add basic heightmaps generator optimization

src/logic/scripting/lua/lua_type_heightmap.cpp

@@ -166,6 +166,19 @@ static int l_resize(lua::State* L) {
     return 0;
 }
 
+static int l_crop(lua::State* L) {
+    if (auto heightmap = touserdata<LuaHeightmap>(L, 1)) {
+        uint srcX = touinteger(L, 2);
+        uint srcY = touinteger(L, 3);
+
+        uint dstWidth = touinteger(L, 4);
+        uint dstHeight = touinteger(L, 5);
+
+        heightmap->getHeightmap()->crop(srcX, srcY, dstWidth, dstHeight);
+    }
+    return 0;
+}
+
 static std::unordered_map<std::string, lua_CFunction> methods {
     {"dump", lua::wrap<l_dump>},
     {"noise", lua::wrap<l_noise<FNL_NOISE_OPENSIMPLEX2>>},
@@ -177,6 +190,7 @@ static std::unordered_map<std::string, lua_CFunction> methods {
     {"max", lua::wrap<l_binop_func<util::max>>},
     {"abs", lua::wrap<l_unaryop_func<util::abs>>},
     {"resize", lua::wrap<l_resize>},
+    {"crop", lua::wrap<l_crop>},
 };
 
 static int l_meta_meta_call(lua::State* L) {

src/maths/Heightmap.cpp

@@ -1,6 +1,7 @@
 #include "Heightmap.hpp"
 
 #include <cmath>
+#include <cstring>
 #include <stdexcept>
 #include <glm/glm.hpp>
 
@@ -59,6 +60,9 @@ static inline float sample_at(
 void Heightmap::resize(
     uint dstwidth, uint dstheight, InterpolationType interp
 ) {
+    if (width == dstwidth && height == dstheight) {
+        return;
+    }
     std::vector<float> dst;
     dst.resize(dstwidth*dstheight);
 
@@ -75,3 +79,29 @@ void Heightmap::resize(
     height = dstheight;
     buffer = std::move(dst);
 }
+
+void Heightmap::crop(
+    uint srcx, uint srcy, uint dstwidth, uint dstheight
+) {
+    if (srcx + dstwidth > width || srcy + dstheight > height) {
+        throw std::runtime_error(
+            "crop zone is not fully inside of the source image");
+    }
+    if (dstwidth == width && dstheight == height) {
+        return;
+    }
+
+    std::vector<float> dst;
+    dst.resize(dstwidth*dstheight);
+
+    for (uint y = 0; y < dstheight; y++) {
+        std::memcpy(
+            dst.data()+y*dstwidth, 
+            buffer.data()+(y+srcy)*width+srcx, 
+            dstwidth*sizeof(float));
+    }
+
+    width = dstwidth;
+    height = dstheight;
+    buffer = std::move(dst);
+}

src/maths/Heightmap.hpp

@@ -27,6 +27,8 @@ public:
 
     void resize(uint width, uint height, InterpolationType interpolation);
 
+    void crop(uint srcX, uint srcY, uint dstWidth, uint dstHeight);
+
     uint getWidth() const {
         return width;
     }

src/world/generator/WorldGenerator.cpp

@@ -34,6 +34,7 @@ void WorldGenerator::generate(
         for (uint x = 0; x < CHUNK_W; x++) {
             // generate water
             int height = values[z * CHUNK_W + x] * CHUNK_H;
+            height = std::max(0, height);
             for (uint y = height+1; y <= seaLevel; y++) {
                 voxels[vox_index(x, y, z)].id = baseWater;
             }