add plants

src/world/generator/GeneratorDef.hpp

@@ -35,15 +35,56 @@ struct BlocksLayers {
 
 struct BiomeParameter {
     /// @brief Central parameter value for the biome
-    float origin;
+    float value;
     /// @brief Parameter score multiplier 
-    /// (the higher the value, the greater the chance of biome choosing)
+    /// (the higher the weight, the greater the chance of biome choosing)
     float weight;
 };
 
+struct PlantEntry {
+    /// @brief Plant block id
+    std::string block;
+    /// @brief Plant weight
+    float weight;
+
+    struct {
+        blockid_t id;
+    } rt;
+};
+
+struct BiomePlants {
+    static inline float MIN_CHANCE = 0.000001f;
+
+    /// @brief Plant entries sorted by weight descending.
+    std::vector<PlantEntry> plants;
+    /// @brief Sum of weight values
+    float weightsSum;
+    /// @brief Plant generation chance
+    float chance;
+
+    /// @brief Choose plant based on weight
+    /// @param rand some random value in range [0, 1)
+    /// @return index of chosen plant block
+    inline blockid_t choose(float rand) const {
+        if (plants.empty() || rand > chance || chance < MIN_CHANCE) {
+            return 0;
+        }
+        rand = rand / chance;
+        rand *= weightsSum;
+        for (const auto& plant : plants) {
+            rand -= plant.weight;
+            if (rand <= 0.0f) {
+                return plant.rt.id;
+            }
+        }
+        return plants[plants.size()-1].rt.id;
+    }
+};
+
 struct Biome {
     std::string name;
     std::vector<BiomeParameter> parameters;
+    BiomePlants plants;
     BlocksLayers groundLayers;
     BlocksLayers seaLayers;
 };

src/world/generator/WorldGenerator.cpp

@@ -3,6 +3,7 @@
 #include <cstring>
 #include <iostream>
 
+#include "maths/util.hpp"
 #include "content/Content.hpp"
 #include "voxels/Block.hpp"
 #include "voxels/Chunk.hpp"
@@ -63,7 +64,7 @@ static inline const Biome* choose_biome(
     for (const auto& biome : biomes) {
         float score = 0.0f;
         for (uint i = 0; i < paramsCount; i++) {
-            score += glm::abs((params[i] - biome.parameters[i].origin) / 
+            score += glm::abs((params[i] - biome.parameters[i].value) / 
                               biome.parameters[i].weight);
         }
         if (score < chosenScore) {
@@ -92,6 +93,9 @@ void WorldGenerator::generate(
 
     std::memset(voxels, 0, sizeof(voxel) * CHUNK_VOL);
 
+    PseudoRandom plantsRand;
+    plantsRand.setSeed(chunkX, chunkZ);
+
     for (uint z = 0; z < CHUNK_D; z++) {
         for (uint x = 0; x < CHUNK_W; x++) {
             const Biome* biome = choose_biome(biomes, biomeParams, x, z);
@@ -104,6 +108,15 @@ void WorldGenerator::generate(
 
             generate_pole(seaLayers, seaLevel, height, seaLevel, voxels, x, z);
             generate_pole(groundLayers, height, 0, seaLevel, voxels, x, z);
+            
+            if (height+1 > seaLevel) {
+                // TODO: add underwater plants support
+                float rand = (plantsRand.randU32() % RAND_MAX) / static_cast<float>(RAND_MAX);
+                blockid_t plant = biome->plants.choose(rand);
+                if (plant) {
+                    voxels[vox_index(x, height+1, z)].id = plant;
+                }
+            }
         }
     }
 }