added structure renderer.

src/main/java/carpet/script/CarpetScriptServer.java

@@ -43,6 +43,7 @@ public class CarpetScriptServer
 
     private static final List<Module> bundledModuleData = new ArrayList<Module>(){{
         add(new BundledModule("camera", false));
+        add(new BundledModule("structures", false));
         add(new BundledModule("event_test", false));
         add(new BundledModule("stats_test", false));
         add(new BundledModule("math", true));

src/main/java/carpet/script/Expression.java

@@ -1312,7 +1312,7 @@ public class Expression
             LazyValue boundedLHS;
             if (v1 instanceof ListValue || v1 instanceof MapValue)
             {
-                ((ListValue) v1).append(v2);
+                ((AbstractListValue) v1).append(v2);
                 boundedLHS = (cc, tt)-> v1;
             }
             else

src/main/resources/assets/carpet/scripts/structures.sc

@@ -0,0 +1,78 @@
+import('math', '_euclidean_sq', '_euclidean');
+
+global_current_structures = m();
+global_overlay_active = false;
+global_range = 3;
+global_max_pieces = 4;
+
+__command() -> '';
+
+monument() -> __toggle('monument');
+fortress() -> __toggle('fortress');
+mansion() -> __toggle('mansion');
+jungle_temple() -> __toggle('jungle_temple');
+desert_temple() -> __toggle('desert_temple');
+end_city() -> __toggle('end_city');
+igloo() -> __toggle('igloo');
+shipwreck() -> __toggle('shipwreck');
+witch_hut() -> __toggle('witch_hut');
+stronghold() -> __toggle('stronghold');
+ocean_ruin() -> __toggle('ocean_ruin');
+treasure() -> __toggle('treasure');
+pillager_outpost() -> __toggle('pillager_outpost');
+mineshaft() -> __toggle('mineshaft');
+village() -> __toggle('village');
+
+__toggle(structure) ->
+(
+    p = player()
+    if( has(global_current_structures:structure),
+        delete(global_current_structures:structure);
+        'disabled '+structure+' overlays';
+    ,
+        global_current_structures:structure = null;
+        if (!global_overlay_active, __structure_renderer(p~'name'));
+        'enabled '+structure+' overlays';
+    )
+);
+
+__structure_renderer(player_name) ->
+(
+    if (length(global_current_structures)==0, global_overlay_active = false; return());
+    p = player(player_name);
+    if (!p, global_overlay_active = false; return());
+    global_overlay_active = true;
+	in_dimension(p,
+	    ppos = pos(p);
+	    starts = m();
+		for(range(-global_range,global_range), cx =_;
+			for (range(-global_range,global_range), cz = _;
+				ref_pos = ppos + l(16*cx,0,16*cz);
+				for(filter(structure_references(ref_pos), has(global_current_structures:_)),
+				    name = _;
+				    for(structure_references(ref_pos, name),
+				        starts += l(_, name);
+				    )
+				)
+			)
+		);
+		for (starts, l(position, name) = _;
+		    structure_data = structures(position):name;
+		    if (!structure_data, continue()); // messed up references - shouldn't happen
+		    structure_pieces = structures(position, name);
+		    if (!structure_pieces, continue()); // messed up references - shouldn't happen
+		    l(from, to) = structure_data;
+		    total_size = _euclidean(from, to);
+		    density = max(10, total_size/10);
+		    particle_rect('dust 0 1 1 2', from, to+1, density);
+		    structure_pieces = slice(sort_key(structure_pieces, _euclidean_sq((_:2+_:3)/2,ppos)), 0, global_max_pieces);
+		    for (structure_pieces, l(piece, direction, from, to) = _;
+		        factor = 1-_i/global_max_pieces/2;
+		        total_size = _euclidean(from, to);
+                density = max(_i+1, total_size/10);
+		        particle_rect(str('dust %.2f %.2f 1 1',factor, factor), from, to+1, density);
+		    )
+		)
+	);
+	schedule(3, '__structure_renderer', player_name);
+);