add 'below_sea_level' layer property

res/generators/default.lua

@@ -1,6 +1,6 @@
 layers = {
-    {block="base:grass_block", height=1},
-    {block="base:dirt", height=1},
+    {block="base:grass_block", height=1, below_sea_level=false},
+    {block="base:dirt", height=5, below_sea_level=false},
     {block="base:stone", height=-1},
     {block="base:bazalt", height=1},
 }

src/logic/scripting/scripting.cpp

@@ -748,7 +748,13 @@ std::unique_ptr<GeneratorScript> scripting::load_generator(
                 lua::pop(L);
                 lua::requirefield(L, "height");
                 int height = lua::tointeger(L, -1);
-                lua::pop(L, 2);
+                lua::pop(L);
+                bool below_sea_level = true;
+                if (lua::getfield(L, "below_sea_level")) {
+                    below_sea_level = lua::toboolean(L, -1);
+                    lua::pop(L);
+                }
+                lua::pop(L);
 
                 if (hasResizeableLayer) {
                     lastLayersHeight += height;
@@ -759,7 +765,7 @@ std::unique_ptr<GeneratorScript> scripting::load_generator(
                     }
                     hasResizeableLayer = true;
                 }
-                layers.push_back(BlocksLayer {name, height, {}});
+                layers.push_back(BlocksLayer {name, height, below_sea_level, {}});
             } catch (const std::runtime_error& err) {
                 lua::pop(L, 2);
                 throw std::runtime_error(

src/world/generator/GeneratorDef.hpp

@@ -11,6 +11,7 @@ class Content;
 struct BlocksLayer {
     std::string block;
     int height;
+    bool below_sea_level;
 
     struct {
         blockid_t id;

src/world/generator/WorldGenerator.cpp

@@ -16,10 +16,11 @@ WorldGenerator::WorldGenerator(
 
 #include "util/timeutil.hpp"
 void WorldGenerator::generate(voxel* voxels, int chunkX, int chunkZ, int seed) {
+    timeutil::ScopeLogTimer log(555);
     auto heightmap = def.script->generateHeightmap(
         {chunkX*CHUNK_W, chunkZ*CHUNK_D}, {CHUNK_W, CHUNK_D}
     );
-    timeutil::ScopeLogTimer log(555);
+    uint seaLevel = 64;
     auto values = heightmap->getValues();
     const auto& layers = def.script->getLayers();
     uint lastLayersHeight = def.script->getLastLayersHeight();
@@ -30,19 +31,27 @@ void WorldGenerator::generate(voxel* voxels, int chunkX, int chunkZ, int seed) {
     for (uint z = 0; z < CHUNK_D; z++) {
         for (uint x = 0; x < CHUNK_W; x++) {
             int height = values[z * CHUNK_W + x] * 255 + 10;
-            for (uint y = height+1; y < 64; y++) {
+            for (uint y = height+1; y <= seaLevel; y++) {
                 voxels[vox_index(x, y, z)].id = baseWater;
             }
 
             uint y = height;
+            uint layerExtension = 0;
             for (const auto& layer : layers) {
+                if (y < seaLevel && !layer.below_sea_level) {
+                    layerExtension = std::max(0, layer.height);
+                    continue;
+                }
                 uint layerHeight = layer.height;
                 if (layerHeight == -1) {
                     layerHeight = y - lastLayersHeight + 1;
+                } else {
+                    layerHeight += layerExtension;
                 }
                 for (uint i = 0; i < layerHeight; i++, y--) {
                     voxels[vox_index(x, y, z)].id = layer.rt.id;
                 }
+                layerExtension = 0;
             }
         }
     }