Added trail property for ammo effects

data/json/ammo_effects.json

@@ -89,7 +89,8 @@
   {
     "id": "PLASMA",
     "type": "ammo_effect",
-    "aoe": { "field_type": "fd_plasma", "intensity_min": 2, "intensity_max": 3, "chance": 2 }
+    "aoe": { "field_type": "fd_plasma", "intensity_min": 2, "intensity_max": 3, "chance": 2 },
+    "trail": { "field_type": "fd_plasma", "intensity_min": 1, "intensity_max": 2, "chance": 50 }
   },
   {
     "id": "EXPLOSIVE_HUGE",
@@ -150,5 +151,45 @@
     "id": "EMP",
     "type": "ammo_effect",
     "do_emp_blast": true
+  },
+  {
+    "id": "TRAIL",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_smoke", "intensity_min": 1, "intensity_max": 2, "chance": 75 }
+  },
+  {
+    "id": "STREAM",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_fire", "intensity_min": 1, "intensity_max": 2, "chance": 66 }
+  },
+  {
+    "id": "STREAM_BIG",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_fire", "intensity_min": 2, "intensity_max": 2, "chance": 75 }
+  },
+  {
+    "id": "STREAM_GAS_FUNGICIDAL",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_fungicidal_gas", "intensity_min": 1, "intensity_max": 2, "chance": 66 }
+  },
+  {
+    "id": "STREAM_GAS_INSCENTICIDAL",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_insecticidal_gas", "intensity_min": 1, "intensity_max": 2, "chance": 66 }
+  },
+  {
+    "id": "LIGHTNING",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_electricity", "intensity_min": 2, "intensity_max": 3 }
+  },
+  {
+    "id": "LASER",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_laser", "intensity_min": 2, "intensity_max": 2 }
+  },
+  {
+    "id": "DRAW_LASER_BEAM",
+    "type": "ammo_effect",
+    "trail": { "field_type": "fd_laser", "intensity_min": 2, "intensity_max": 2 }
   }
 ]

src/ammo_effect.cpp

@@ -73,6 +73,13 @@ void ammo_effect::load( const JsonObject &jo, const std::string & )
         optional( joa, was_loaded, "check_sees", aoe_check_sees, false );
         optional( joa, was_loaded, "check_sees_radius", aoe_check_sees_radius, 0 );
     }
+    if( jo.has_member( "trail" ) ) {
+        JsonObject joa = jo.get_object( "trail" );
+        optional( joa, was_loaded, "field_type", trail_field_type_name, "fd_null" );
+        optional( joa, was_loaded, "intensity_min", trail_intensity_min, 0 );
+        optional( joa, was_loaded, "intensity_max", trail_intensity_max, 0 );
+        optional( joa, was_loaded, "chance", trail_chance, 1 );
+    }
     if( jo.has_member( "explosion" ) ) {
         JsonObject joe = jo.get_object( "explosion" );
         aoe_explosion_data = load_explosion_data( joe );
@@ -85,6 +92,7 @@ void ammo_effect::finalize()
 {
     for( const ammo_effect &ae : ammo_effects::get_all() ) {
         const_cast<ammo_effect &>( ae ).aoe_field_type = field_type_id( ae.aoe_field_type_name );
+        const_cast<ammo_effect &>( ae ).trail_field_type = field_type_id( ae.trail_field_type_name );
     }
 
 }
@@ -112,6 +120,19 @@ void ammo_effect::check() const
     if( aoe_intensity_max < aoe_intensity_min ) {
         debugmsg( "Maximum intensity must be greater than or equal to minimum intensity" );
     }
+    if( !trail_field_type.is_valid() ) {
+        debugmsg( "No such field type %s", trail_field_type_name );
+    }
+    if( trail_chance > 100 || trail_chance <= 0 ) {
+        debugmsg( "Field chance divisor cannot be negative" );
+        debugmsg( "Field chance of %s out of range (%d of min 1 max 100)", id.c_str(), trail_chance );
+    }
+    if( trail_intensity_min < 0 ) {
+        debugmsg( "Field intensity cannot be negative" );
+    }
+    if( trail_intensity_max < trail_intensity_min ) {
+        debugmsg( "Maximum intensity must be greater than or equal to minimum intensity" );
+    }
 }
 
 size_t ammo_effect::count()

src/ammo_effect.h

@@ -35,6 +35,13 @@ struct ammo_effect {
         bool do_flashbang = false;
         bool do_emp_blast = false;
 
+        field_type_id trail_field_type = fd_null;
+        /** used during JSON loading only */
+        std::string trail_field_type_name = "fd_null";
+        int trail_intensity_min = 0;
+        int trail_intensity_max = 0;
+        int trail_chance = 100;
+
     public:
         // Used by generic_factory
         string_id<ammo_effect> id;

src/map.cpp

@@ -11,6 +11,7 @@
 #include <unordered_map>
 
 #include "ammo.h"
+#include "ammo_effect.h"
 #include "artifact.h"
 #include "avatar.h"
 #include "calendar.h"
@@ -3550,36 +3551,12 @@ void map::shoot( const tripoint &p, projectile &proj, const bool hit_items )
         dam = 0;
     }
 
-    if( ammo_effects.count( "TRAIL" ) && !one_in( 4 ) ) {
-        add_field( p, fd_smoke, rng( 1, 2 ) );
-    }
-
-    if( ammo_effects.count( "STREAM" ) && !one_in( 3 ) ) {
-        add_field( p, fd_fire, rng( 1, 2 ) );
-    }
-
-    if( ammo_effects.count( "STREAM_GAS_FUNGICIDAL" ) && !one_in( 3 ) ) {
-        add_field( p, fd_fungicidal_gas, rng( 1, 2 ) );
-    }
-
-    if( ammo_effects.count( "STREAM_GAS_INSCENTICIDAL" ) && !one_in( 3 ) ) {
-        add_field( p, fd_insecticidal_gas, rng( 1, 2 ) );
-    }
-
-    if( ammo_effects.count( "STREAM_BIG" ) && !one_in( 4 ) ) {
-        add_field( p, fd_fire, 2 );
-    }
-
-    if( ammo_effects.count( "LIGHTNING" ) ) {
-        add_field( p, fd_electricity, rng( 2, 3 ) );
-    }
-
-    if( ammo_effects.count( "PLASMA" ) && one_in( 2 ) ) {
-        add_field( p, fd_plasma, rng( 1, 2 ) );
-    }
-
-    if( ammo_effects.count( "LASER" ) || ammo_effects.count( "DRAW_LASER_BEAM" ) ) {
-        add_field( p, fd_laser, 2 );
+    for( const ammo_effect &ae : ammo_effects::get_all() ) {
+        if( ammo_effects.count( ae.id.str() ) > 0 ) {
+            if( x_in_y( ae.trail_chance, 100 ) ) {
+                g->m.add_field( p, ae.trail_field_type, rng( ae.trail_intensity_min, ae.trail_intensity_max ) );
+            }
+        }
     }
 
     dam = std::max( 0.0f, dam );