Fix environmental damage sources (#6515)

* Tidy handle damage code
* Fix environmental damage conditions

- Vehicle damage would never occur because it doesn't fire all the
hitpoints
- Missing sanity check on fall damage to check that unit isn't in a
vehicle
- Getting hit by a vehicle while on foot can be detected by checking for
a shooter

* Improve collision handling

- All collisions have a `_shooter` so we simply first check for that because burning doesn't and it could happen at any velocity
- We don't actually care what caused the collision because they should all cause the same type of wounding
- The exception is fall damage because we want to prioritise wounding the legs, we assume if the `_unit` had downward velocity and `_shooter == _unit` that it was fall damage (not necessarily always true, but almost always is and there doesn't look to be a more specific way to check).

addons/medical_engine/functions/fnc_handleDamage.sqf

@@ -1,7 +1,9 @@
 #include "script_component.hpp"
 /*
- * Author: commy2
+ * Author: commy2, SilentSpike
- * Main HandleDamage EH function for soldiers.
+ * HandleDamage EH where wound events are raised based on incoming damage.
+ * Be aware that for each source of damage, the EH can fire multiple times (once for each hitpoint).
+ * We store these incoming damages and compare them on our final hitpoint: "ace_hdbracket".
  *
  * Arguments:
  * Handle damage EH
@@ -13,49 +15,35 @@
  */
 // for travis
 #define HIT_STRUCTURAL QGVAR($#structural)
-#define HIT_CRASH QGVAR($#crash)
 
-params ["_unit", "_selection", "_damage", "_shooter", "_ammo", "_hitPointIndex", "_instigator"];
+params ["_unit", "_selection", "_damage", "_shooter", "_ammo", "_hitPointIndex", "_instigator", "_hitpoint"];
-//diag_log text str _this;
 
 // HD sometimes triggers for remote units - ignore.
-if (!local _unit) exitWith {nil};
+if !(local _unit) exitWith {nil};
 
 // Get missing meta info
-private ["_hitPoint", "_oldDamage"];
+private _oldDamage = 0;
-private _isCrash = false;
 
-// Store
+if (_hitPoint isEqualTo "") then {
-if (_hitPointIndex < 0) then {
     _hitPoint = "#structural";
     _oldDamage = damage _unit;
-
-    // Handle vehicle crashes
-    if (_damage == _unit getVariable [HIT_CRASH, -1]) then {
-        _isCrash = (_ammo == "");
-        _unit setVariable [HIT_CRASH, -1];
-    } else {
-        _unit setVariable [HIT_CRASH, _damage];
-    };
 } else {
-    _hitPoint = toLower (getAllHitPointsDamage _unit select 0 select _hitPointIndex);
     _oldDamage = _unit getHitIndex _hitPointIndex;
-
-    // No crash, reset
-    _unit setVariable [HIT_CRASH, -1];
 };
 
 // Damage can be disabled with old variable or via sqf command allowDamage
 if !(isDamageAllowed _unit && _unit getVariable [QEGVAR(medical,allowDamage), true]) exitWith {_oldDamage};
 
+// Damages are stored for "ace_hdbracket" event triggered last
 private _newDamage = _damage - _oldDamage;
 _unit setVariable [format [QGVAR($%1), _hitPoint], _newDamage];
 
-// These control blood material visuals.
+// Engine damage to these hitpoints controls blood visuals, limping, weapon sway
-// If damage is in dummy hitpoints, "hands" and "legs", don't change anything
+// Handled in fnc_damageBodyPart, persist here
 if (_hitPoint in ["hithead", "hitbody", "hithands", "hitlegs"]) exitWith {_oldDamage};
 
-// Add injury
+// This hitpoint is set to trigger last, evaluate all the stored damage values
+// to determine where wounds are applied
 if (_hitPoint isEqualTo "ace_hdbracket") exitWith {
     _unit setVariable [QGVAR(lastShooter), _shooter];
     _unit setVariable [QGVAR(lastInstigator), _instigator];
@@ -80,10 +68,8 @@ if (_hitPoint isEqualTo "ace_hdbracket") exitWith {
     private _damageLeftLeg = _unit getVariable [QGVAR($HitLeftLeg), 0];
     private _damageRightLeg = _unit getVariable [QGVAR($HitRightLeg), 0];
 
-    // Find hit point that received the maxium damage.
+    // Find hit point that received the maxium damage
-    // second param is a priority. should multiple hitpoints receive the same
+    // Priority used for sorting if incoming damage is equivalent (e.g. max which is 4)
-    // amount of damage (e.g. max which is 4), we don't want them to be sorted
-    // alphabetically (which would mean that RightLeg is always chosen)
     private _allDamages = [
         [_damageHead,     PRIORITY_HEAD,      "Head"],
         [_damageBody,     PRIORITY_BODY,      "Body"],
@@ -97,57 +83,69 @@ if (_hitPoint isEqualTo "ace_hdbracket") exitWith {
     _allDamages sort false;
     (_allDamages select 0) params ["_receivedDamage", "", "_woundedHitPoint"];
 
+    // We know it's structural when no specific hitpoint is damaged
     if (_receivedDamage == 0) then {
         _receivedDamage = _damageStructural;
         _woundedHitPoint = "Body";
     };
-    TRACE_2("received",_receivedDamage,_woundedHitPoint);
 
