Add TRANSLUCENT terrain flag which blocks vision but not light

data/json/furniture_and_terrain/terrain-doors.json

@@ -3086,7 +3086,7 @@
     "connect_groups": "WALL",
     "connects_to": "WALL",
     "rotates_to": "INDOORFLOOR",
-    "flags": [ "DOOR", "NOITEM", "BLOCK_WIND", "SUPPORTS_ROOF" ],
+    "flags": [ "DOOR", "NOITEM", "BLOCK_WIND", "SUPPORTS_ROOF", "TRANSLUCENT" ],
     "open": "t_door_glass_frosted_o",
     "copy-from": "t_door_glass_c"
   },
@@ -3101,7 +3101,7 @@
     "connect_groups": "WALL",
     "connects_to": "WALL",
     "rotates_to": "INDOORFLOOR",
-    "flags": [ "DOOR", "NOITEM", "SUPPORTS_ROOF" ],
+    "flags": [ "DOOR", "NOITEM", "SUPPORTS_ROOF", "TRANSLUCENT" ],
     "open": "t_door_glass_frosted_lab_o",
     "copy-from": "t_door_glass_frosted_c"
   },

data/json/furniture_and_terrain/terrain-windows.json

@@ -1019,6 +1019,7 @@
       "BLOCK_WIND",
       "REDUCE_SCENT",
       "WINDOW",
+      "TRANSLUCENT",
       "SUPPORTS_ROOF"
     ],
     "bash": {
@@ -1051,6 +1052,7 @@
       "BLOCK_WIND",
       "REDUCE_SCENT",
       "WINDOW",
+      "TRANSLUCENT",
       "SUPPORTS_ROOF"
     ],
     "bash": {
@@ -1083,6 +1085,7 @@
       "BLOCK_WIND",
       "REDUCE_SCENT",
       "WINDOW",
+      "TRANSLUCENT",
       "SUPPORTS_ROOF"
     ],
     "bash": {

doc/JSON_FLAGS.md

@@ -701,6 +701,7 @@ List of known flags, used in both `furniture` and `terrain`.  Some work for both
 - ```TRANSLOCATOR``` Tile is a translocator gate, for purposes of the `translocator` examine action.
 - ```TRANSPARENT_FLOOR``` This terrain allows light to the z-level below.
 - ```TRANSPARENT``` Players and monsters can see through/past it.  Also sets ter_t.transparent.
+- ```TRANSLUCENT``` Player and monsters can't see through/past it, but it can pass the light
 - ```UNSTABLE``` Walking here cause the bouldering effect on the character.
 - ```USABLE_FIRE``` This terrain or furniture counts as a nearby fire for crafting.
 - ```WALL``` This terrain is an upright obstacle.  Used for fungal conversion, and also implies `CONNECT_WITH_WALL`.

src/lightmap.cpp

@@ -152,7 +152,8 @@ bool map::build_transparency_cache( const int zlev )
                     // Fields are either transparent or not, however we want some to be translucent
                     value = value * i_level.translucency;
                 }
-                // TODO: [lightmap] Have glass reduce light as well
+                // TODO: [lightmap] Have glass reduce light as well.
+                // Note, binary transluceny is implemented in build_vision_transparency_cache below
                 return std::make_pair( value, value_wo_fields );
             };
 
@@ -208,6 +209,8 @@ bool map::build_vision_transparency_cache( const int zlev )
 
     bool dirty = false;
 
+    // This segment handles vision when the player is crouching or prone. It only checks adjacent tiles.
+    // If you change this, also consider creature::sees and map::obstacle_coverage.
     bool is_crouching = player_character.is_crouching();
     bool low_profile = player_character.has_effect( effect_quadruped_full ) &&
                        player_character.is_running();
@@ -229,6 +232,19 @@ bool map::build_vision_transparency_cache( const int zlev )
         }
     }
 
+    // This segment handles blocking vision through TRANSLUCENT flagged terrain.
+    // 60 tile radius should cover all potentially visible tiles.
+    // magical number, TODO replace when Eso finish reality bub things
+    for( const tripoint &loc : points_in_radius( p, 60 ) ) {
+        if( loc == p ) {
+            // The tile player is standing on should always be visible
+            vision_transparency_cache[p.x][p.y] = LIGHT_TRANSPARENCY_OPEN_AIR;
+        } else if( map::ter( loc ).obj().has_flag( ter_furn_flag::TFLAG_TRANSLUCENT ) ) {
+            vision_transparency_cache[loc.x][loc.y] = LIGHT_TRANSPARENCY_SOLID;
+            dirty = true;
+        }
+    }
+
     return dirty;
 }
 

