From 8fb0f6a1bbe8dacb815921dfdf9360972582158f Mon Sep 17 00:00:00 2001
From: MihailRis <mexaruc@gmail.com>
Date: Sun, 18 Aug 2024 00:08:36 +0300
Subject: [PATCH] add basic heightmaps generator optimization

---
 res/generators/default.lua                    | 39 +++++++++++++------
 .../scripting/lua/lua_type_heightmap.cpp      | 14 +++++++
 src/maths/Heightmap.cpp                       | 30 ++++++++++++++
 src/maths/Heightmap.hpp                       |  2 +
 src/world/generator/WorldGenerator.cpp        |  1 +
 5 files changed, 74 insertions(+), 12 deletions(-)

diff --git a/res/generators/default.lua b/res/generators/default.lua
index 38c33ed0..22f7e9a0 100644
--- a/res/generators/default.lua
+++ b/res/generators/default.lua
@@ -7,34 +7,49 @@ layers = {
     {block="base:bazalt", height=1},
 }
 
-function generate_heightmap(x, y, w, h, seed)
+local function _generate_heightmap(x, y, w, h, seed, s)
     local umap = Heightmap(w, h)
     local vmap = Heightmap(w, h)
     umap.noiseSeed = seed
     vmap.noiseSeed = seed
-    umap:noise({x+521, y+73}, 0.05, 1, 20.8)
-    umap:noise({x+51, y+75}, 0.05, 1, 21.8)
-    vmap:noise({x+521, y+70}, 0.1, 3, 35.8)
-    vmap:noise({x+95, y+246}, 0.15, 3, 35.8)
+    vmap:noise({x+521, y+70}, 0.1*s, 3, 25.8)
+    vmap:noise({x+95, y+246}, 0.15*s, 3, 25.8)
 
     local map = Heightmap(w, h)
     map.noiseSeed = seed
-    map:noise({x, y}, 0.02, 7, 0.2)
-    map:noise({x, y}, 0.06, 8, 0.4, umap, vmap)
+    map:noise({x, y}, 0.8*s, 4, 0.04)
+    map:cellnoise({x, y}, 0.1*s, 3, 0.7, umap, vmap)
     map:mul(0.5)
-    map:add(0.1)
-    map:pow(2.0)
+    map:add(0.3)
 
     local rivermap = Heightmap(w, h)
     rivermap.noiseSeed = seed
-    rivermap:noise({x+21, y+12}, 0.1, 4)
+    rivermap:noise({x+21, y+12}, 0.1*s, 4)
     rivermap:abs()
     rivermap:mul(2.0)
-    rivermap:pow(0.4)
+    rivermap:pow(0.3)
     rivermap:max(0.6)
     map:add(0.4)
     map:mul(rivermap)
-    map:add(-0.2)
+    map:add(-0.15)
 
     return map
 end
+
+function generate_heightmap(x, y, w, h, seed)
+    -- blocks per dot
+    -- 8 - linear interpolation is visible, but not so much (Minecraft)
+    -- 4 - high quality, but slower
+    -- 2 - you really don't need it
+    -- 1 - please have mercy on your CPU
+    local bpd = 8
+    local map = _generate_heightmap(
+        math.floor(x/bpd), math.floor(y/bpd), 
+        math.floor(w/bpd)+1, math.floor(h/bpd)+1, seed, bpd)
+    map:resize(w+bpd, h+bpd, 'linear')
+    map:crop(0, 0, w, h)
+    return map
+end
+
+local map = generate_heightmap(0, 0, 1024, 1024, 0)
+map:dump("heightmap.png")
diff --git a/src/logic/scripting/lua/lua_type_heightmap.cpp b/src/logic/scripting/lua/lua_type_heightmap.cpp
index ebc58952..e5fd46ac 100644
--- a/src/logic/scripting/lua/lua_type_heightmap.cpp
+++ b/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) {
diff --git a/src/maths/Heightmap.cpp b/src/maths/Heightmap.cpp
index 5b7996a7..165c0040 100644
--- a/src/maths/Heightmap.cpp
+++ b/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);
+}
diff --git a/src/maths/Heightmap.hpp b/src/maths/Heightmap.hpp
index f8185f4c..5b9f4cfa 100644
--- a/src/maths/Heightmap.hpp
+++ b/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;
     }
diff --git a/src/world/generator/WorldGenerator.cpp b/src/world/generator/WorldGenerator.cpp
index d92050a8..fa25d49d 100644
--- a/src/world/generator/WorldGenerator.cpp
+++ b/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;
             }