From 2b4d8069257fe307235f430223536a2448ce3613 Mon Sep 17 00:00:00 2001
From: esteldunedain <nicolas.d.badano@gmail.com>
Date: Fri, 3 Apr 2015 18:22:04 -0300
Subject: [PATCH] Reduce or eliminate backblast cause by terrain depending on
 relative slope. Fix #294

---
 .../functions/fnc_getDistance.sqf             | 30 +++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/addons/overpressure/functions/fnc_getDistance.sqf b/addons/overpressure/functions/fnc_getDistance.sqf
index 4fe380fbaf..905ecbd180 100644
--- a/addons/overpressure/functions/fnc_getDistance.sqf
+++ b/addons/overpressure/functions/fnc_getDistance.sqf
@@ -15,15 +15,18 @@
 
 EXPLODE_3_PVT(_this,_posASL,_direction,_maxDistance);
 
-private ["_distance", "_interval", "_line", "_intersections"];
+private ["_distance", "_interval", "_line", "_intersections", "_terrainIntersect", "_lastTerrainIntersect"];
 
 _distance = _maxDistance;
 _interval = _distance;
 _line = [_posASL, []];
+_terrainIntersect = false;
+_lastTerrainIntersect = false;
 
 while {
     _interval > 0.1
 } do {
+    _lastTerrainIntersect = _terrainIntersect;
     _interval = _interval / 2;
 
     _line set [1, _posASL vectorAdd (_direction vectorMultiply _distance)];
@@ -32,9 +35,32 @@ while {
         _x isKindOf "Static" || {_x isKindOf "AllVehicles"}
     } count (lineIntersectsWith _line);
 
-    _distance = _distance + ([1, -1] select (_intersections > 0 || {terrainIntersectASL _line})) * _interval;
+    _terrainIntersect = if (_intersections > 0) then {
+        false
+    } else {
+        terrainIntersectASL _line
+    };
+
+    _distance = _distance + ([1, -1] select (_intersections > 0 || _terrainIntersect)) * _interval;
 
     if (_distance > _maxDistance) exitWith {_distance = 999};
 };
 
+if (_distance > _maxDistance) exitWith {_distance};
+
+// If the intersection was with the terrain, check slope
+if (_terrainIntersect || _lastTerrainIntersect) exitWith {
+    private ["_slope","_angle"];
+    _slope = surfaceNormal (_posASL vectorAdd (_direction vectorMultiply _distance));
+    // Calculate the angle between the terrain and the back blast direction
+    _angle = 90 - acos (- (_slope vectorDotProduct _direction));
+
+    //systemChat format ["Angle: %1", _angle];
+    // Angles is below 25º, no backblast at all
+    if (_angle < 25) exitWith {_distance = 999};
+    // Angles is below 45º the distance is increased according to the difference
+    if (_angle < 45) exitWith {_distance = _distance * (5 - 4 * sqrt ((_angle - 25)/20))};
+    // Angles above 45º create full backblast
+};
+
 _distance