src/mapdata.cpp

@@ -260,8 +260,9 @@ std::string enum_to_string<ter_furn_flag>( ter_furn_flag data )
         case ter_furn_flag::TFLAG_TRANSPARENT_FLOOR: return "TRANSPARENT_FLOOR";
         case ter_furn_flag::TFLAG_TOILET_WATER: return "TOILET_WATER";
         case ter_furn_flag::TFLAG_ELEVATOR: return "ELEVATOR";
-		case ter_furn_flag::TFLAG_ACTIVE_GENERATOR: return "ACTIVE_GENERATOR";
-		case ter_furn_flag::TFLAG_NO_FLOOR_WATER: return "NO_FLOOR_WATER";
+        case ter_furn_flag::TFLAG_ACTIVE_GENERATOR: return "ACTIVE_GENERATOR";
+        case ter_furn_flag::TFLAG_TRANSLUCENT: return "TRANSLUCENT";
+        case ter_furn_flag::TFLAG_NO_FLOOR_WATER: return "NO_FLOOR_WATER";
         case ter_furn_flag::TFLAG_GRAZABLE: return "GRAZABLE";
         case ter_furn_flag::TFLAG_GRAZER_INEDIBLE: return "GRAZER_INEDIBLE";
         case ter_furn_flag::TFLAG_BROWSABLE: return "BROWSABLE";
@@ -679,7 +680,8 @@ void load_terrain( const JsonObject &jo, const std::string &src )
 
 void map_data_common_t::extraprocess_flags( const ter_furn_flag flag )
 {
-    if( !transparent && flag == ter_furn_flag::TFLAG_TRANSPARENT ) {
+    if( !transparent && ( flag == ter_furn_flag::TFLAG_TRANSPARENT ||
+                          flag == ter_furn_flag::TFLAG_TRANSLUCENT ) ) {
         transparent = true;
     }
 

src/mapdata.h

@@ -134,6 +134,7 @@ struct plant_data {
 /*
  * List of known flags, used in both terrain.json and furniture.json.
  * TRANSPARENT - Players and monsters can see through/past it. Also sets ter_t.transparent
+ * TRANSLUCENT - Must be paired with TRANSPARENT. Allows light to pass through, but blocks vision.
  * FLAT - Player can build and move furniture on
  * CONTAINER - Items on this square are hidden until looted by the player
  * PLACE_ITEM - Valid terrain for place_item() to put items on
@@ -201,6 +202,7 @@ struct plant_data {
  */
 enum class ter_furn_flag : int {
     TFLAG_TRANSPARENT,
+    TFLAG_TRANSLUCENT,
     TFLAG_FLAMMABLE,
     TFLAG_REDUCE_SCENT,
     TFLAG_SWIMMABLE,

tests/vision_test.cpp

@@ -45,6 +45,7 @@ static const ter_str_id ter_t_flat_roof( "t_flat_roof" );
 static const ter_str_id ter_t_floor( "t_floor" );
 static const ter_str_id ter_t_utility_light( "t_utility_light" );
 static const ter_str_id ter_t_window_frame( "t_window_frame" );
+static const ter_str_id ter_t_window_stained_green( "t_window_stained_green" );
 
 static const trait_id trait_MYOPIC( "MYOPIC" );
 
@@ -125,6 +126,7 @@ static const tile_predicate set_up_tiles_common =
     ifchar( '#', ter_set( ter_t_brick_wall ) + ter_set_flat_roof_above ) ||
     ifchar( '=', ter_set( ter_t_window_frame ) + ter_set_flat_roof_above ) ||
     ifchar( '-', ter_set( ter_t_floor ) + ter_set_flat_roof_above ) ||
+    ifchar( 'G', ter_set( ter_t_window_stained_green ) + ter_set_flat_roof_above ) ||
     fail;
 
 struct vision_test_flags {
@@ -424,6 +426,27 @@ TEST_CASE( "vision_crouching_blocks_vision_but_not_light", "[shadowcasting][visi
     t.test_all();
 }
 
+TEST_CASE( "vision_translucent_blocks_vision_but_not_light", "[shadowcasting][vision]" )
+{
+    vision_test_case t{
+        {
+            "###",
+            "#u#",
+            "#G#",
+            "   ",
+        },
+        {
+            "444",
+            "444",
+            "444",
+            "666",
+        },
+        day_time
+    };
+
+    t.test_all();
+}
+
 TEST_CASE( "vision_see_wall_in_moonlight", "[shadowcasting][vision]" )
 {
     const time_point full_moon = calendar::turn_zero + calendar::season_length() / 6;