
 	next_manage_ets = timestamp(0);
 
 	flags.reset();
@@ -14814,7 +14814,7 @@ int ship_find_subsys(ship *sp, const char *ss_name)
 // 0.0 and 1.0 which is the relative combined strength of the given subsystem type.  The number
 // calculated for the engines is slightly different.  Once an engine reaches < 15% of its hits, its
 // output drops to that %.  A dead engine has no output.
-float ship_get_subsystem_strength( ship *shipp, int type, bool skip_dying_check )
+float ship_get_subsystem_strength( ship *shipp, int type, bool skip_dying_check, bool no_minimum_engine_str )
 {
 	float strength;
 	ship_subsys *ssp;
@@ -14847,7 +14847,7 @@ float ship_get_subsystem_strength( ship *shipp, int type, bool skip_dying_check
 				float ratio;
 
 				ratio = ssp->current_hits / ssp->max_hits;
-				if ( ratio < ENGINE_MIN_STR )
+				if ( ratio < ENGINE_MIN_STR && !no_minimum_engine_str)
 					ratio = ENGINE_MIN_STR;
 
 				percent += ratio;

code/ship/ship.h

@@ -645,7 +645,7 @@ class ship
 	int	engine_recharge_index;			// index into array holding the engine recharge rate
 	float	weapon_energy;						// Number of EUs in energy reserves
 	int	next_manage_ets;					// timestamp for when ai can next modify ets ( -1 means never )
-	float prev_engine_aggregate_strength;	// used only in update_ets() to allow for minimizing overrides to max speed --Asteroth and wookieejedi
+	float prev_engine_strength;	// used only in update_ets() to allow for minimizing overrides to max speed --Asteroth and wookieejedi
 
 	flagset<Ship::Ship_Flags>	flags;		// flag variable to contain ship state
 	int	reinforcement_index;				// index into reinforcement struct or -1
@@ -1778,7 +1778,7 @@ extern ship_subsys *ship_get_indexed_subsys(ship *sp, int index);	// returns ind
 extern int ship_find_subsys(ship *sp, const char *ss_name);		// returns numerical index in linked list of subsystems
 extern int ship_get_subsys_index(ship_subsys *subsys);
 
-extern float ship_get_subsystem_strength( ship *shipp, int type, bool skip_dying_check = false );
+extern float ship_get_subsystem_strength( ship *shipp, int type, bool skip_dying_check = false, bool no_minimum_engine_str = false);
 extern ship_subsys *ship_get_subsys(const ship *shipp, const char *subsys_name);
 extern int ship_get_num_subsys(ship *shipp);
 extern ship_subsys *ship_get_closest_subsys_in_sight(ship *sp, int subsys_type, vec3d *attacker_pos);