-    // Check for falling damage.
+    // Environmental damage sources all have empty ammo string
+    // No explicit source given, we infer from differences between them
     if (_ammo isEqualTo "") then {
-        if (velocity _unit select 2 < -2) then {
+        // Any collision with terrain/vehicle/object has a shooter
-            if (_receivedDamage < 0.35) then {
+        // Check this first because burning can happen at any velocity
-                // Less than ~ 5 m
+        if !(isNull _shooter) then {
-                _woundedHitPoint = selectRandom ["LeftLeg", "RightLeg"];
+            _ammo = "#collision";
+
+            /*
+              If shooter != unit then they hit unit, otherwise it could be:
+               - Unit hitting anything at speed
+               - An empty vehicle hitting unit
+               - A physX object hitting unit
+               Assume fall damage for downward velocity because it's most common
+            */
+            if (_shooter == _unit && {(velocity _unit select 2) < -2}) then {
+                _woundedHitPoint = selectRandom ["RightLeg", "LeftLeg"];
+                TRACE_5("Fall",_unit,_shooter,_instigator,_damage,_receivedDamage);
             } else {
-                // More than ~ 5 m
+                _woundedHitPoint = selectRandom ["RightArm", "LeftArm", "RightLeg", "LeftLeg"];
-                _woundedHitPoint = selectRandom ["LeftLeg", "RightLeg", "Body", "Head"];
+                TRACE_5("Collision",_unit,_shooter,_instigator,_damage,_receivedDamage);
+            };
+
+            // Significant damage suggests high relative velocity
+            // Momentum transfers to body/head for worse wounding
+            if (_receivedDamage > 0.35) then {
+                 _woundedHitPoint = selectRandom ["Body", "Head"];
             };
-            _ammo = "#falling";
         } else {
-            if (_receivedDamage > 0.1) then {
+            // Anything else is almost guaranteed to be fire damage
-                // Assume collision damage.
-                _woundedHitPoint = "Body";
-                _ammo = "#vehiclecrash";
-            } else {
-                // Probably fire damage:
             _woundedHitPoint = selectRandom ["LeftLeg", "RightLeg", "Body"];
             _ammo = "#unknown";
+
+            // Fire damage can occur as lots of minor damage events
+            // Combine these until significant enough to wound
             private _combinedDamage = _receivedDamage + (_unit getVariable [QGVAR(trivialDamage), 0]);
             if (_combinedDamage > 0.1) then {
-                    // if the new sum is large enough, reset variable and continue with it added in
                 _unit setVariable [QGVAR(trivialDamage), 0];
-                    TRACE_2("Using sum of trivialDamage",_receivedDamage,_combinedDamage);
                 _receivedDamage = _combinedDamage;
+                TRACE_5("Burning",_unit,_shooter,_instigator,_damage,_receivedDamage);
             } else {
-                    // otherwise just save the new sum into the variable and exit
                 _unit setVariable [QGVAR(trivialDamage), _combinedDamage];
                 _receivedDamage = 0;
             };
         };
     };
-    };
 
-    // Don't trigger for minor damage.
+    // No wounds for minor damage
     if (_receivedDamage > 1E-3) then {
         [QEGVAR(medical,woundReceived), [_unit, _woundedHitPoint, _receivedDamage, _shooter, _ammo]] call CBA_fnc_localEvent;
+        TRACE_2("received",_receivedDamage,_woundedHitPoint);
     };
 
-    // resetting these single-damage-event tracker vars, if we don't do this then
+    // Clear stored damages otherwise they will influence future damage events
-    // subsequent wounds will be piled onto the selection which has accumulated
+    // (aka wounds will pile onto the historically most damaged hitpoint)
-    // the most wounding
     {
-        _unit setVariable [_x, 0];
+        _unit setVariable [_x, nil];
     } forEach [
         QGVAR($HitFace),QGVAR($HitNeck),QGVAR($HitHead),
         QGVAR($HitPelvis),QGVAR($HitAbdomen),QGVAR($HitDiaphragm),QGVAR($HitChest),QGVAR($HitBody),
@@ -157,19 +155,34 @@ if (_hitPoint isEqualTo "ace_hdbracket") exitWith {
     0
 };
 
-// Check for drowning damage.
+// Drowning doesn't fire the EH for each hitpoint so the "ace_hdbracket" code never runs
-// Don't change the third expression. Safe method for FLOATs.
+// Damage occurs in consistent increments
-if (_hitPoint isEqualTo "#structural" && {getOxygenRemaining _unit <= 0.5} && {_damage isEqualTo (_oldDamage + 0.005)}) exitWith {
+if (
+    _hitPoint isEqualTo "#structural" &&
+    {getOxygenRemaining _unit <= 0.5} &&
+    {_damage isEqualTo (_oldDamage + 0.005)}
+) exitWith {
     [QEGVAR(medical,woundReceived), [_unit, "Body", _newDamage, _unit, "#drowning"]] call CBA_fnc_localEvent;
+    TRACE_5("Drowning",_unit,_shooter,_instigator,_damage,_newDamage);
 
     0
 };
 
-// Handle vehicle crashes
+// Crashing a vehicle doesn't fire the EH for each hitpoint so the "ace_hdbracket" code never runs
-if (_isCrash) exitWith {
+// It does fire the EH multiple times, but this seems to scale with the intensity of the crash
+private _vehicle = vehicle _unit;
+if (
+    _hitPoint isEqualTo "#structural" &&
+    {_ammo isEqualTo ""} &&
+    {_vehicle != _unit} &&
+    {vectorMagnitude (velocity _vehicle) > 5}
+    // todo: no way to detect if stationary and another vehicle hits you
+) exitWith {
     [QEGVAR(medical,woundReceived), [_unit, "Body", _newDamage, _unit, "#vehiclecrash"]] call CBA_fnc_localEvent;
+    TRACE_5("Crash",_unit,_shooter,_instigator,_damage,_newDamage);
 
     0
 };
 
+// We store our own damage values so engine damage is unnecessary
 0